User manual CELESTRON CGE MODELS

INSTRUCTION MANUAL CGE800 CGE925 CGE1100 CGE1400 INTRODUCTION..................................................................................................................................................................................4 Warning ..............................................................................................................................................................................................4 ASSEMBLY ...........................................................................................................................................................................................6 Setting up the Tripod...........................................................................................................................................................................6 Attaching the Center Leg Brace ..........................................................................................................................................................7 Attaching the Electronics Pier.............................................................................................................................................................7 Attaching the Equatorial Mount ..........................................................................................................................................................8 Installing the Counterweight Bar ........................................................................................................................................................8 Installing the Counterweight ...............................................................................................................................................................8 Attaching the Optical Tube to the Mount............................................................................................................................................9 Attaching the Visual Back...................................................................................................................................................................9 Installing the Star Diagonal...............................................................................................................................................................10 Installing the Eyepiece ......................................................................................................................................................................10 Installing the Finderscope .................................................................................................................................................................11 Moving the Telescope Manually.......................................................................................................................................................12 Adjusting the Mount .........................................................................................................................................................................12 Balancing The Mount in R.A. ...........................................................................................................................................................13 Balancing The Mount in DEC...........................................................................................................................................................13 Attaching the Motor Cables ..............................................................................................................................................................14 Powering the Telescope ....................................................................................................................................................................14 Transporting the CGE .......................................................................................................................................................................14 HAND CONTROL...............................................................................................................................................................................16 Named Stars ......................................................................................................................................................................................17 Hand Control Operation ....................................................................................................................................................................17 Alignment Procedures.......................................................................................................................................................................18 Startup Procedure..............................................................................................................................................................................18 Auto Two-Star Align ........................................................................................................................................................................19 Auto One-Star Align .........................................................................................................................................................................19 Quick-Align ......................................................................................................................................................................................20 Last Alignment .................................................................................................................................................................................20 CGE Re-Alignment...........................................................................................................................................................................20 Object Catalog ..................................................................................................................................................................................21 Selecting an Object............................................................................................................................................................................21 Slewing to an Object .........................................................................................................................................................................21 Finding Planets..................................................................................................................................................................................21 Tour Mode.........................................................................................................................................................................................22 Constellation Tour.............................................................................................................................................................................22 Direction Buttons ..............................................................................................................................................................................22 Rate Button........................................................................................................................................................................................22 Setup Procedures...............................................................................................................................................................................23 Tracking Mode........................................................................................................................................................................23 Tracking Rate..........................................................................................................................................................................23 Date/Time ...............................................................................................................................................................................23 User Defined Objects ..............................................................................................................................................................24 Get RA/DEC ...........................................................................................................................................................................24 Goto R.A/Dec..........................................................................................................................................................................24 Identify....................................................................................................................................................................................24 Precise GoTo .....................................................................................................................................................................................25 Scope Setup Features.........................................................................................................................................................................25 Steup Time-Site.......................................................................................................................................................................25 Anti-backlash ..........................................................................................................................................................................25 Filter Limits ............................................................................................................................................................................26 Direction Buttons ....................................................................................................................................................................26 Goto Approach........................................................................................................................................................................26 Autoguide Rates......................................................................................................................................................................26 Mount Settings ........................................................................................................................................................................26 Utility Features ..................................................................................................................................................................................27 Calibrate Mount ......................................................................................................................................................................27 Move to Switch .......................................................................................................................................................................27 Home Position.........................................................................................................................................................................27 Polar Align ..............................................................................................................................................................................27 Periodic Error Correction ........................................................................................................................................................28 Light Control...........................................................................................................................................................................28 Factory Settings.......................................................................................................................................................................28 Version....................................................................................................................................................................................28 Get Alt-Az...............................................................................................................................................................................28 Goto Alt-Az ............................................................................................................................................................................28 Hibernate.................................................................................................................................................................................28 Turn On/Off RTC....................................................................................................................................................................28 Turn On/Off GPS ....................................................................................................................................................................29 Image Orientation..............................................................................................................................................................................31 Focusing ............................................................................................................................................................................................32 Calculating Magnification .................................................................................................................................................................32 Determining Field of View................................................................................................................................................................32 General Observing Hints ...................................................................................................................................................................33 ASTRONOMY BASICS......................................................................................................................................................................34 The Celestial Coordinate System.......................................................................................................................................................34 Motion of the Stars ............................................................................................................................................................................35 Finding the North Celestial Pole........................................................................................................................................................37 Declination Drift Method of Polar Alignment ...................................................................................................................................38 CELESTIAL OBSERVING................................................................................................................................................................39 Observing the Moon ..........................................................................................................................................................................39 Lunar Observing Hints ......................................................................................................................................................................39 Observing the Planets ........................................................................................................................................................................39 Observing the Sun .............................................................................................................................................................................40 Solar Observing Hints .......................................................................................................................................................................40 Observing Deep Sky Objects.............................................................................................................................................................40 Seeing Conditions..............................................................................................................................................................................40 Transparency .....................................................................................................................................................................................40 Sky Illumination ................................................................................................................................................................................40 Seeing................................................................................................................................................................................................41 ASTROPHOTOGRAPHY ..................................................................................................................................................................42 Short Exposure Prime Focus Photography ........................................................................................................................................42 Eyepiece Projection ...........................................................................................................................................................................43 Long Exposure Prime Focus Photography.........................................................................................................................................44 Periodic Error Correction (PEC)........................................................................................................................................................45 Using Periodic Error Correction ........................................................................................................................................................46 Terrestrial Photography .....................................................................................................................................................................47 Metering ............................................................................................................................................................................................47 Reducing Vibration ...........................................................................................................................................................................47 CCD Imaging ....................................................................................................................................................................................47 Fastar F/2 Imaging............................................................................................................................................................................49 F/6.3 with Reducer/Corrector ............................................................................................................................................................50 Medium size to small galaxies ­........................................................................................................................................................50 Planetary or Lunar-- ..........................................................................................................................................................................50 Auto Guiding.....................................................................................................................................................................................51 TELESCOPE MAINTENANCE ........................................................................................................................................................52 Care and Cleaning of the Optics ........................................................................................................................................................52 Collimation........................................................................................................................................................................................52 OPTIONAL ACCESSORIES............................................................................................................................................................54 TECHNICAL SPECIFICATIONS....................................................................................................................................................57 APPENDIX A ­ LONGITUDES AND LATITUDES........................................................................................................................59 APPENDIX B ­ RS-232 CONNECTION...........................................................................................................................................64 APPENDIX C ­ TIME ZONE MAP ..................................................................................................................................................66 SKY MAPS...........................................................................................................................................................................................68 3 Congratulations on your purchase of the Celestron CGE telescope! The CGE ushers in the next generation of computer automated telescopes. The Celestron CGE series continues in this proud tradition combining large aperture optics with the sophistication and ease of use of our computerized GoTo mount. If you are new to astronomy, you may wish to start off by using the CGE's built-in Sky Tour feature, which commands the CGE to find the most interesting objects in the sky and automatically slews to each one. Or if you are an experienced amateur, you will appreciate the comprehensive database of over 40,000 objects, including customized lists of all the best deep-sky objects, bright double stars and variable stars. No matter at what level you are starting out, the CGE will unfold for you and your friends all the wonders of the Universe. Some of the many standard features of the CGE include: · · · · Fully enclosed optical encoders for position location. Ergonomically designed mount that disassembles into compact and portable pieces Database filter limits for creating custom object lists. Storage for programmable user defined objects; and Many other high performance features! The CGE's deluxe features combine with Celestron's legendary Schmidt-Cassegrain optical system to give amateur astronomers the most sophisticated and easy to use telescopes available on the market today. Take time to read through this manual before embarking on your journey through the Universe. It may take a few observing sessions to become familiar with your CGE, so you should keep this manual handy until you have fully mastered your telescope's operation. The CGE hand control has built-in instructions to guide you through all the alignment procedures needed to have the telescope up and running in minutes. Use this manual in conjunction with the on-screen instructions provided by the hand control. The manual gives detailed information regarding each step as well as needed reference material and helpful hints guaranteed to make your observing experience as simple and pleasurable as possible. Your CGE telescope is designed to give you years of fun and rewarding observations. However, there are a few things to consider before using your telescope that will ensure your safety and protect your equipment. Warning Y Y Never look directly at the sun with the naked eye or with a telescope (unless you have the proper solar filter). Permanent and irreversible eye damage may result. Never use your telescope to project an image of the sun onto any surface. Internal heat build-up can damage the telescope and any accessories attached to it. Y Never use an eyepiece solar filter or a Herschel wedge. Internal heat build-up inside the telescope can cause these devices to crack or break, allowing unfiltered sunlight to pass through to the eye. Never leave the telescope unsupervised, either when children are present or adults who may not be familiar with the correct operating procedures of your telescope. 4 Figure 2.1 - The CGE Telescope ASSE (CGE 1400 Shown) 1 2 3 4 5 6 7 Schmidt Corrector Lens Optical Tube Finderscope Eyepiece Star Diagonal Declination Clutch Lock Latitude Adjustment Scale 8 9 10 11 12 13 14 15 E F G H 5 I Control Panel (see below) Hand Control Holder / Strap Hand Control Tripod Tripod Center Leg Brace Counterweights Counterweight Bar R.A. Clutch Lock 12v Output Jack On/Off Switch Auxiliary Port 1 Auxiliary Port 2 Hand Control Port A B C D CONTROL PANEL Dec Motor Port R.A. Motor Port PC Interface Port Auto Guider Port This section covers the assembly instructions for your Celestron CGE telescope. The CGE telescope should be set up indoors the first time so that it is easy to identify the various parts and familiarize yourself with the correct assembly procedure before attempting it outdoors. Eyepiece Diagonal Finderscope Power Supply Counterweight CGE 800 (#11058) 25mm Plossl Eyepiece - 1.25" Star Diagonal - 1.25" 6x30 with Bracket Car Battery Adapter One - 11 lb. CGE 925 (#11059) 25mm Plossl Eyepiece - 1.25" Star Diagonal - 1.25" 6x30 with Bracket Car Battery Adapter One - 25 lb. CGE 1100 (#11061) 40mm Plossl Eyepiece - 1.25" Star Diagonal - 1.25" 9x50 with Bracket Car Battery Adapter One - 25 lb. CGE 1400 (#11063) 40mm Eyepiece - 2" Mirror Diagonal ­2" 9x50 with Bracket Car Battery Adapter Two ­ 25 lb. The Celestron CGE telescopes are shipped in four boxes (the CGE 1400 comes in five boxes). In separate boxes are the following: · · · · Optical Tube Assembly and Standard Accessories Equatorial Mount, Electronic Pier, Hand Control and Counterweight Bar Super HD Tripod Counterweight(s) Remove all the pieces from their respective boxes and place on a flat, clear work area. A large floor space is ideal. When setting up your Celestron telescope you must start with the tripod and work up from there. These instructions are laid out in the order each task must be performed. Setting up the Tripod The tripod legs attach to the electronics pier which together form the tripod to which the equatorial mount attaches. The tripod comes with two leg support brackets; a collapsible one that is already attached to the lower legs and a removable one that must be attached. To set up the tripod: 1. 2. 3. Stand the tripod vertically on a level surface, with the feet facing down. Grab the lower portion of two of the tripod legs and lift them slightly off the ground so that the tripod is resting on the third leg. Extend the tripod legs by pulling the tripod legs apart until the collapsible leg bracket is fully extended. Before the tripod is ready to support the equatorial head and optical tube the center leg support brace must first be installed. 6 Electronincs Pier Hand Control Holder Tripod Leg Center Leg Brace Figure 2-2 Attaching the Center Leg Brace For maximum rigidity, the Super HD Tripod has a center leg brace that installs on to the threaded rod below the tripod head. This brace fits snugly against the tripod legs, increasing stability while reducing vibration and flexure. To attach the center leg brace: 1. 2. 3. Unscrew the tension knob from the threaded rod beneath the tripod head. Place the center leg brace onto the threaded rod so that the cup on the end of each bracket contours to the curve of the tripod legs. Rotate the tension knob back on the threaded rod until the brace is very snug against each tripod leg. Attaching the Electronics Pier Before the equatorial mount head can be installed, the electronics pier must be attached to the tripod. To attach the pier: 1. 2. 3. Position the central column so that the electronics module is right side up (with the printing readable). Place the lower end of the central column over the tripod head. Rotate the column until the three holes line up with the threaded holes on the side of the tripod head. The electronics console should be positioned directly between two of the tripod leg hinges to provide easy access to it even when the counterweight bar and counterweight(s) are attached. Insert the three 3/8-16 button head cap screws provided through the holes in the electronics pier and into the tripod head. 7 4. 5. Tighten the screws to hold the column securely in place. Attaching the Equatorial Mount After the tripod is set up, you are ready to attach the equatorial mount. The equatorial mount is the platform to which the telescope attaches and allows you to move the telescope in right ascension and declination. To attach the equatorial mount to the tripod: 1. 2. 3. 4. Insert the base of the equatorial mount into the top of the electronics pier. Rotate the equatorial mount on the electronics pier until the holes in the mount line up with those in the pier and the dec opening (where the counterweight shaft will go) is positioned directly over one of the tripod legs. Insert the three remaining 3/8-16 cap screws and washers provided through the holes in the central pier and into the equatorial mount. Tighten the screws to hold the equatorial mount in place. Installing the Counterweight Bar To properly balance the telescope, the mount comes with a counterweight bar and at least one counterweight (depending on model). The counterweight bar is located in the same box as the Equatorial Mount Head --in a cutout along the bottom of the shipping box. To install the counterweight bar: 1. 2. Locate the opening in the equatorial mount on the DEC axis It is opposite the telescope mounting platform. Thread the counterweight bar into the opening until tight. Once the bar is securely in place you are ready to attach the counterweight. Dec Axis Counterweight Bar Figure 2-3 Since the fully assembled telescope is quite heavy, position the mount so that the tripod leg with the counterweight bar over it is pointing towards north before the tube assembly and counterweights are attached. This will make the polar alignment procedure much easier. Installing the Counterweight Depending on which CGE telescope you have, you will receive either one or two counterweights. To install the counterweight(s): 1. 2. Orient the mount so that the counterweight bar points toward the ground . Remove the counterweight safety thumbscrew and washer on the end of the counterweight bar (i.e., opposite the end that attaches to the mount). Loosen the locking screw on the side of the counterweight. Slide the counterweight onto the shaft. 8 Figure 2-4 Counterweight Locking Screw Safety Screw and Washer 3. 4. 5. 6. Tighten the locking screw on the side of the weight to hold the counterweight in place. Replace the counterweight safety thumbscrew and washer. Attaching the Optical Tube to the Mount The telescope attaches to the mount via a dovetail slide bar which is mounted along the bottom of the telescope tube. Before you attach the optical tube, make sure that the declination and right ascension clutch knobs are tight. This will ensure that the mount does not move suddenly while attaching the telescope. To mount the telescope tube: In order for the CGE mount to successfully locate its declination switches, the mounting platform must be positioned so that the dovetailed locking knobs are on the east side of the mount when polar aligned. In other words, when standing behind the mount facing north, the dovetail locking knobs should be on the right side of the mount. 1 2 3 Important! Dovetail Slide Bar Dovetail Locking Knobs Mounting Platform Figure 2-5 Loosen the locking knobs on the side of the telescope mounting platform. This allows you to slide the dovetail bar on the telescope onto the mount. Slide the dovetail bar on the telescope tube into the mounting platform of the mount. Slide the telescope so that the back of the dovetail bar is almost flush with the back of the mounting platform. Tighten the locking knobs on the side of the mounting platform to hold the telescope in place. Now that the optical tube is securely in place, the visual accessories can now be attached to the telescope. Attaching the Visual Back The visual back is the accessory that allows you to attach all visual accessories to the telescope. The CGE 1400 comes with a 2" mirror diagonal that attaches directly to the optical tube without the use of a visual back. To attach the visual back: 1. 2. 3. Remove the plastic cover on the rear cell. Place the knurled slip ring on the visual back over the threads on the rear cell. Hold the visual back with the set screw in a convenient position and rotate the knurled slip ring clockwise until tight. Once this is done, you are ready to attach other accessories, such as eyepieces, diagonal prisms, etc. If you want to remove the visual back, rotate the slip ring counterclockwise until it separates from the rear cell. 9 Installing the Star Diagonal The star diagonal is a prism that diverts the light at a right angle to the light path of the telescope. This allows you to observe in positions that are physically more comfortable than if you looked straight through. To attach the star diagonal onto a CGE 800, 925 or 1100: 1. 2. 3. Turn the set screw on the visual back until its tip no longer extends into (i.e., obstructs) the inner diameter of the visual back. Slide the chrome portion of the star diagonal into the visual back. Tighten the set screw on the visual back to hold the star diagonal in place. If you wish to change the orientation of the star diagonal, loosen the set screw on the visual back until the star diagonal rotates freely. Rotate the diagonal to the desired position and tighten the set screw. The CGE 1400 comes with a 2" mirror diagonal that attaches directly onto the rear threads of the 14" optical tube. See figure 2-6. Eyepiece 2" Barrel Eyepiece Star Diagonal Visual Back 2" thread-on Mirror Diagonal Figure 2-6 Figure 2-7 Installing the Eyepiece The eyepiece, or ocular, is an optical element that magnifies the image focused by the telescope. The eyepiece fits into either the visual back directly, the star diagonal, or the 2" mirror diagonal. To install an eyepiece: 1. Loosen the set screw on the star diagonal until the tip no longer extends into the inner diameter of the eyepiece end of the diagonal. 2. 3. Slide the chrome portion of the eyepiece into the star diagonal. Tighten the set screw on the star diagonal to hold the eyepiece in place. To remove the eyepiece, loosen the set screw on the star diagonal and slide the eyepiece out. You can replace it with another eyepiece (purchased separately). NOTE: The 2" mirror diagonal has a 1 1/4" eyepiece adapter to use 1 1/4" eyepieces. You may remove the adapter to use 2" eyepieces. Eyepieces are commonly referred to by focal length and barrel diameter. The focal length of each eyepiece is printed on the eyepiece barrel. The longer the focal length (i.e., the larger the number) the lower the eyepiece power and the shorter the 10 focal length (i.e., the smaller the number) the higher the magnification. Generally, you will use low-to-moderate power when viewing. For more information on how to determine power, see the section on "Calculating Magnification." Installing the Finderscope The CGE telescopes come with a 6x30 or 9x50 finderscope used to help you locate and center objects in the main field of your telescope. To accomplish this, the finder has a built-in cross-hair reticle that shows the optical center of the finderscope. Start by removing the finder and hardware from the plastic wrapper. Included are the following: · Finderscope · Finder Bracket · Rubber O-ring · Three Nylon Tipped Thumbscrews (10-24x1/2") · Two Phillips Head Screws (8-32x1/2" or 10-24x1/2") To install the finderscope: 1. Attach the bracket to the optical tube. To do this, place the curved portion of the bracket with the slot over the two holes in the rear cell. The bracket should be oriented so that the rings that hold the finder are over the telescope tube, not the rear cell (see Figure 2-8). Start threading the screws in by hand and tighten fully with an Allen wrench. Finderscope Nylon Adjustment Screw 2. Partially thread-in the three nylon-tipped thumbscrews that hold the finder in place inside the bracket. Tighten the screws until the nylon heads are flush with the inner diameter of the bracket ring. Do NOT thread them in completely or they will interfere with the placement of the finder. (Having the screws in place when the finder is installed will be easier than trying to insert the screws after the finder has been installed.) Slide the rubber O-ring over the back of the finder (it will NOT fit over the objective end of the finder). It may need to be stretched a little. Once on the main body of the finder, slide it up about one inch from the end of the finder. 3. Finder Bracket Figure 2-8 4. 5. 6. 7. 8. Rotate the finder until one cross hair is parallel to the R.A. axis and the other is parallel to the DEC axis. Slide the eyepiece end of the finder into the front of the bracket. Slightly tighten the three nylon tipped thumbscrews on the front ring of the bracket to hold the finder in place. Once on, push the finder back until the O-ring is snug inside the back ring of the finder bracket. Hand tighten the three nylon tipped thumbscrews until snug. 11 Moving the Telescope Manually In order to properly balance your telescope, you will need to move your telescope manually at various portions of the sky to observe different objects. To make rough adjustments, loosen the R.A. and DEC clutch knobs slightly and move the telescope in the desired direction. Both the R.A. and DEC axis have two knobs to clutch down each axis of the telescope. To loosen the clutches on the telescope, rotate the clutch knobs counterclockwise. Rotate the clutch knobs on each axis clockwise to lock the telescope in place. Adjusting the Mount In order for the clock drive to track accurately, the telescope's axis of rotation must be parallel to the Earth's axis of rotation, a process known as polar alignment. Polar alignment is achieved NOT by moving the telescope in R.A. or DEC, but by adjusting the mount vertically, which is called altitude, and horizontally, which is called azimuth. This section simply covers the correct movement of the telescope during the polar alignment process. The actual process of polar alignment, that is making the telescope's axis of rotation parallel to the Earth's, is described later in this manual in the section on "Polar Alignment." To adjust the mount in altitude: 1. 2. Locate the altitude adjustment bolt just above the tripod column (see figure 2-10). Using the 7/32" Allen wrench provided, turn the altitude adjustment bolt until the mount is at the right elevation. Figure 2-9 DEC Clutch Knob R.A. Clutch Knobs The total altitude range is from 13° to 65°. With the 23 lb counterweight attached to the counterweight shaft, the equatorial head can go as low as 20° without hitting the tripod leg. To adjust the mount in azimuth: 1. Locate the azimuth adjustment bolt on the flat portion of the tripod column (see figure 2-10). Loosen the two azimuth lock knobs located on the top of the tripod column. Turn the azimuth adjustment bolt with the 7/32" Allen wrench until the polar axis is pointing in the right direction. Tighten the azimuth lock knobs to hold the mount in place. The mount can be moved ± 7° in azimuth using these bolts. Azimuth Lock Knobs 2. 3. Altitude Adjustment Bolt 4. Helpful Hint: Located on the side of the equatorial mount head is a hole that serves as a convenient storage place for the polar alignment Allen wrench. This will help prevent you from misplacing the tool when polar aligning in the field. Keep in mind that adjusting the mount is done during the polar alignment process only. Once polar aligned, the mount must NOT be moved. Pointing the telescope is done by moving the mount in right ascension and declination, as described earlier in this manual. Once the appropriate adjustments have been made and you are aligned on the celestial pole, turn the clock drive on and the telescope will track. 12 Balancing The Mount in R.A. To eliminate undue stress on the mount, the telescope should be properly balanced around the polar axis. Proper balancing is crucial for accurate tracking. To balance the mount: 1. 2. 3. 4. 5. 6. Verify that the telescope securing knobs on the telescope mounting platform are tight. Loosen the R.A. clutch knobs and position the telescope off to one side of the mount. The counterweight bar will extend horizontally on the opposite side of the mount. Release the telescope -- GRADUALLY -- to see which way the telescope "rolls." Loosen the set screws on the side of the counterweight so it can be moved the length of the counterweight bar. Move the counterweight to a point where it balances the telescope (i.e., the telescope remains stationary when the R.A. clutch knobs are loose). Tighten the set screw on the counterweight to hold it in place. While the above instructions describe a perfect balance arrangement, there should be a SLIGHT imbalance to ensure the best possible tracking. When the scope is on the west side of the mount the counterweight should be slightly imbalanced to the counterweight bar side. And when the tube is on the east side of the mount there should be a slight imbalance toward the telescope side. This is done so that the worm gear is pushing against a slight load. The amount of the imbalance is very slight. When taking astrophotographs, this balance process can be done for the specific area at which the telescope is pointing to further optimize tracking accuracy. Figure 2-11 Balancing The Mount in DEC Although the telescope does not track in declination, the telescope should also be balanced in this axis to prevent any sudden motions when the DEC clutch knob is loose. To balance the telescope in DEC: 1. 2. 3. 4. Loosen the R.A. clutch knobs and rotate the telescope so that it is on one side of the mount (i.e., as described in the previous section on "Balancing the Mount in R.A."). Tighten the R.A. clutch knobs to hold the telescope in place. Loosen the DEC clutch knobs and rotate the telescope until the tube is parallel to the ground. Release the tube -- GRADUALLY -- to see which way it rotates around the declination axis. DO NOT LET GO OF THE TELESCOPE TUBE COMPLETELY! 13 5. Slightly loosen the knobs that holds the telescope to the mounting platform and slide the telescope either forward or backward until it remains stationary when the DEC clutch is loose. Do NOT let go of the telescope tube while the knob on the mounting platform is loose. Tighten the knobs on the telescope mounting platform to hold the telescope in place. 6. Once the telescope is balanced in declination, slide the dovetail bar safety clamp down the front of the telescope's slide bar until it touches the mounting platform and tighten the locking bolt. This not only acts as a safety in case the mounting platform knobs are loosened, but will also allow you to put the tube on the mount in the exact same position each time for perfect balance. Like R.A. balance, these are general balance instructions and will reduce undue stress on the mount. When taking astrophotographs, this balance process should be done for the specific area at which the telescope is pointing. Attaching the Motor Cables The CGE mount comes with two power cables to connect each drive motor to the electronics pier. To attach the motor cables: 1. Locate the Declination cable (the longer cable) and plug one end of the cable into the port on the electronics pier labeled DEC Port and plug the other end of the cable into the port located on the bottom of the declination motor (see figure2-12). 2. Locate the R.A. cable (the shorter cable) and plug one end of the cable into the port on the electronics pier labeled RA Port and plug the other end of the cable into the port located on the bottom of the right ascension motor (see figure2-12). Cable to DEC Motor Cable to R.A. Motor Powering the Telescope The CGE can be powered by the supplied car battery adapter or optional 12v AC. Use only the adapter supplied by Celestron. Using any other adapter may damage the electronics and will void your manufacturer's warranty. 1. Motor Ports Figure 2-12 To power the CGE with the car battery adapter (or 12v AC adapter), simply plug the round post into the 12v outlet on the electronic pier and plug the other end into your cars cigarette lighter outlet or portable power supply (see Optional Accessories). Note: to prevent the power cord from being accidentally pulled out, wrap the power cord around the strain relief located below the power switch. Turn on the power to the CGE by flipping the switch, located in the center of the pier, to the "On" position. 2. Transporting the CGE Because of the Celestron CGE telescope size and weight, you should ALWAYS remove the telescope from the mount when moving the telescope. To do so: 1. 2. 3. 4. 5. Take the telescope off of the mount and return it to its shipping box. Remove the counterweight from the counterweight bar. Remove the counterweight bar from the mount. Remove the finderscope from the optical tube. Take the equatorial mount off of the central column. 14 Figure 2-13 12v DC Power On/Off Switch Power Cord Strain Relief 6. 7. Remove the center leg brace from the tripod. Collapse the tripod legs inward, towards each other. The telescope is now broken down into enough pieces to be easily transported. Note: Before transporting the optical tube it is recommended that the two mirror locking screw located on the rear cell of the tube be locked down. Before tightening the screws, the primary mirror must be moved towards the rear cell of the tube. Rotate the focuser knob clockwise until you feel a slight resistance. The screws should now thread into the primary mirror mounting plate. When not in use, your CGE telescope can be left fully assembled and set up. However, all lens and eyepiece covers should be put back in place. This will reduce the amount of dust build-up on all optical surfaces and reduce the number of times you need to clean the instrument. You may want to return everything to its original shipping container and store it there. If this is the case, all optical surfaces should still be covered to prevent dust accumulation. 15 The CGE has a hand controller designed to give you instant access to all the functions the CGE has to offer. With automatic slewing to over 40,000 objects, and common sense menu descriptions, even a beginner can master its variety of features in just a few observing sessions. Below is a brief description of the individual components of the computerized hand controller: 1. 2. 3. Liquid Crystal Display (LCD) Window: Has a dual-line, 16 character display screen that is backlit for comfortable viewing of telescope information and scrolling text. Align: Instructs the CGE to use a selected star or object as an alignment position. Direction Keys: Allows complete control of the CGE in any direction. Use the direction keys to move the telescope to the initial alignment stars or for centering objects in the eyepiece. 1 7 2 8 3 9 4 10 5 11 6 12 Figure 3-1 The CGE Hand Control 16 4. Catalog Keys: The CGE has keys on the hand control to allow direct access to each of the catalogs in its database. The CGE contains the following catalogs in its database: Messier ­ Complete list of all Messier objects. NGC ­ Complete list of all the deep-sky objects in the Revised New General Catalog. Caldwell ­ A combination of the best NGC and IC objects. Planets - All 8 planets in our Solar System plus the Moon. Stars ­ A compiled list of the brightest stars from the SAO catalog. List ­ For quick access, all of the best and most popular objects in the CGE database have been broken down into lists based on their type and/or common name: Named Stars Named Objects Double Stars Variable Stars Asterisms CCD Objects IC Objects Abell Objects Constellation Common name listing of the brightest stars in the sky. Alphabetical listing of over 50 of the most popular deep sky objects. Numeric-alphabetical listing of the most visually stunning double, triple and quadruple stars in the sky. Select list of the brightest variable stars with the shortest period of changing magnitude. A unique list of some of the most recognizable star patterns in the sky. A custom list of many interesting galaxy pairs, trios and clusters that are well suited for CCD imaging with the CGE telescope. A complete list of all the Index Catalog deep-sky objects. A custom list of the Abell Catalog deep-sky galaxies. A complete list of all 88 constellations. Info: Displays coordinates and useful information about objects selected from the CGE database. Tour: Activates the tour mode, which seeks out all the best objects for the current date and time, and automatically slews the CGE to those objects. 7. Enter: Pressing Enter allows you to select any of the CGE functions and accept entered parameters. 8. Undo: Undo will take you out of the current menu and display the previous level of the menu path. Press Undo repeatedly to get back to a main menu or use it to erase data entered by mistake. 9. Menu: Displays the many setup and utilities functions such as tracking rate and user defined objects and many others. 10. Scroll Keys: Used to scroll up and down within any of the menu lists. A double-arrow will appear on the right side of the LCD when there are sub-menus below the displayed menu. Using these keys will scroll through those sub-menus. 11. Rate: Instantly changes the rate of speed of the motors when the direction buttons are pressed. 12. RS-232 Jack: Allows you to interface with a computer and control the CGE remotely. Hand Control Operation This section describes the basic hand control procedures needed to operate the CGE. These procedures are grouped into three categories: Alignment, Setup and Utilities. The alignment section deals with the initial telescope alignment as well as finding objects in the sky; the setup section discusses changing parameters such as tracking mode and tracking rate; finally, the last section reviews all of the utilities functions such as the calibrating your mount, PEC and backlash compensation. 5. 6. 17 Alignment Procedures In order for the CGE to accurately point to objects in the sky, it must first be aligned to two known positions (stars) in the sky. With this information, the telescope can create a model of the sky, which it uses to locate any object with known coordinates. There are many ways to align the CGE with the sky depending on what information the user is able to provide: Auto Two Star Alignment allows the user to select two stars and uses the entered time/location information to align the telescope; Auto One-Star Alignment involves the same process as Two-Star Align, however only uses one star position to align the telescope mount. Quick-Align will ask you to input all the same information as you would for the Auto Align procedure. However, instead of slewing to two alignment stars for centering and alignment, the telescope bypasses this step and simply models the sky based on the information given. Finally, Last Alignment restores your last saved star alignment and switch position. Last Alignment also serves as a good safeguard in case the telescope should lose power. Startup Procedure Before any of the described alignments are performed, the CGE needs to first index its switch position so that each axis has an equal amount of travel to move in either direction. It is a good idea to calibrate your mounts switch position after a successful alignment (see Calibrating the CGE Mount box on this page). Once the switch position has been set, the hand control will display the last entered date and time information stored in the hand control. Once the CGE is powered on: 1. Press ENTER begin the alignment process. 2. Press ENTER again to set the telescopes switch position. Press UNDO if you would like to manually move the telescope to a different switch position. This is useful if using your scope with additional equipment attached and its range of motion is limited. 3. After the telescope moves to its switch position, the hand control will display the last entered local time, date, time zone, longitude and latitude. · Use the Up/Down keys (10) to view the current parameters. · Press ENTER to accept the current parameters. · Press UNDO to enter current date and time information into the hand control. The following information will be displayed: Time - Enter the current local time for your area. You can enter either the local time (i.e. 08:00), or you can enter military time (i.e. 20:00 ). · Select PM or AM. If military time was entered, the hand control will bypass this step. · Choose between Standard time or Daylight Savings time. Use the Up and Down scroll buttons (10) to toggle between options. · Select the time zone that you are observing from. Again, use the Up and Down buttons Calibrating the CGE Mount In order to improve the pointing accuracy of your CGE telescope, the internal declination axis switch needs to be properly calibrated. This improves the pointing accuracy in two ways: First it measures and records the offset error when the declination switch is found at start-up. Second, it calculates and compensates for "cone" error inherent in all German equatorial mounts. Cone error is the inaccuracy that results from the optical tube not being perpendicular to the mounts declination axis. The mount should always be calibrated the first time it is used and only needs to be re-calibrated if the mount is used with a different optical tube or the optical tube is subjected to rough handling. Calibrating the mount is a very easy process and takes only a minute to do. To calibrate your CGE mount: · First, you must complete an Auto Two-Star Alignment as described in this section. However, you must take special notice to select two alignment stars that are on the same side of the Meridian (i.e. both in the western half of the sky or both in the eastern half of the sky). See Figure 3-2. · Once you have completed a successful alignment, slew to a known star that is on the other side of the Meridian from your two original alignment stars. · Press UNDO until CGE Ready is displayed. Press the MENU button on the hand control and select Calibrate Mount from the Utilities menu. · Scroll down to DEC Switch / Cone and press ENTER to begin the calibration. When the display asks you to center your calibration star, carefully center the star in the eyepiece making sure to use the Up and Right arrows keys to remove any of the backlash in the gears. Press ENTER to complete the calibration process. This calibration offset will be stored and used to improve the accuracy of future alignments. 18 · · (10) to scroll through the choices. Refer to Time Zone map in Appendix for more information. Date - Enter the month, day and year of your observing session. Finally, you must enter the longitude and latitude of the location of your observing site. Use the table in Appendix C to locate the closest longitude and latitude for your current observing location and enter those numbers when asked in the hand control, pressing ENTER after each entry. Remember to select "West" for longitudes in North America and "North" for latitudes in the North Hemisphere. For international cities, the correct hemisphere is indicated in the Appendix listings. 4. Select one of the four alignment methods as described below. Auto Two-Star Align Auto Two-Star Align allows the user to select two stars on which to align the telescope. To Auto Align your telescope: 1. Select Auto Two-Star from the alignment choices given. Based on the date and time information entered, the CGE will automatically select and display a bright star that is above the horizon. · Press ENTER to select this star as your first alignment star. · If for some reason the chosen star is not visible (perhaps behind a tree or building) press UNDO to have the hand control automatically select the next brightest star. · Or you can use the Up/Down keys to browse the entire Named Star list and select any one of over two hundred alignment stars. 2. Once the telescope is finished slewing to your first alignment star, the display will ask you to use the arrow buttons to align the selected star with the cross hairs in the center of the finderscope. When centered in the finder, press ENTER. 3. The display will then instruct you to center the star in the field of view of the eyepiece. When the star is centered, press ALIGN to accept this star as your first alignment star. 4. After the first alignment star has been entered the CGE will automatically select a second alignment star and have you repeat this procedure for that star. When the telescope has been aligned on both stars the display will read Alignment Successful, and you are now ready to find your first object. Figure 3-2 The Meridian is an imaginary line in the sky For the best possible pointing accuracy, always center the alignment that starts at the North celestial pole and stars using the up arrow button and the right arrow button. ends at the South celestial pole and passes Approaching the star from this direction when looking through the through the zenith. If you are facing South, the meridian starts from your Southern eyepiece will eliminate much of the backlash between the gears and horizon and passes directly overhead to the assure the most accurate alignment possible. North celestial pole. Observing Tip Auto One-Star Align Auto One-Star Alignment works much the same way as Auto Two-Star Align but uses only a single star in the sky for alignment. This method of alignment is not as accurate as the two-star alignment and is recommended only for telescopes that are permanently and accurately polar aligned. 19 Quick-Align Quick-Align uses all the date and time information entered at startup to align the telescope. However, instead of slewing to two alignment stars for centering and alignment, the CGE bypasses this step and simply models the sky based on the information given. This will allow you to roughly slew to the coordinates of bright objects like the moon and planets and gives the CGE the information needed to track objects in altazimuth in any part of the sky. Quick-Align is not meant to be used to accurately locate small or faint deep-sky objects or to track objects accurately for photography. To use Quick-Align, simply select Quick Align from the alignment options and press ENTER. The CGE will automatically use the entered date/time parameters to align itself with the sky and display Alignment Successful. Note: Once a Quick-Align has been done, you can use the Re-alignment feature (see next page) to improve your telescopes pointing accuracy. Last Alignment The CGE Last Alignment method will automatically recall the last saved mount switch positions, longitude and latitude along with the current date and time given from the real time clock, to continue using the alignment that was saved when the telescope was last powered down. This is a useful feature should your telescope accidentally lose power or be powered down. Note: Just like with Quick-Align, you can use the Re-alignment feature (see next page) to improve your telescopes pointing accuracy after using the Last Alignment method. To maintain a more accurate alignment over a series of observing sessions, use the Hibernate feature described later in this chapter. CGE Re-Alignment The CGE has a re-alignment feature which allows you to replace either of the two original alignment stars with a new star or celestial object. This can be useful in several situations: · · If you are observing over a period of a few hours, you may notice that your original two alignment stars have drifted towards the west considerably. (Remember that the stars are moving at a rate of 15º every hour). Aligning on a new star that is in the eastern part of the sky will improve your pointing accuracy, especially on objects in that part of the sky. If you have aligned your telescope using the Quick-Align method, you can use re-align to align to two actual objects in the sky. This will improve the pointing accuracy of your telescope without having to re-enter addition information. To replace an existing alignment star with a new alignment star: 1. 2. 3. 4. 5. 6. Select the desired star (or object) from the database and slew to it. Carefully center the object in the eyepiece. Once centered, press the UNDO button until you are at the main menu. With CGE Ready displayed, press the ALIGN key on the hand control. The display will then ask you which alignment star you want to replace. Use the UP and Down scroll keys to select the alignment star to be replaced. It is usually best to replace the star closest to the new object. This will space out your alignment stars across the sky. Press ALIGN to make the change. 20 Object Catalog Selecting an Object Now that the telescope is properly aligned, you can choose an object from any of the catalogs in the CGE's extensive database. The hand control has a key (4) designated for each of the catalogs in its database. There are two ways to select objects from the database: scrolling through the named object lists and entering object numbers. Pressing the LIST key on the hand control will access all objects in the database that have common names or types. Each list is broken down into the following categories: Named Stars, Named Object, Double Stars, Variable Stars, Asterisms and CCD Objects. Selecting any one of these catalogs will display a numeric-alphabetical listing of the objects under that list. Pressing the Up and Down keys (10) allows you to scroll through the catalog to the desired object. When scrolling through a long list of objects, holding down either the Up or Down key will allow you to scroll through the catalog more rapidly by only displaying every fifth catalog object. Pressing any of the other catalog keys (M, CALD, NGC, or STAR) will display a blinking cursor below the name of the catalog chosen. Use the numeric key pad to enter the number of any object within these standardized catalogs. For example, to find the Orion Nebula, press the "M" key and enter "042". Slewing to an Object Once the desired object is displayed on the hand control screen, choose from the following options: · · Helpful Hint Press the INFO Key. This will give you useful information about the selected object such as R.A. and declination, magnitude size and text information for many of the most popular objects. Press the ENTER Key. This will automatically slew the telescope to the coordinates of the object. Caution: Never slew the telescope when someone is looking into the eyepiece. The telescope can move at fast slew speeds and may hit an observer in the eye. Object information can be obtained without having to do a star alignment. After the telescope is powered on, pressing any of the catalog keys allows you to scroll through object lists or enter catalog numbers and view the information about the object as described above. Finding Planets The CGE can locate all 8 of our solar systems planets plus the Moon. However, the hand control will only display the solar system objects that are above the horizon (or within its filter limits). To locate the planets, press the PLANET key on the hand control. The hand control will display all solar system objects that are above the horizon: · · · Use the Up and Down keys to select the planet that you wish to observe. Press INFO to access information on the displayed planet. Press ENTER to slew to the displayed planet. 21 Tour Mode The CGE includes a tour feature which automatically allows the user to choose from a list of interesting objects based on the date and time in which you are observing. The automatic tour will display only those objects that are within your set filter limits (see Filter Limits in the Setup Procedures section of the manual). To activate the Tour mode, press the TOUR key (6) on the hand control. The CGE will display the best objects to observe that are currently in the sky. · · · To see information and data about the displayed object, press the INFO key. To slew to the object displayed, press ENTER. To see the next tour object, press the Up key. Constellation Tour In addition to the Tour Mode, the CGE telescope has a Constellation Tour that allows the user to take a tour of all the best objects in each of the 88 constellations. Selecting Constellation from the LIST menu will display all the constellation names that are above the user defined horizon (filter limits). Once a constellation is selected, you can choose from any of the database object catalogs to produce a list of all the available objects in that constellation. · · · To see information and data about the displayed object, press the INFO key. To slew to the object displayed, press ENTER. To see the next tour object, press the Up key. Direction Buttons The CGE has four direction buttons (3) in the center of the hand control which control the telescope's motion in altitude (up and down) and azimuth (left and right). The telescope can be controlled at nine different speed rates. Rate Button Pressing the RATE key (11) allows you to instantly change the speed rate of the motors from high speed slew rate to precise guiding rate or anywhere in between. Each rate corresponds to a number on the hand controller key pad. The number 9 is the fastest rate (4º per second, depending on power source) and is used for slewing between objects and locating alignment stars. The number 1 on the hand control is the slowest rate (.5x sidereal) and can be used for accurate centering of objects in the eyepiece and photographic guiding. To change the speed rate of the motors: · · Press the RATE key on the hand control. The LCD will display the current speed rate. Press the number on the hand control that corresponds to the desired speed. The number will appear in the upper-right corner of the LCD display to indicate that the rate has been changed. The hand control has a "double button" feature that allows you to instantly speed up the motors without having to choose a speed rate. To use this feature, simply press the arrow button that corresponds to the direction that you want to move the telescope. While holding that button down, press the opposite directional button. This will increase the slew rate to the maximum slew rate. When pressing the Up and Down arrow buttons in the slower slew rates (6 and lower) the motors will move the telescope in the opposite direction than the faster slew rates (7 thru 9). This is done so that an object will move in the appropriate direction when looking into the eyepiece (i.e. pressing the Up arrow button will move the star 22 up in the field of view of the eyepiece). However, if any of the slower slew rates (rate 6 and below) are used to center an object in the finderscope, you may need to press the opposite directional button to make the telescope move in the correct direction. 1 2 3 4 5 = = = = = .5x 1x (sidereal) 4x 8x 16x 6 7 8 9 = 64x = .5º / sec = 2º / sec = 4º / sec Nine available slew speeds Setup Procedures The CGE contains many user defined setup functions designed to give the user control over the telescope's many advanced features. All of the setup and utility features can be accessed by pressing the MENU key and scrolling through the options: Tracking Mode This allows you to change the way the telescope tracks depending on the type of mount being used to support the telescope. The CGE has three different tracking modes: EQ North Used to track the sky when the telescope is polar aligned in the Northern Hemisphere. Used to track the sky when the telescope is polar in the Southern Hemisphere. When using the telescope for terrestrial (land) observation, the tracking can be turned off so that the telescope never moves. EQ South Off Tracking Rate In addition to being able to move the telescope with the hand control buttons, the CGE will continually track a celestial object as it moves across the night sky. The tracking rate can be changed depending on what type of object is being observed: Sidereal This rate compensates for the rotation of the Earth by moving the telescope at the same rate as the rotation of the Earth, but in the opposite direction. When the telescope is polar aligned, this can be accomplished by moving the telescope in right ascension only. When mounted in Alt-Az mode, the telescope must make corrections in both R.A. and declination. Used for tracking the moon when observing the lunar landscape. Used for tracking the Sun when solar observing. Lunar Solar View Time-Site - Displays the current time and longitude/latitude downloaded from the optional CN-16 GPS receiver. It will also display other relevant time-site information like time zone, daylight saving and local 23 sidereal time. Local sidereal time (LST) is useful for knowing the right ascension of celestial objects that are located on the meridian at that time. View Time-Site will always display the last saved time and location entered while it is linking with the GPS. Once current information has been received, it will update the displayed information. If GPS is switched off, the hand control will only display the last saved time and location. User Defined Objects - The CGE can store up to 400 different user defined objects in its memory. The objects can be daytime land objects or an interesting celestial object that you discover that is not included in the regular database. There are several ways to save an object to memory depending on what type of object it is: To go to any of the user defined objects stored in the database, scroll down to either GoTo Sky Obj or Goto Land Obj and enter the number of the object you wish to select and press ENTER. CGE will automatically retrieve and display the coordinates before slewing to the object. The CGE stores celestial objects to its database by saving its right ascension and declination in the sky. This way the same object can be found each time the telescope is aligned. Once a desired object is centered in the eyepiece, simply scroll to the "Save Sky Obj" command and press ENTER. The display will ask you to enter a number between 1-200 to identify the object. Press ENTER again to save this object to the database. You can also store a specific set of coordinates for an object just by entering the R.A. and declination for that object. Scroll to the "Enter RA-DEC " command and press ENTER. The display will then ask you to enter first the R.A. and then the declination of the desired object. The CGE can also be used as a spotting scope on terrestrial objects. Fixed land objects can be stored by saving their altitude and azimuth relative to the location of the telescope at the time of observing. Since these objects are relative to the location of the telescope, they are only valid for that exact location. To save land objects, once again center the desired object in the eyepiece. Scroll down to the "Save Land Obj" command and press ENTER. The display will ask you to enter a number between 1-200 to identify the object. Press ENTER again to save this object to the database. GoTo Object: Save Sky Object: Enter R.A. - Dec: Save Land Object: To replace the contents of any of the user defined objects, simply save a new object using one of the existing identification numbers; CGE will replace the previous user defined object with the current one. Get RA/DEC - Displays the right ascension and declination for the current position of the telescope. Goto R.A/ Dec - Allows you to input a specific R.A. and declination and slew to it. Helpful Hint To store a set of coordinates (R.A./Dec) permanently into the CGE database, save it as a User Defined Object as described above. Identify Identify Mode will search any of the CGE database catalogs or lists and display the name and offset distances to the nearest matching objects. This feature can serve two purposes. First, it can be used to identify an unknown object in the field of view of your eyepiece. Additionally, Identify Mode can be used to find other celestial objects that are close to the objects you are currently observing. For example, if your telescope is pointed at the brightest star in the constellation Lyra, choosing Identify and then searching the Named Star catalog will no doubt return the star Vega as the star you are observing. However, by selecting Identify and searching by the 24 Named Object or Messier catalogs, the hand control will let you know that the Ring Nebula (M57) is approximately 6° from your current position. Searching the Double Star catalog will reveal that Epsilon Lyrae is only 1° away from Vega. To use the Identify feature: · · · Press the Menu button and select the Identify option. Use the Up/Down scroll keys to select the catalog that you would like to search. Press ENTER to begin the search. Note: Some of the databases contain thousands of objects, and can therefore take a minute or two to return the closest object. Precise GoTo The CGE has a precise goto function that can assist in finding extremely faint objects and centering objects closer to the center of the field of view for astrophotography and CCD imaging. Precise Goto automatically searches out the closest bright star to the desired object and asks the user to carefully center it in the eyepiece. The hand control then calculates the small difference between its goto position and its centered position. Using this offset, the telescope will then slew to the desired object with enhanced accuracy. To use Precise Goto: 1. · · 2. 3. 4. Press the MENU button and use the Up/Down keys to select Precise Goto. Choose Database to select the object that you want to observe from any of the database catalogs listed Choose RA/DEC to enter a set of celestial coordinates that you wish to slew to. Once the desired object is selected, the hand control will search out and display the closest bright star to your desired object. Press ENTER to slew to the bright alignment star. Use the direction buttons to carefully center the alignment star in the eyepiece. Press ENTER to slew to the desired object. SCOPE SETUP SETUP TIME-SITE ANTI-BACKLASH AZM POSITIVE AZM NEGATIVE ALT POSITIVE ALT NEGATIVE FILTER LIMITS ALTMAX IN LIST ALTMIN IN LIST DIRECTION BUTTONS AZM BUTTONS ALT BUTTONS GOTO APPROACH AZM APPROACH Scope Setup Features Setup Time-Site - Allows the user to customize the CGE display by changing time and location parameters (such as time zone and daylight savings). Anti-backlash ­ ­ All mechanical gears have a certain amount of backlash or play ALT APPROACH between the gears. This play is evident by how long it takes for a star to move in the AUTOGUIDE RATES eyepiece when the hand control arrow buttons are pressed (especially when changing directions). The CGE's anti-backlash features allows the user to compensate for backlash AZM RATE by inputting a value which quickly rewinds the motors just enough to eliminate the play ALT RATE between gears. The amount of compensation needed depends on the slewing rate MOUNT SETTINGS selected; the slower the slewing rate the longer it will take for the star to appear to move CONE VALUE in the eyepiece. There are two values for each axis, positive and negative. Positive is the DEC SWITCH amount of compensation applied when you press the button, in order to get the gears RA SWITCH moving quickly without a long pause. Negative is the amount of compensation applied when you release the button, winding the motors back in the other direction to resume tracking. You will need to experiment with different values (from 0-99); a value between 20 and 50 is usually best for most visual observing, whereas a higher value may be necessary for photographic guiding. To set the anti-backlash value, scroll down to the anti-backlash option and press ENTER. While viewing an object in the eyepiece, observe the responsiveness of each of the four arrow buttons. Note which directions you see a pause in the star movement after the button has been pressed. Working one axis at a time, adjust the backlash settings high enough to cause immediate movement without resulting in a pronounced jump when pressing or releasing the button. Now, enter the same values for both positive and negative directions. If you notice a jump when releasing the button, but setting the values lower results in a pause when pressing the 25 button, go with the higher value for positive, but use a lower value for negative. CGE will remember these values and use them each time it is turned on until they are changed. Filter Limits ­ When an alignment is complete, the CGE automatically knows which celestial objects are above the horizon. As a result, when scrolling through the database lists (or selecting the Tour function), the CGE hand control will display only those objects that are known to be above the horizon when you are observing. You can customize the object database by selecting altitude limits that are appropriate for your location and situation. For example, if you are observing from a mountainous location where the horizon is partially obscured, you can set your minimum altitude limit to read +20º. This will make sure that the hand control only displays objects that are higher in altitude than 20º. If you want to explore the entire object database, set the maximum altitude limit to 90º and the minimum limit to ­90º. This will display every object in the database lists regardless of whether it is visible in the sky from your location. Observing Tip! Direction Buttons ­The direction a star appears to move in the eyepiece changes depending on which side of the Meridian the telescope tube is on. This can create confusion especially when guiding on a star when doing astrophotography. To compensate for this, the direction of the drive control keys can be changed. To reverse the button logic of the hand control, press the MENU button and select Direction Buttons from the Utilities menu. Use the Up/Down arrow keys (10) to select either the azimuth (right ascension) or altitude (declination) button direction and press ENTER. Select either positive or negative for both axes and press ENTER to save. Setting the azimuth button direction to positive will move the telescope in the same direction that the telescope tracks (i.e. towards the west). Setting the altitude buttons to positive will move the telescope counterclockwise along the DEC axis. Direction Buttons will only change the eyepiece rates (rate 1-6) and will not affect the slew rates (rate 7-9). Goto Approach - lets the user define the direction that the telescope will approach when slewing to an object. This allows the user the ability to minimize the affects of backlash when slewing from object to object. Just like with Direction Buttons, setting GoTo Approach to positive will make the telescope approach an object from the same direction as tracking (west) for azimuth and counterclockwise in declination. Declination Goto approach will only apply while the telescope tube is on one side of the Meridian. Once the tube passes over to the other side of the Meridian, the Goto approach will need to be reversed. Helpful Hint! To change the Goto approach direction, simply choose Goto Approach from the Scope Setup menu, select either Altitude or Azimuth approach, choose positive or negative and press ENTER. In order to minimize the affect of gear backlash on pointing accuracy, the settings for Button Direction should ideally match the settings for GoTo Approach. By default, using the up and right direction buttons to center alignment stars will automatically eliminate much of the backlash in the gears. If you change the Goto approach of your telescope it is not necessary to change the Button Direction as well. Simply take notice of the direction the telescope moves when completing it final goto approach. If the telescope approaches its alignment star from the west (negative azimuth) and clockwise (negative altitude) than make sure that the buttons used to center the alignment stars also move the telescope in the same directions. Autoguide Rate ­ Allows the user to set an autoguide rate as a percentage of sidereal rate. This is helpful when calibrating your telescope to a CCD autoguider for long exposure photography. Mount Settings- Once the mount setting have been calibrated (see Utilities section below) the values are stored and displayed in the hand control. It is not recommended that the calibration values be changed, however each setting can be changed if necessary to improve the performance of the telescope. · Cone Value ­ This is the cone error value set when Utilities / Calibrate Mount / DEC Switch Cone is carried out. 26 · · DEC Switch - This is the declination switch error value set when Utilities / Calibrate Mount / DEC Switch - Cone is carried out. RA Switch - This is the R.A. switch error value set when Utilities / Calibrate Mount / R.A. Switch is carried out. Utility Features Scrolling through the MENU (9) options will also provide access to several advanced utility functions within the CGE such as; Mount Calibration, Periodic Error Correction, Hibernate as well as many others. Calibrate Mount - In order to optimize the performance and pointing accuracy of the CGE mount, the CGE has built-in calibration routines allowing it to compensate for mechanical variation inherent in every German equatorial mount. Each calibration is completely automatic and in most cases only needs to be performed once. It is highly recommended that you take a few minutes to go through the mount calibration procedures. · UTILITIES CALIBRATE MOUNT DEC SWITCH / CONE R.A. SWITCH GOTO MOVE TO SWITCH R.A. TO SWITCH DEC TO SWITCH HOME POSTION GOTO SET POLAR ALIGN PEC PLAYBACK RECORD LIGHT CONTROL FACTORY SETTING PRESS UNDO PRESS "0" VERSION GET ALT-AZ GOTO ATL-AZ HIBERNATE TURN ON/OFF RTC TURN ON/OFF GPS Dec Switch / Cone Calibration ­ this procedure simultaneously records the offset error when the declination switch is found at start-up and compensates for "cone" error due to slight misalignments of the optical tube and declination axis. For more information on calibrating the Dec switch and cone error, see the box called "Calibrating the CGE Mount" in the Startup Procedure section earlier in this chapter. R.A. Switch Calibration - this procedure records the offset error when the right ascension switch is found at start-up. Calibrating the R.A. switch will improve the accuracy of your initial star alignments when aligning the telescope. GoTo Calibration ­ Goto Calibration is a useful tool when attaching heavy visual or photographic accessories to the telescope. Goto Calibration calculates the amount of distance and time it takes for the mount to complete its final slow goto when slewing to an object. Changing the balance of the telescope can prolong the time it takes to complete the final slew. Goto Calibration takes into account any slight imbalances and changes the final goto distance to compensate. · · Move to Switch ­ Slews the telescope to locate either its R.A. or declination switches. Home Position ­ The telescopes "home" position is a user-definable position that is used to store the telescope when not in use. The home position is useful when storing the CGE telescope in a permanent observatory facility and especially when using the Hibernate feature to maintain a star align over many observing sessions. Polar Align- The CGE has a polar alignment function that will help you polar align your telescope for increased tracking precision and astrophotography. After performing an Auto Two-Star Alignment, the telescope will slew to where Polaris should be. By using the equatorial head to center Polaris in the eyepiece, the mount will then be pointed towards the actual North Celestial Pole. Once Polar Align is complete, you must re-align your telescope again using any of the alignment methods described earlier. To polar align the CGE mount in the Northern Hemisphere: 27 1. 2. With the telescope set up and roughly positioned towards Polaris, align the mount using the AutoTwoStar Alignment method. Select Polar Align from the Utilities menu and press Enter. Based on your current alignment, the CGE will slew to where it thinks Polaris should be. Use the equatorial head latitude and azimuth adjustments to place Polaris in the center of the eyepiece. Do not use the direction buttons to position Polaris. Once Polaris is centered in the eyepiece press ENTER; the polar axis should then be pointed towards the North Celestial Pole. Periodic Error Correction (PEC) - PEC is designed to improve photographic quality by reducing the amplitude of the worm gear errors and improving the tracking accuracy of the drive. This feature is for advanced astrophotography and is used when your telescope is accurately polar aligned. For more information on using PEC, see the section on "Celestial Photography". Light Control ­ This feature allows you to turn off both the red key pad light and LCD display for daytime use to conserve power and to help preserve your night vision. Factory Setting ­ Returns the CGE hand control to its original factory setting. Parameters such as backlash compensation values, initial date and time, longitude/latitude along with slew and filter limits will be reset. However, stored parameters such as PEC and user defined objects will remain saved even when Factory Settings is selected. The hand control will ask you to press the "0" key before returning to the factory default setting. Version - Selecting this option will allow you to see the current version number of the hand control, motor control and GPS software (if using optional CN-16 GPS accessory). The first set of numbers indicate the hand control software version. For the motor control, the hand control will display two sets of numbers; the first numbers are for azimuth and the second set are for altitude. On the second line of the LCD, the GPS and serial bus versions are displayed. Get Alt-Az - Displays the relative altitude and azimuth for the current position of the telescope. Goto Alt-Az - Allows you to enter a specific altitude and azimuth position and slew to it. Hibernate - Hibernate allows the CGE to be completely powered down and still retain its alignment when turned back on. This not only saves power, but is ideal for those that have their telescopes permanently mounted or leave their telescope in one location for long periods of time. To place your telescope in Hibernate mode: 1. Select Hibernate from the Utility Menu. 2. Move the telescope to a desire position and press ENTER. 3. Power off the telescope. Remember to never move your telescope manually while in Hibernate mode. Once the telescope is powered on again the display will read Wake Up. After pressing Enter you have the option of scrolling through the time/site information to confirm the current setting. Press ENTER to wake up the telescope. Pressing UNDO at the Wake Up screen allows you to explore many of the features of the hand control without waking the telescope up from hibernate mode. To wake up the telescope after UNDO has been pressed, select Hibernate from the Utility menu and press ENTER. Do not use the direction buttons to move the telescope while in hibernate mode. Helpful Hint Turn On/Off RTC - Allows you to turn off the telescopes internal real time clock. When aligning the telescope using AutoAlign, the CGE still receives time information from the RTC. If you want to use the CGE database to find the coordinates of a celestial object for a future or past dates you would need to turn the RTC off in order to manually enter a time other than the present. 28 Turn On/Off GPS - If using your CGE telescope with the optional CN-16 GPS accessory (see Optional Accessories section of the manual), you will need to turn the GPS on the first time you use the accessory. Additionally, just like with the real time clock you will need to turn the GPS module off in order to enter dates and location other than the current information downloaded by the GPS. 29 CGE Ready MENU TRACKING MODE EQ NORTH EQ SOUTH OFF RATE SIDEREAL SOLAR LUNAR VIEW TIME-SITE SCOPE SETUP SETUP TIME-SITE ANTI-BACKLASH FILTER LIMITS DIRECTION BUTTONS GOTO APPROACH AUTOGUIDE RATE MOUNT SETTINGS UTILITIES CALIBRATE MOUNT MOVE TO SWITCH HOME POSITION POLAR ALIGN PEC LIGHT CONTROL FACTORY SETTING VERSION GET ALT-AZ GOTO ALT-AZ HIBERNATE TURN ON/OFF RTC TURN ON/OFF GPS USER OBJECTS GOTO SKY OBJ SAVE SKY OBJ ENTER RA & DEC SAVE LAND OBJ GOTO LAND OBJ GET RA-DEC GOTO RA-DEC IDENTIFY SELECT CATALOG PRECISE GOTO GOTO TYPE ALIGNMENT START-UP PROCUDURE SET SWITCH POSITION ENTER TIME DLS/ST TIME ZONE ENTER DATE- MM/DD/YY ENTER LONG/LAT AUTO TWO-STAR ALIGNMENT SELECT STAR 1 CENTER STAR 1 SELECT STAR 2 CENTER STAR 2 LIST NAMED STAR NAMED OBJECT ASTERISM TOUR VARIABLE STAR DOUBLE STAR CCD OBJECTS ABELL IC CATALOG CALDWELL MESSIER NGC SAO SOLAR SYSTEM CONSTELLATION AUTO ONE-STAR ALIGNMENT SELECT STAR 1 CENTER STAR 1 QUICK-ALIGN LAST ALIGNMENT CGE Menu Tree: The following figure is a menu tree showing the sub-menus associated with the primary command functions 30 A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused. Some telescopes, known as refractors, use lenses. Other telescopes, known as reflectors, use mirrors. The Schmidt-Cassegrain optical system (or Schmidt-Cass for short) uses a combination of mirrors and lenses and is referred to as a compound or catadioptric telescope. This unique design offers large-diameter optics while maintaining very short tube lengths, making them extremely portable. The Schmidt-Cassegrain system consists of a zero power corrector plate, a spherical primary mirror, and a secondary mirror. Once light rays enter the optical system, they travel the length of the optical tube three times. The optics of the CGE have Starbright coatings - enhanced multi-layer coatings on the primary and secondary mirrors for increased reflectivity and a fully coated corrector for the finest anti-reflection characteristics. Inside the optical tube, a black tube extends out from the center hole in the primary mirror. This is the primary baffle tube and it prevents stray light from passing through to the eyepiece or camera. Figure 4-1 A cutaway view of the light path of the Schmidt-Cassegrain optical design Image Orientation The image orientation changes depending on how the eyepiece is inserted into the telescope. When using the star diagonal, the image is right-side-up, but reversed from left-to-right (i.e., mirror image). If inserting the eyepiece directly into the visual back (i.e., without the star diagonal), the image is upside-down and reversed from left-to-right (i.e., inverted). This is normal for the Schmidt-Cassegrain design. Actual image orientation as seen with the unaided eye Reversed from left to right, as viewed with a Star Diagonal Figure 4-2 Inverted image, as viewed with the eyepiece directly in telescope 31 Focusing The CGE's focusing mechanism controls the primary mirror which is mounted on a ring that slides back and forth on the primary baffle tube. The focusing knob, which moves the primary mirror, is on the rear cell of the telescope just below the star diagonal and eyepiece. Turn the focusing knob until the image is sharp. If the knob will not turn, it has reached the end of its travel on the focusing mechanism. Turn the knob in the opposite direction until the image is sharp. Once an image is in focus, turn the knob clockwise to focus on a closer object and counterclockwise for a more distant object. A single turn of the focusing knob moves the primary mirror only slightly. Therefore, it will take many turns (about 30) to go from close focus (approximately 60 feet) to infinity. For astronomical viewing, out of focus star images are very diffuse, making them difficult to see. If you turn the focus knob too quickly, you can go right through focus without seeing the image. To avoid this problem, your first astronomical target should be a bright object (like the Moon or a planet) so that the image is visible even when out of focus. Critical focusing is best accomplished when the focusing knob is turned in such a manner that the mirror moves against the pull of gravity. In doing so, any mirror shift is minimized. For astronomical observing, both visually and photographically, this is done by turning the focus knob counterclockwise. Figure 4-3 The emblem on the end of the focus knob shows the correct rotational direction for focusing the CGE. NOTE: Before turning the focus knob, remember to lossen to two mirror locking knobs located on the rear cell of the telescope. These knobs connect a screw to the primary mirror mounting plate and prevent the mirror from moving when locked down. These screws should be locked down when transporting the telescope. Calculating Magnification You can change the power of your telescope just by changing the eyepiece (ocular). To determine the magnification of your telescope, simply divide the focal length of the telescope by the focal length of the eyepiece used. In equation format, the formula looks like this: Focal Length of Telescope (mm) Magnification = Focal Length of Eyepiece (mm) Let's say, for example, you are using the 40mm Plossl eyepiece. To determine the magnification you simply divide the focal length of your telescope (the CGE1100 for example has a focal length of 2800mm) by the focal length of the eyepiece, 40mm. Dividing 2800 by 40 yields a magnification of 70 power. Although the power is variable, each instrument under average skies has a limit to the highest useful magnification. The general rule is that 60 power can be used for every inch of aperture. For example, the CGE1100 is 11 inches in diameter. Multiplying 11 by 60 gives a maximum useful magnification of 660 power. Although this is the maximum useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 220 to 385 times for the CGE1100 telescope. Determining Field of View Determining the field of view is important if you want to get an idea of the angular size of the object you are observing. To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer) by the magnification. In equation format, the formula looks like this: Apparent Field of Eyepiece True Field = Magnification As you can see, before determining the field of view, you must calculate the magnification. Using the example in the previous section, we can determine the field of view using the same 40mm eyepiece. The 40mm Plossl eyepiece has an apparent field of view of 46°. Divide the 46° by the magnification, which is 70 power. This yields an actual field of .66°, or two-thirds of a full degree. 32 To convert degrees to feet at 1,000 yards, which is more useful for terrestrial observing, simply multiply by 52.5. Continuing with our example, multiply the angular field .66° by 52.5. This produces a linear field width of 34.7 feet at a distance of one thousand yards. The apparent field of each eyepiece that Celestron manufactures is found in the Celestron Accessory Catalog (#93685). General Observing Hints When working with any optical instrument, there are a few things to remember to ensure you get the best possible image. · · · · Never look through window glass. Glass found in household windows is optically imperfect, and as a result, may vary in thickness from one part of a window to the next. This inconsistency can and will affect the ability to focus your telescope. In most cases you will not be able to achieve a truly sharp image, while in some cases, you may actually see a double image. Never look across or over objects that are producing heat waves. This includes asphalt parking lots on hot summer days or building rooftops. Hazy skies, fog, and mist can also make it difficult to focus when viewing terrestrially. The amount of detail seen under these conditions is greatly reduced. Also, when photographing under these conditions, the processed film may come out a little grainier than normal with lower contrast and underexposed. If you wear corrective lenses (specifically glasses), you may want to remove them when observing with an eyepiece attached to the telescope. When using a camera, however, you should always wear corrective lenses to ensure the sharpest possible focus. If you have astigmatism, corrective lenses must be worn at all times. 33 Up to this point, this manual covered the assembly and basic operation of your CGE telescope. However, to understand your telescope more thoroughly, you need to know a little about the night sky. This section deals with observational astronomy in general and includes information on the night sky and polar alignment. The Celestial Coordinate System To help find objects in the sky, astronomers use a celestial coordinate system that is similar to our geographical coordinate system here on Earth. The celestial coordinate system has poles, lines of longitude and latitude, and an equator. For the most part, these remain fixed against the background stars. The celestial equator runs 360 degrees around the Earth and separates the northern celestial hemisphere from the southern. Like the Earth's equator, it bears a reading of zero degrees. On Earth this would be latitude. However, in the sky this is referred to as declination, or DEC for short. Lines of declination are named for their angular distance above and below the celestial equator. The lines are broken down into degrees, minutes of arc, and seconds of arc. Declination readings south of the equator carry a minus sign (-) in front of the coordinate and those north of the celestial equator are either blank (i.e., no designation) or preceded by a plus sign (+). The celestial equivalent of longitude is called Right Ascension, or R.A. for short. Like the Earth's lines of longitude, they run from pole to pole and are evenly spaced 15 degrees apart. Although the longitude lines are separated by an angular distance, they are also a measure of time. Each line of longitude is one hour apart from the next. Since the Earth rotates once every 24 hours, there are 24 lines total. As a result, the R.A. coordinates are marked off in units of time. It begins with an arbitrary point in the constellation of Pisces designated as 0 hours, 0 minutes, 0 seconds. All other points are designated by how far (i.e., how long) they lag behind this coordinate after it passes overhead moving toward the west. Figure 5-1 The celestial sphere seen from the outside showing R.A. and DEC. 34 Motion of the Stars The daily motion of the Sun across the sky is familiar to even the most casual observer. This daily trek is not the Sun moving as early astronomers thought, but the result of the Earth's rotation. The Earth's rotation also causes the stars to do the same, scribing out a large circle as the Earth completes one rotation. The size of the circular path a star follows depends on where it is in the sky. Stars near the celestial equator form the largest circles rising in the east and setting in the west. Moving toward the north celestial pole, the point around which the stars in the northern hemisphere appear to rotate, these circles become smaller. Stars in the mid-celestial latitudes rise in the northeast and set in the northwest. Stars at high celestial latitudes are always above the horizon, and are said to be circumpolar because they never rise and never set. You will never see the stars complete one circle because the sunlight during the day washes out the starlight. However, part of this circular motion of stars in this region of the sky can be seen by setting up a camera on a tripod and opening the shutter for a couple hours. The processed film will reveal semicircles that revolve around the pole. (This description of stellar motions also applies to the southern hemisphere except all stars south of the celestial equator move around the south celestial pole.) Figure 5-2 All stars appear to rotate around the celestial poles. However, the appearance of this motion varies depending on where you are looking in the sky. Near the north celestial pole the stars scribe out recognizable circles centered on the pole (1). Stars near the celestial equator also follow circular paths around the pole. But, the complete path is interrupted by the horizon. These appear to rise in the east and set in the west (2). Looking toward the opposite pole, stars curve or arc in the opposite direction scribing a circle around the opposite pole (3). 35 Latitude Scales The easiest way to polar align a telescope is with a latitude scale. Unlike other methods that require you to find the celestial pole by identifying certain stars near it, this method works off of a known constant to determine how high the polar axis should be pointed. The Celestron CGE1100 mount can be adjusted from 13 to 65 degrees (see figure 5-3). The constant, mentioned above, is a relationship between your latitude and the angular distance the celestial pole is above the northern (or southern) horizon; The angular distance from the northern horizon to the north celestial pole is always equal to your latitude. To illustrate this, imagine that you are standing on the north pole, latitude +90°. The north celestial pole, which has a declination of +90°, would be directly overhead (i.e., 90 above the horizon). Now, let's say that you move one degree south -- your latitude is now +89° and the celestial pole is no longer directly overhead. It has moved one degree closer Latitude Scale Figure 5-3 toward the northern horizon. This means the pole is now 89° above the northern horizon. If you move one degree further south, the same thing happens again. You would have to travel 70 miles north or south to change your latitude by one degree. As you can see from this example, the distance from the northern horizon to the celestial pole is always equal to your latitude. If you are observing from Los Angeles, which has a latitude of 34°, then the celestial pole is 34° above the northern horizon. All a latitude scale does then is to point the polar axis of the telescope at the right elevation above the northern (or southern) horizon. To align your telescope: 1. 2. Make sure the polar axis of the mount is pointing due north. Use a landmark that you know faces north. Level the tripod. There is a bubble level built into the mount for this purpose. NOTE: Leveling the tripod is only necessary if using this method of polar alignment. Perfect polar alignment is still possible using other methods described later in this manual without leveling the tripod. 3. Adjust the mount in altitude until the latitude indicator points to your latitude. Moving the mount affects the angle the polar axis is pointing. For specific information on adjusting the equatorial mount, please see the section "Adjusting the Mount." This method can be done in daylight, thus eliminating the need to fumble around in the dark. Although this method does NOT put you directly on the pole, it will limit the number of corrections you will make when tracking an object. It will also be accurate enough for short exposure prime focus planetary photography (a couple of seconds) and short exposure piggyback astrophotography (a couple of minutes). Pointing at Polaris This method utilizes Polaris as a guidepost to the celestial pole. Since Polaris is less than a degree from the celestial pole, you can simply point the polar axis of your telescope at Polaris. Although this is by no means perfect alignment, it does get you within one degree. Unlike the previous method, this must be done in the dark when Polaris is visible. 1. Set the telescope up so that the polar axis is pointing north. 36 2. Loosen the DEC clutch knob and move the telescope so that the tube is parallel to the polar axis. When this is done, the declination setting circle will read +90°. If the declination setting circle is not aligned, move the telescope so that the tube is parallel to the polar axis. Adjust the mount in altitude and/or azimuth until Polaris is in the field of view of the finder. Center Polaris in the field of the telescope using the fine adjustment controls on the mount. Remember, while Polar aligning, do NOT move the telescope in R.A. or DEC. You do not want to move the telescope itself, but the polar axis. The telescope is used simply to see where the polar axis is pointing. Like the previous method, this gets you close to the pole but not directly on it. The following methods help improve your accuracy for more serious observations and photography. Finding the North Celestial Pole In each hemisphere, there is a point in the sky around which all the other stars appear to rotate. These points are called the celestial poles and are named for the hemisphere in which they reside. For example, in the northern hemisphere all stars move around the north celestial pole. When the telescope's polar axis is pointed at the celestial pole, it is parallel to the Earth's rotational axis. Many methods of polar alignment require that you know how to find the celestial pole by identifying stars in the area. For those in the northern hemisphere, finding the celestial pole is not too difficult. Fortunately, we have a naked eye star less than a degree away. This star, Polaris, is the end star in the handle of the Little Dipper. Since the Little Dipper (technically called Ursa Minor) is not one of the brightest constellations in the sky, it may be difficult to locate from urban areas. If this is the case, use the two end stars in the bowl of the Big Dipper (the pointer stars). Draw an imaginary line through them toward the Little Dipper. They point to Polaris (see Figure 5-5). The position of the Big Dipper changes during the year and throughout the course of the night (see Figure 5-4). When the Big Dipper is low in the sky (i.e., near the horizon), it may be difficult to locate. During these times, look for Cassiopeia (see Figure 5-5). Observers in the southern hemisphere are not as fortunate as those in the northern hemisphere. The stars around the south celestial pole are not nearly as bright as those around the north. The closest star that is relatively bright is Sigma Octantis. This star is just within naked eye limit (magnitude 5.5) and lies about 59 arc minutes from the pole. 3. 4. Definition The north celestial pole is the point in the northern hemisphere around which all stars appear to rotate. The counterpart in the southern hemisphere is referred to as the south celestial pole. Figure 5-4 The position of the Big Dipper changes throughout the year and the night. Figure 5-5 The two stars in the front of the bowl of the Big Dipper point to Polaris which is less than one degree from the true (north) celestial pole. Cassiopeia, the "W" shaped constellation, is on the opposite side of the pole from the Big Dipper. The North Celestial Pole (N.C.P.) is marked by the "+" sign. 37 Declination Drift Method of Polar Alignment This method of polar alignment allows you to get the most accurate alignment on the celestial pole and is required if you want to do long exposure deep-sky astrophotography through the telescope. The declination drift method requires that you monitor the drift of selected stars. The drift of each star tells you how far away the polar axis is pointing from the true celestial pole and in what direction. Although declination drift is simple and straight-forward, it requires a great deal of time and patience to complete when first attempted. The declination drift method should be done after any one of the previously mentioned methods has been completed. To perform the declination drift method you need to choose two bright stars. One should be near the eastern horizon and one due south near the meridian. Both stars should be near the celestial equator (i.e., 0° declination). You will monitor the drift of each star one at a time and in declination only. While monitoring a star on the meridian, any misalignment in the east-west direction is revealed. While monitoring a star near the east/west horizon, any misalignment in the north-south direction is revealed. It is helpful to have an illuminated reticle eyepiece to help you recognize any drift. For very close alignment, a Barlow lens is also recommended since it increases the magnification and reveals any drift faster. When looking due south, insert the diagonal so the eyepiece points straight up. Insert the cross hair eyepiece and align the cross hairs so that one is parallel to the declination axis and the other is parallel to the right ascension axis. Move your telescope manually in R.A. and DEC to check parallelism. First, choose your star near where the celestial equator and the meridian meet. The star should be approximately within 1/2 an hour of the meridian and within five degrees of the celestial equator. Center the star in the field of your telescope and monitor the drift in declination. · · If the star drifts south, the polar axis is too far east. If the star drifts north, the polar axis is too far west. Make the appropriate adjustments to the polar axis to eliminate any drift. Once you have eliminated all the drift, move to the star near the eastern horizon. The star should be 20 degrees above the horizon and within five degrees of the celestial equator. · · If the star drifts south, the polar axis is too low. If the star drifts north, the polar axis is too high. Again, make the appropriate adjustments to the polar axis to eliminate any drift. Unfortunately, the latter adjustments interact with the prior adjustments ever so slightly. So, repeat the process again to improve the accuracy checking both axes for minimal drift. Once the drift has been eliminated, the telescope is very accurately aligned. You can now do prime focus deep-sky astrophotography for long periods. NOTE: If the eastern horizon is blocked, you may choose a star near the western horizon, but you must reverse the polar high/low error directions. Also, if using this method in the southern hemisphere, the direction of drift is reversed for both R.A. and DEC. 38 With your telescope set up, you are ready to use it for observing. This section covers visual observing hints for both solar system and deep sky objects as well as general observing conditions which will affect your ability to observe. Observing the Moon Often, it is tempting to look at the Moon when it is full. At this time, the face we see is fully illuminated and its light can be overpowering. In addition, little or no contrast can be seen during this phase. One of the best times to observe the Moon is during its partial phases (around the time of first or third quarter). Long shadows reveal a great amount of detail on the lunar surface. At low power you will be able to see most of the lunar disk at one time. The optional Reducer/Corrector lens allows for breath-taking views of the entire lunar disk when used with a low power eyepiece. Change to higher power (magnification) to focus in on a smaller area. Choose the lunar tracking rate from the CGE's MENU tracking rate options to keep the moon centered in the eyepiece even at high magnifications. Lunar Observing Hints To increase contrast and bring out detail on the lunar surface, use filters. A yellow filter works well at improving contrast while a neutral density or polarizing filter will reduce overall surface brightness and glare. Observing the Planets Other fascinating targets include the five naked eye planets. You can see Venus go through its lunar-like phases. Mars can reveal a host of surface detail and one, if not both, of its polar caps. You will be able to see the cloud belts of Jupiter and the great Red Spot (if it is visible at the time you are observing). In addition, you will also be able to see the moons of Jupiter as they orbit the giant planet. Saturn, with its beautiful rings, is easily visible at moderate power. Planetary Observing Hints · Remember that atmospheric conditions are usually the limiting factor on how much planetary detail will be visible. So, avoid observing the planets when they are low on the horizon or when they are directly over a source of radiating heat, such as a rooftop or chimney. See the "Seeing Conditions" section later in this section. To increase contrast and bring out detail on the planetary surface, try using Celestron eyepiece filters. · 39 Observing the Sun Although overlooked by many amateur astronomers, solar observation is both rewarding and fun. However, because the Sun is so bright, special precautions must be taken when observing our star so as not to damage your eyes or your telescope. Never project an image of the Sun through the telescope. Because of the folded optical design, tremendous heat buildup will result inside the optical tube. This can damage the telescope and/or any accessories attached to the telescope. For safe solar viewing, use a solar filter that reduces the intensity of the Sun's light, making it safe to view. With a filter you can see sunspots as they move across the solar disk and faculae, which are bright patches seen near the Sun's edge. Solar Observing Hints · · The best time to observe the Sun is in the early morning or late afternoon when the air is cooler. To center the Sun without looking into the eyepiece, watch the shadow of the telescope tube until it forms a circular shadow. To ensure accurate tracking, be sure to select the solar tracking rate. · Observing Deep Sky Objects Deep-sky objects are simply those objects outside the boundaries of our solar system. They include star clusters, planetary nebulae, diffuse nebulae, double stars and other galaxies outside our own Milky Way. Most deep-sky objects have a large angular size. Therefore, low-to-moderate power is all you need to see them. Visually, they are too faint to reveal any of the color seen in long exposure photographs. Instead, they appear black and white. And, because of their low surface brightness, they should be observed from a dark-sky location. Light pollution around large urban areas washes out most nebulae making them difficult, if not impossible, to observe. Light Pollution Reduction filters help reduce the background sky brightness, thus increasing contrast. Seeing Conditions Viewing conditions affect what you can see through your telescope during an observing session. Conditions include transparency, sky illumination, and seeing. Understanding viewing conditions and the effect they have on observing will help you get the most out of your telescope. Transparency Transparency is the clarity of the atmosphere which is affected by clouds, moisture, and other airborne particles. Thick cumulus clouds are completely opaque while cirrus can be thin, allowing the light from the brightest stars through. Hazy skies absorb more light than clear skies making fainter objects harder to see and reducing contrast on brighter objects. Aerosols ejected into the upper atmosphere from volcanic eruptions also affect transparency. Ideal conditions are when the night sky is inky black. Sky Illumination General sky brightening caused by the Moon, aurorae, natural airglow, and light pollution greatly affect transparency. While not a problem for the brighter stars and planets, bright skies reduce the contrast of extended nebulae making them difficult, if not impossible, to see. To maximize your observing, limit deep sky viewing to moonless nights far from the light polluted skies found around major urban areas. LPR filters enhance deep sky viewing from light polluted areas by blocking unwanted light while transmitting light from certain deep sky objects. You can, on the other hand, observe planets and stars from light polluted areas or when the Moon is out. 40 Seeing Seeing conditions refers to the stability of the atmosphere and directly affects the amount of fine detail seen in extended objects. The air in our atmosphere acts as a lens which bends and distorts incoming light rays. The amount of bending depends on air density. Varying temperature layers have different densities and, therefore, bend light differently. Light rays from the same object arrive slightly displaced creating an imperfect or smeared image. These atmospheric disturbances vary from time-to-time and place-to-place. The size of the air parcels compared to your aperture determines the "seeing" quality. Under good seeing conditions, fine detail is visible on the brighter planets like Jupiter and Mars, and stars are pinpoint images. Under poor seeing conditions, images are blurred and stars appear as blobs. The conditions described here apply to both visual and photographic observations. Figure 6-1 Seeing conditions directly affect image quality. These drawings represent a point source (i.e., star) under bad seeing conditions (left) to excellent conditions (right). Most often, seeing conditions produce images that lie some where between these two extremes. 41 After looking at the night sky for a while you may want to try photographing it. Several forms of celestial photography are possible with your telescope, including short exposure prime focus, eyepiece projection, long exposure deep sky, terrestrial and even CCD imaging. Each of these is discussed in moderate detail with enough information to get you started. Topics include the accessories required and some simple techniques. More information is available in some of the publications listed at the end of this manual. In addition to the specific accessories required for each type of celestial photography, there is the need for a camera but not just any camera. The camera does not have to have many of the features offered on today's state-of-the-art equipment. For example, you don't need auto focus capability or mirror lock up. Here are the mandatory features a camera needs for celestial photography. First, a "B" setting which allows for time exposures. This excludes point and shoot cameras and limits the selection to SLR cameras, the most common type of 35mm camera on the market today. Second, the "B" or manual setting should NOT run off the battery. Many new electronic cameras use the battery to keep the shutter open during time exposures. Once the batteries are drained, usually after a few minutes, the shutter closes, whether you were finished with the exposure or not. Look for a camera that has a manual shutter when operating in the time exposure mode. Olympus, Nikon, Minolta, Pentax, Canon and others have made such camera bodies. The camera must have interchangeable lenses so you can attach it to the telescope and so you can use a variety of lenses for piggyback photography. If you can't find a new camera, you can purchase a used camera body that is not 100-percent functional. The light meter, for example, does not have to be operational since you will be determining the exposure length manually. You also need a cable release with a locking function to hold the shutter open while you do other things. Mechanical and air release models are available. Short Exposure Prime Focus Photography Short exposure prime focus photography is the best way to begin recording celestial objects. It is done with the camera attached to the telescope without an eyepiece or camera lens in place. To attach your camera you need the Celestron TAdapter (#93633-A) and a T-Ring for your specific camera (i.e., Minolta, Nikon, Pentax, etc.). The T-Ring replaces the 35mm SLR camera's normal lens. Prime focus photography allows you to capture the majority of the lunar disk or solar disk. To attach your camera to your telescope. 1. 2. 3. 4. Remove all visual accessories. Thread the T-Ring onto the T-Adapter. Mount your camera body onto the T-Ring the same as you would any other lens. Thread the T-Adapter onto the back of the telescope while holding the camera in the desired orientation (either vertical or horizontal). With your camera attached to the telescope, you are ready for prime focus photography. Start with an easy object like the Moon. Here's how to do it: 1. Load your camera with film that has a moderate-to-fast speed (i.e., ISO rating). Faster films are more desirable when the Moon is a crescent. When the Moon is near full, and at its brightest, slower films are more desirable. Here are some film recommendations: T-Max 100 · 42 · · · · 2. 3. 4. 5. 6. T-Max 400 Any 100 to 400 ISO color slide film Fuji Super HG 400 Ektar 25 or 100 Center the Moon in the field of your CGE telescope. Focus the telescope by turning the focus knob until the image is sharp. Set the shutter speed to the appropriate setting (see table below). Trip the shutter using a cable release. Advance the film and repeat the process. Lunar Phase Crescent Quarter Full ISO 50 1/2 1/15 1/30 ISO 100 1/4 1/30 1/60 ISO 200 1/8 1/60 1/125 ISO 400 1/15 1/125 1/250 Table 7-1 Above is a listing of recommended exposure times when photographing the Moon at the prime focus of your CGE telescope. The exposure times listed in table 7-1 should be used as a starting point. Always make exposures that are longer and shorter than the recommended time. Also, take a few photos at each shutter speed. This will ensure that you will get a good photo. · · If using black and white film, try a yellow filter to reduce the light intensity and to increase contrast. Keep accurate records of your exposures. This information is useful if you want to repeat your results or if you want to submit some of your photos to various astronomy magazines for possible publication! This technique is also used for photographing the Sun with the proper solar filter. · Eyepiece Projection This form of celestial photography is designed for objects with small angular sizes, primarily the Moon and planets. Planets, although physically quite large, appear small in angular size because of their great distances. Moderate to high magnification is, therefore, required to make the image large enough to see any detail. Unfortunately, the camera/telescope combination alone does not provide enough magnification to produce a usable image size on film. In order to get the image large enough, you must attach your camera to the telescope with the eyepiece in place. To do so, you need two additional accessories; a deluxe tele-extender (#93643), which attaches to the visual back, and a T-ring for your particular camera make (i.e., Minolta, Nikon, Pentax, etc.). Because of the high magnifications during eyepiece projection, the field of view is quite small which makes it difficult to find and center objects. To make the job a little easier, align the finder as accurately as possible. This allows you to get the object in the telescope's field based on the finder's view alone. Another problem introduced by the high magnification is vibration. Simply tripping the shutter even with a cable release produces enough vibration to smear the image. To get around this, use the camera's self-timer if the exposure time is less than one second a common occurrence when photographing the Moon. For exposures over one second, use the "hat trick." This technique incorporates a hand-held black card placed over the aperture of the telescope to Figure 7-1 - Accessories for Projection Photography 43 act as a shutter. The card prevents light from entering the telescope while the shutter is released. Once the shutter has been released and the vibration has diminished (a few seconds), move the black card out of the way to expose the film. After the exposure is complete, place the card over the front of the telescope and close the shutter. Advance the film and you're ready for your next shot. Keep in mind that the card should be held a few inches in front of the telescope, and not touching it. It is easier if you use two people for this process; one to release the camera shutter and one to hold the card. Here's the process for making the exposure. 1. 2. 3. 4. 5. 6. 7. 8. Find and center the desired target in the viewfinder of your camera. Turn the focus knob until the image is as sharp as possible. Place the black card over the front of the telescope. Release the shutter using a cable release. Wait for the vibration caused by releasing the shutter to diminish. Also, wait for a moment of good seeing. Remove the black card from in front of the telescope for the duration of the exposure (see accompanying table). Replace the black card over the front of the telescope. Close the camera's shutter. Advance the film and you are ready for your next exposure. Don't forget to take photos of varying duration and keep accurate records of what you have done. Record the date, telescope, exposure duration, eyepiece, f/ratio, film, and some comments on the seeing conditions. The following table lists exposures for eyepiece projection with a 10mm eyepiece. All exposure times are listed in seconds or fractions of a second. Planet Moon Mercury Venus Mars Jupiter Saturn ISO 50 4 16 1/2 16 8 16 ISO 100 2 8 1/4 8 4 8 ISO 200 1 4 1/8 4 2 4 ISO 400 1/2 2 1/15 2 1 2 Table 7-2 Recommended exposure time for photographing planets. The exposure times listed here should be used as a starting point. Always make exposures that are longer and shorter than the recommended time. Also, take a few photos at each shutter speed. This will ensure that you get a good photo. It is not uncommon to go through an entire roll of 36 exposures and have only one good shot. NOTE: Don't expect to record more detail than you can see visually in the eyepiece at the time you are photographing. Once you have mastered the technique, experiment with different films, different focal length eyepieces, and even different filters. Long Exposure Prime Focus Photography This is the last form of celestial photography to be attempted after others have been mastered. It is intended primarily for deep sky objects, that is objects outside our solar system which includes star clusters, nebulae, and galaxies. While it may seem that high magnification is required for these objects, just the opposite is true. Most of these objects cover large angular areas and fit nicely into the prime focus field of your telescope. The brightness of these objects, however, requires long exposure times and, as a result, are rather difficult. 44 There are several techniques for this type of photography, and the one chosen will determine the standard accessories needed. The best method for long exposure deep sky astrophotography is with an off-axis guider. This device allows you to photograph and guide through the telescope simultaneously. Celestron offers a very special and advanced offaxis guider, called the Radial Guider (#94176). In addition, you will need a T-Ring to attach your camera to the Radial Guider. Other equipment needs include a guiding eyepiece. Unlike other forms of astrophotography which allows for fairly loose guiding, prime focus requires meticulous guiding for long periods. To accomplish this you need a guiding ocular with an illuminated reticle to monitor your guide star. For this purpose, Celestron offers the Micro Guide Eyepiece (#94171) Here is a brief summary of the technique. 1. 2. 3. 4. 5. 6. 7. 8. 9. Polar align the telescope. For more information on polar aligning, see the Polar Alignment section earlier in the manual. Remove all visual accessories. Thread the Radial Guider onto your telescope. Thread the T-Ring onto the Radial Guider. Mount your camera body onto the T-Ring the same as you would any other lens. Set the shutter speed to the "B" setting. Focus the telescope on a star. Center your subject in the field of your camera. Find a suitable guide star in the telescope field. This can be the most time consuming process. 10. Open the shutter using a cable release. 11. Monitor your guide star for the duration of the exposure using the buttons on the hand controller to make the needed corrections. 12. Close the camera's shutter. Periodic Error Correction (PEC) PEC for short, is a system that improves the tracking accuracy of the drive by reducing the number of user corrections needed to keep a guide star centered in the eyepiece. PEC is designed to improve photographic quality by reducing the amplitude of the worm errors. Using the PEC function is a three-step process. First, the CGE needs to know the current position of its worm gear so that it has a reference when playing back the recorded error. Next, you must guide for at least 8 minutes during which time the system records the correction you make. (It takes the worm gear 8 minutes to make one complete revolution, hence the need to guide for 8 minutes). This "teaches" the PEC chip the characteristics of the worm. The periodic error of the worm gear drive will be stored in the PEC chip and used to correct periodic error. The last step is to play back the corrections you made during the recording phase. Keep in mind, this feature is for advanced astrophotography and still requires careful guiding since all telescope drives have some periodic error. 45 Using Periodic Error Correction Once the telescope has been properly polar aligned, select PEC from the Utilities menu and press ENTER to begin recording your periodic error. Here's how to use the PEC function. 1. 2. Find a bright star relatively close to the object you want to photograph. Insert a high power eyepiece with illuminated cross hairs into your telescope. Orient the guiding eyepiece cross hairs so that one is parallel to the declination while the other is parallel to the R.A. axis. Center the guide star on the illuminated cross hairs, focus the telescope, and study the periodic movement. Before actually recording the periodic error, take a few minutes to practice guiding. Set the hand control slew rate to an appropriate guide rate (rate 1 = .5x, rate 2 = 1x) and practice centering the guide star in the cross hairs for several minutes. This will help you familiarize yourself with the periodic error of the drive and the operation of the hand control. Remember to ignore declination drift when programming the PEC. 3. 4. Note: When recording PEC only the photo guide rates (rates 1 and 2) will be operational. This eliminates the possibility of moving the telescope suddenly while recording. 5. To begin recording the drive's periodic error, press the MENU button and select PEC from the Utilities menu. Use the Up/Down scroll buttons to display the Record option and press ENTER. You will have 5 seconds before the system starts to record. The first time each observing session that PEC record or play is selected, the worm gear must rotate in order to mark its starting position. If the rotation of the worm gear moves your guide star outside the field of view of the eyepiece, it will have to be re-centered before the recording begins. Helpful Hint Once the worm gear is indexed, it will not need to be positioned again until the telescope is turned-off. So, to give yourself more time to prepare for guiding, it is best to restart PEC recording after the worm gear has found its index. 6. 7. 8. After 8 minutes PEC will automatically stop recording. Point the telescope at the object you want to photograph and center the guide star on the illuminated cross hairs and you are ready to play back the periodic error correction. Once the drive's periodic error has been recorded, use the Playback function to begin playing back the correction for future photographic guiding. If you want to re-record the periodic error, select Record and repeat the recording processes again. The previously recorded information will be replaced with the current information. Repeat steps 7 and 8 to playback the PEC corrections for your next object. Does the PEC function make unguided astrophotography possible? Yes and no. For solar (filtered), lunar, and piggyback (up to 200mm), the answer is yes. However, even with PEC, off-axis guiding is still mandatory for long exposure, deep sky astrophotography. The optional Reducer/Corrector lens reduces exposure times making the task of guiding a little easier. When getting started, use fast films to record as much detail in the shortest possible time. recommendations: · Ektar 1000 (color print) Here are proven 46 · · · · · · Konica 3200 (color print) Fujichrome 1600D (color slide) 3M 1000 (color slide) Scotchchrome 400 T-Max 3200 (black and white print) T-Max 400 (black and white print) As you perfect your technique, try specialized films, that is films that are designed or specially treated for celestial photography. Here are some popular choices: · · · · Ektar 125 (color print) Fujichrome 100D (color slide) Tech Pan, gas hypered (black and white print) T-Max 400 (black and white print) There is no exposure determination table to help you get started. The best way to determine exposure length is look at previously published photos to see what film/exposure combinations were used. Or take unguided sample photos of various parts of the sky while the drive is running. Always take exposures of various lengths to determine the best exposure time. Terrestrial Photography Your CGE makes an excellent telephoto lens for terrestrial (land) photography. Terrestrial photography is best done will the telescope in Alt-Az configuration and the tracking drive turned off. To turn the tracking drive off, press the MENU (9) button on the hand control and scroll down to the Tracking Mode sub menu. Use the Up and Down scroll keys (10) to select the Off option and press ENTER. This will turn the tracking motors off, so that objects will remain in your camera's field of view. Metering The CGE has a fixed aperture and, as a result, fixed f/ratios. To properly expose your subjects photographically, you need to set your shutter speed accordingly. Most 35mm SLR cameras offer through-the-lens metering which lets you know if your picture is under or overexposed. Adjustments for proper exposures are made by changing the shutter speed. Consult your camera manual for specific information on metering and changing shutter speeds. Reducing Vibration Releasing the shutter manually can cause vibrations, producing blurred photos. To reduce vibration when tripping the shutter, use a cable release. A cable release keeps your hands clear of the camera and lens, thus eliminating the possibility of introducing vibration. Mechanical shutter releases can be used, though air-type releases are best. Blurry pictures can also result from shutter speeds that are too slow. To prevent this, use films that produce shutter speeds greater than 1/250 of a second when hand-holding the lens. If the lens is mounted on a tripod, the exposure length is virtually unlimited. Another way to reduce vibration is with the Vibration Suppression Pads. These pads rest between the ground and tripod feet. They reduce the vibration amplitude and vibration time. CCD Imaging Fastar Lens Assembly Option ­ Using your CGE telescope at f/2 with optional Fastar Lens Assembly The CGE800, CGE1100 and CGE1400 telescope are equipped with a removable secondary mirror that allows you to convert your f/10 telescope into an f/2 imaging system capable of exposure times 25 times shorter than those needed with a f/10 system! With the optional Fastar lens assembly you can easily convert your Fastar compatible telescope to f/2 prime focus use in a matter of seconds. The Fastar 47 Secondary Mirror Secondary Mirror Retaining Ring Corrector Plate Secondary Mirror Mount Handle Figure 7-2 The Fastar Compatible Optical System compatible CGE telescope's versatility allows it to be used in many different f-number configurations for CCD imaging. It can be used at f/2 (with optional Fastar Lens Assembly), f/6.3 (with the optional Reducer/Corrector), f/10, and f/20 (with the optional 2x Barlow) making it the most versatile imaging system available today. This makes the system ideal for imaging deep-sky objects as well as planetary detail. Described below is the configuration of each F-number and the type of object best suited to that kind of imaging. The above figure shows how the secondary mirror is removed when using the optional CCD camera at f/2 and the Fastar Lens Assembly. Warning: The secondary mirror should never be removed unless installing the optional Fastar Lens Assembly. Adjustments to collimation can easily be made by turning the screws on the top of the secondary mirror mount without ever having to remove the secondary mirror (see Telescope Maintenance section of this manual). The F/# stands for the ratio between the focal length and the diameter of the light gathering element. A CGE1100 optical tube has a focal length of 110 inches and a diameter of 11 inches. This makes the system an f/10, (focal length divided by diameter). The CGE 800 has a focal length of 80 inches and a diameter of 8 inches, also making it an f/10 optical system. However, the CGE 1400 optical tube has a 154 inch focal length with a F-ratio of f/11. When the secondary is removed and the CCD camera is placed at the Fastar position, the system becomes f/2, this is a unique feature to some Celestron telescopes (see figures below). 48 Fastar L ens Assem bl CCD Camera Figure 7-3 Figure 7-4 The key factors for good CCD imaging are; exposure time, field-of-view, image size, and pixel resolution. As the F/# goes down (or gets faster), the exposure times needed decreases, the field-of-view-increases, but the image scale of the object gets smaller. What is the difference between f/2 and f/10? F/2 has 1/5 the focal length of f/10. That makes the exposure time needed about 25 times shorter than at f/10, the field of view 5 times larger and the object size 1/5 compared to that of f/10. (see Table below)