User manual SBIG ST-5

CCD Camera Operating Manual for the Model ST-4X, ST-5 and ST-6 Santa Barbara Instrument Group 1482 East Valley Road Santa Barbara, CA 93108 Phn (805) 969-1851 Fax (805) 969-4069 Note: This equipment has been tested and found to comply with the limits for a Class B digital device pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures: · · · · Reorient or relocate the receiving antenna. Increase the separation between the receiver and the equipment. Connect the equipment into an outlet on a circuit different from that to which the receiver is connected. Consult the dealer or an experienced radio/TV technician for help. Changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate the equipment. Also note that user must use shielded interface cables in order to maintain product within FCC compliance. CCDOPS Manual Revision 2A January 1996 Table of Contents 1. 1.1. 1.2. Introduction ............................................................................................................1 Road Map of the Documentation ............................................................................1 Quick Tour...............................................................................................................1 1.2.1. CCDOPS Software .................................................................................1 1.2.2. CCD Camera..........................................................................................2 Introduction to CCD Cameras................................................................................3 Cameras in General..................................................................................................3 How CCD Detectors Work ......................................................................................3 2.2.1. The ST-4X CCD and Frame Transfer CCDs...........................................4 Camera Hardware Architecture ..............................................................................5 CCD Special Requirements......................................................................................7 2.4.1. Cooling...................................................................................................7 2.4.2. Readout Types .......................................................................................8 2.4.3. Dark Frames...........................................................................................8 2.4.4. Flat Field Images....................................................................................8 2.4.5. Pixels vs. Film Grains.............................................................................9 Electronic Imaging ...................................................................................................9 Black and White vs. Color...................................................................................... 10 At the Telescope with a CCD Camera ................................................................. 13 Step by Step with a CCD Camera.......................................................................... 13 Attaching the Camera to the Telescope................................................................. 13 Establishing a Communications Link.................................................................... 15 Focusing the CCD Camera .................................................................................... 15 Finding and Centering the Object.......................................................................... 17 Taking an Image .................................................................................................... 17 Displaying the Image............................................................................................. 17 Processing the Image ............................................................................................. 17 Advanced Capabilities........................................................................................... 18 3.9.1. Crosshairs Mode (Photometry and Astrometry)................................. 18 3.9.2. Sub-Frame Readout in Focus............................................................... 18 3.9.3. Track and Accumulate......................................................................... 19 3.9.4. Autoguiding......................................................................................... 19 3.9.5. Auto Grab ............................................................................................ 20 3.9.6. Color Imaging ...................................................................................... 20 Camera Hardware ................................................................................................. 21 System Components .............................................................................................. 21 Connecting the Power............................................................................................ 21 Connecting to the Computer ................................................................................. 22 Connecting the Relay Port to the Telescope .......................................................... 23 Modular Family of CCD Cameras ......................................................................... 26 Camera Software Reference ................................................................................. 31 Different Host Computers ..................................................................................... 31 5.1.1. Installing the Software......................................................................... 31 5.1.2. The CCDOPS User Interface................................................................ 32 5.1.3. CCDOPS for IBM PCs.......................................................................... 35 2. 2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 3. 3.1. 3.2. 3.3. 3.4. 3.5. 3.6. 3.7. 3.8. 3.9. 4. 4.1. 4.2. 4.3. 4.4. 4.5. 5. 5.1. i 5.2. Command Mode.................................................................................. 35 Graphics Mode..................................................................................... 36 5.1.4. CCDOPS on Macintosh Computers .................................................... 37 CCDOPS Menus and Commands.......................................................................... 37 5.2.1. Command Tree .................................................................................... 37 5.2.2. File Menu on the Macintosh ................................................................ 39 5.2.3. File Menu on the PC ............................................................................ 40 Save FITS Command............................................................................ 41 Save TIFF Command ........................................................................... 42 5.2.4. Edit Menu on the Macintosh ............................................................... 43 5.2.5. Camera Menu ...................................................................................... 44 Grab Command ................................................................................... 45 Auto Grab Command .......................................................................... 46 Focus Command.................................................................................. 47 Macintosh Focus Window ................................................................... 49 PC Focus Mode Menus ........................................................................ 50 ST-4X Camera Setup Command.......................................................... 51 ST-5 Camera Setup Command ............................................................ 52 ST-6 Camera Setup Command ............................................................ 53 5.2.6. Display Menu on the Macintosh.......................................................... 54 5.2.7. Display Menu on the PC...................................................................... 55 Display Image Command.................................................................... 56 PC Display Mode Menus..................................................................... 57 Macintosh Contrast Window............................................................... 59 Macintosh Color Table Editor.............................................................. 60 5.2.8. Utility Menu......................................................................................... 61 Edit Parameters Command.................................................................. 63 5.2.9. Misc Menu ........................................................................................... 64 Mac Setup Command .......................................................................... 65 PC Setup Command ............................................................................ 66 Telescope Setup Command ................................................................. 67 5.2.10. Track Menu.......................................................................................... 68 Track and Accumulate Command....................................................... 69 Calibrate Track Command................................................................... 70 Tracking Parameters Command.......................................................... 71 5.2.11. Filter Menu........................................................................................... 73 Filter Setup Command......................................................................... 74 Advanced Imaging Techniques ........................................................................... 75 Lunar and Planetary Imaging................................................................................ 75 Deep Sky Imaging.................................................................................................. 75 Terrestrial Imaging ................................................................................................ 76 Taking a Good Flat Field ....................................................................................... 76 Building a Library of Dark Frames........................................................................ 76 Changing the Camera Resolution.......................................................................... 77 Making Astrometric and Photometric Measurements .......................................... 77 6.7.1. Astrometric Measurements.................................................................. 77 6.7.2. Photometric Measurements. ................................................................ 79 6.7.3. Calculation of Centroids...................................................................... 80 6.7.4. Calculation of Separation..................................................................... 81 6.7.5. Calculation of Magnitude.................................................................... 81 6.7.6. Calculation of Diffuse Magnitude ....................................................... 82 Flat Fielding Track and Accumulate Images......................................................... 82 6. 6.1. 6.2. 6.3. 6.4. 6.5. 6.6. 6.7. 6.8. ii 6.9. 6.10. 7. 7.1. 7.2. 7.3. 7.4. Tracking Functions ................................................................................................ 84 PC COM Port Compatibility Testing..................................................................... 85 Accessories for your CCD Camera....................................................................... 87 Tri-color Imaging ................................................................................................... 87 Camera Lens Adapters and Eyepiece Projection................................................... 87 Focal Reducers ....................................................................................................... 87 Third Party Products and Services ........................................................................ 87 7.4.1. Windows Software............................................................................... 87 7.4.2. Image Processing Software.................................................................. 88 7.4.3. Getting Hardcopy ................................................................................ 88 SBIG Technical Support......................................................................................... 88 Common Problems ............................................................................................... 89 Glossary................................................................................................................. 93 Appendix A - Connector Pinouts ......................................................................... 97 Using RS422 on the PC .......................................................................................... 98 SBIG Tracking Interface Cable (TIC) ..................................................................... 98 Appendix B - SBIG File Formats.......................................................................... 99 SBIG Image Formats .............................................................................................. 99 B.1.1 Type 3 Format...................................................................................... 99 B.1.2. Image Compression ........................................................................... 101 PC Color Table Formats....................................................................................... 102 TIFF Format ......................................................................................................... 103 FITS Format.......................................................................................................... 103 Appendix C - Maintenance................................................................................. 105 Replacing the Fuse............................................................................................... 105 Cleaning the CCD and the Window.................................................................... 105 C.2.1 Cleaning the ST-4X and ST-5 ............................................................. 105 C.2.2 Cleaning the ST-6............................................................................... 105 Replacing the Desiccant in the ST-6..................................................................... 106 Appendix D - Cross Platform Compatibility .................................................... 107 7.5. 8. 9. A.1. A.2. A.3. B. B.1. B.2. B.3. B.4. C. C.1. C.2. C.3. D. iii Section 1 - Introduction 1. Introduction Congratulations and thank you for buying one of Santa Barbara Instrument Group's CCD cameras. The model ST-4X, ST-5 and ST-6 represent the state of the art in CCD camera systems with their low noise and advanced capabilities. We feel that these cameras will expand your astronomy experience by being able to easily take images like the ones you've seen in books and magazines, but never seen when peeking through the eyepiece. SBIG CCD cameras offer convenience, high sensitivity (a typical deep-sky image is only two to ten minutes), and advanced image processing techniques that film just can't match. While CCDs will probably never replace film in its large format, CCDs allow a wide range of scientific measurements and have established a whole new field of Astronomy that is growing by leaps and bounds. 1.1. Road Map of the Documentation This manual describes the ST-4X, ST-5, and ST-6 CCD Camera Systems from Santa Barbara Instrument Group. For new users to the field of CCD Astronomy, Sections 2, 3 and 4 offer introductory material about CCD Cameras and their uses in Astronomy. Users who are familiar with CCD cameras may wish to skip section 2 and browse through sections 3 and 4, reading any new material. Thoroughly experienced SBIG customers may wish to jump right into section 5 which gives detailed and specific information about the SBIG software. This section is written more as a reference than as general reading. Sections 6 and 7 offer hints and information about advanced imaging techniques and accessories for CCD imaging that you may wish to read after your initial telescope use of the CCD camera. Finally, section 8 may be helpful if you experience problems with your camera, and the Appendices provide a wealth of technical information about these systems. 1.2. Quick Tour This section is a quick guided tour of the CCD Camera System you have just purchased. If you're like most people you want to get started right away and dispense with the manual. Use this section as a guide for learning about your new system. 1.2.1. CCDOPS Software Follow the instructions below to run the CCDOPS software and display and process sample images included on the distribution diskette. · For this quick tour you can run the CCDOPS software from the distribution floppy disk or you can install the software on our hard disk (refer to Section 5.1.1). On the Macintosh you can double-click on the CCDOPS icon. On the PC you should make the CCDOPS floppy or directory the active directory then give DOS the CCDOPS command. Use the Open command in the File menu to load one of the sample images. On the Macintosh the image is displayed automatically. On the PC you then use the Image command in the Display menu to display the image. · · · Page 1 Section 1 - Introduction · Try using the crosshairs. On the Macintosh use the Show Crosshairs command in the Display menu. On the PC hit the 'X' key. Use the mouse or arrow keys to move the crosshair around in the image and see the pixel values. Quit the crosshairs and try inverting the image. On the Macintosh you check the Invert checkbox and then click the Do It button in the Contrast window. On the PC you hit the Esc key to quit the Crosshairs mode, then hit the 'N' key. Try the photo display mode. On the Macintosh use the Photo Mode command in the Display Menu. On the PC you exit the display mode by hitting the Esc key and then use the Display Image command again, this time selecting the Photo Display mode instead of the Analysis mode. Load up the other sample images and display them using the photo display mode. · · · 1.2.2. CCD Camera Unfortunately there really aren't many shortcuts you can take when using the CCD camera to capture images. The instructions below refer you to various sections of the manual. · · · · · Insert the CCD Camera into the telescope and focus on a star (refer to Sections 3.2 and 3.3). Find some relatively bright object like M51, the Ring Nebula (M57) or the Dumbbell Nebula (M27) (refer to section 3.5). Take a 2 minute exposure using the Grab command with the Dark frame option set to Also (refer to Section 3.6). Display the image (refer to Section 3.7). Process the image (refer to Section 3.8). If you happen to have purchased a camera lens adapter for your CCD Camera you can use that to take images in the daytime. Additionally you could make a small pin-hole aperture out of a piece of aluminum foil after wrapping it around the camera's nosepiece. · · · · · Shut down the f stop all the way to f/16 or f/22. Set the focus based upon the object and the markings on the lens. Take a 1 second exposure with the Grab command. Display the image (refer to Section 3.7). Process the image (refer to Section 3.8). Page 2 Section 2 - Introduction to CCD Cameras 2. Introduction to CCD Cameras This section introduces new users to CCD (Charge Coupled Device) cameras and their capabilities and to the field of CCD Astronomy and Electronic Imaging. 2.1. Cameras in General The CCD is very good at the most difficult astronomical imaging problem: imaging small, faint objects. For such scenes long film exposures are typically required. The CCD based system has several advantages over film: greater speed, quantitative accuracy, ability to increase contrast and subtract sky background with a few keystrokes, the ability to co-add multiple images without tedious dark room operations, wider spectral range, and instant examination of the images at the telescope for quality. Film has the advantages of a much larger format, color, and independence of the wall plug (the SBIG family of cameras can be battery operated in conjunction with a laptop computer, though). After some use you will find that film is best for producing sensational large area color pictures, and the CCD is best for planets, small faint objects, and general scientific work such as variable star monitoring and position determination. It is for this reason that we designed our cameras to support both efforts, as a stand-alone tracker, in the case of the ST-4, and as a tracker/imaging camera in the case of the other SBIG CCD products. 2.2. How CCD Detectors Work The basic function of the CCD detector is to convert an incoming photon of light to an electron which is stored in the detector until it is read out, thus producing data which your computer can display as an image. It doesn't have to be displayed as an image. It could just as well be displayed as a spreadsheet with groups of numbers in each cell representing the number of electrons produced at each pixel. These numbers are displayed by your computer as shades of gray for each pixel site on your screen thus producing the image you see. How this is accomplished is eloquently described in a paper by James Janesick and Tom Elliott of the Jet Propulsion Laboratory: "Imagine an array of buckets covering a field. After a rainstorm, the buckets are sent by conveyor belts to a metering station where the amount of water in each bucket is measured. Then a computer would take these data and display a picture of how much rain fell on each part of the field. In a CCD the "raindrops" are photons, the "buckets" the pixels, the "conveyor belts" the CCD shift registers and the "metering system" an on-chip amplifier. Technically speaking the CCD must perform four tasks in generating an image. These functions are 1) charge generation, 2) charge collection, 3) charge transfer, and 4) charge detection. The first operation relies on a physical process known as the photoelectric effect - when photons or particles strikes certain materials free electrons are liberated...In the second step the photoelectrons are collected in the nearest discrete collecting sites or pixels. The collection sites are defined by an array of electrodes, called gates, formed on the CCD. The third operation, charge transfer, is accomplished by manipulating the voltage on the gates in a systematic way so the signal electrons move down the vertical registers from one pixel to the next in a conveyor-belt like fashion. At the end of each column is a horizontal register of pixels. This register collects a line at a time and then Page 3 Section 2 - Introduction to CCD Cameras transports the charge packets in a serial manner to an on-chip amplifier. The final operating step, charge detection, is when individual charge packets are converted to an output voltage. The voltage for each pixel can be amplified offchip and digitally encoded and stored in a computer to be reconstructed and displayed on a television monitor."1 Output Readout Register Y=1 Amplifier Y=N X=1 Figure 2.1 - CCD Structure X=M 2.2.1. The ST-4X CCD and Frame Transfer CCDs In the ST-4X, the CCD is read out electronically by shifting each row of pixels into a readout register at the Y=0 position of the CCD, and then shifting the row out through an amplifier at the X=0 position. The entire array shifts up one row when a row is shifted into the readout register, and a blank row is inserted at the Y=164 position. Note that the CCD elements are still collecting light as they step up to the readout register. The ST-5 and ST-6 CCD cameras use a more advanced CCD which is known as a frame transfer CCD. In these devices all active pixels are shifted very quickly into a pixel array screened from the light by a metal layer, and then read out. The ST-4X CCD minimizes the effect of not having a frame transfer buffer by reading out the array relatively quickly, reading 30,000 pixels in about 0.7 seconds. As long as the CCD exposure is greater than about one second this technique will reduce streaking of the stars to acceptable levels. Planets pose a particular problem to the ST-4X CCD since they are so bright that exposures of 1 second at f/10 are badly overexposed. The ST-4X has a "Half Frame" mode for planets and bright stars to solve this problem. In the Half Frame mode the upper half of the CCD is used as a frame buffer for a bright object positioned in the lower half of the CCD as shown below in Figure 2.2. A short exposure can be taken and the bottom half of the array shifted rapidly up to the upper half. The 82 lines of short exposure data can then be readout at the normal rate. This method works quite well, and uses enough pixels such that 0.5 arcsecond per pixel scale factors can be achieved while viewing an entire planet. 1 "History and Advancements of Large Area Array Scientific CCD Imagers", James Janesick, Tom Elliott. Jet Propulsion Laboratory, California Institute of Technology, CCD Advanced Development Group. Page 4 Section 2 - Introduction to CCD Cameras Figure 2.2 - ST-4X Half Frame Positioning When using the original ST-4 for a long exposure, a glow was present in the upper left corner of the image, near pixel (1,1). This was due to an electrical luminescence in the readout electronics that could saturate the array in the corner in exposures several minutes long. This glow has been essentially eliminated in the ST-4X. 2.3. Camera Hardware Architecture This section describes the SBIG CCD camera from a systems standpoint. It describes the elements that comprise a CCD camera and the functions they provide. Please refer to Figure 2.3 below as you read through this section. Optical Head CCD Clock Drivers Postamp/ A/D Converter Preamp TE Cooler Frame Store Microcontroller Host Computer Power Supply CPU RS232 Figure 2.3 - CCD System Block Diagram At the "front end" of any CCD camera is the CCD sensor itself. As we have already learned, CCD detectors are a solid state image sensor organized in a rectangular array of regularly Page 5 Section 2 - Introduction to CCD Cameras spaced rows and columns. Table 2.1 below lists some interesting aspects of the various CCDs used in the ST-4X, ST-5 and ST-6 cameras. Camera ST-4X ST-5 ST-6 CCD TC211 TC255 TC241 Array Number of Dimensions Pixels 2.6 x 2.6 mm 192 x 164 3.2 x 2.4 mm 320 x 240 8.6 x 6.5 mm 375 x 242 Table 2.1 - Camera CCD Configurations Pixel Sizes 13.75 x 16 µ 10 x 10 µ 23 x 27 µ The CCD is cooled by mounting it on the cold side of a thermoelectric (TE) cooler. The TE cooler pumps heat out of the CCD with its own internally generated heat and dissipates it into a heat sink which forms part of the optical head's mechanical housing. In SBIG cameras this waste heat is dumped into the air using passive radiators, making the design and operation of the heads simple and not inconvenienced by requirements for liquid recirculation cooling. Since the CCD is cooled below 0°C, some provision must be made to prevent frost from forming on the CCD. SBIG cameras have the CCD/TE Cooler mounted in a windowed hermetic chamber sealed with an O-Ring. The hermetic chamber does not need to be evacuated, another "ease of use" feature we employ in the design of our Optical heads. Keeping the size of the hermetic chamber small (in the case of the ST-4X and ST-5) or using desiccant in the chamber (ST-6) keeps the total amount of moisture that can condense small. Other elements contained in the optical head include the preamplifier and an electromechanical vane (in the case of the ST-6). The vane makes taking dark frames a simple matter of pushing a button on the computer. We refer to this as a vane rather than a shutter because it does not perform the task of timing the exposure, it merely blocks the light from the CCD to facilitate taking dark images. Timing of exposures in SBIG cameras is based upon the clocking scheme applied to the CCDs. As far as the ST-4X and ST-5 are concerned, that's all of the system components contained in the optical head unit, owing to its small size. The Clock Drivers and the PostAmp/Analog to Digital Converter reside in different places in the ST-4X/ST-5 and the ST-6. The Clock Drivers adapt the logic-level signals from the CPU's microcontroller to the voltage levels and sequences required by the CCD. Clocking the CCD transfers charge in the array and is used to clear the array or read it out. The Postamp further amplifies and conditions the CCD's output signal for digitization by the Analog to Digital Converter (A/D). In the ST-6 both the clock drivers and the A/D are contained on a board in the optical head. In the ST-4X and ST-5 these electronics are on a board in the lower half of the CPU. This leaves to be discussed only the elements in the CPU, namely the Microcontroller, the Frame Store, and the Power Supply. The microcontroller is a 9.2 MHz 80188 microcontroller, based upon the 8088 microprocessor used in the IBM PC. It controls the operation of the CCD camera at the lowest level, receiving commands from the Host Computer and executing sequences of instructions to control and acquire images. The frame store allows holding three images in the CPU (a light image, a dark image, and a double-precision accumulation image). Finally, the power supply takes the supplied 12 Volts and produces the various regulated voltages required by the CPU in addition to a variable output supply for powering the TE Cooler. Although not part of the CCD Camera itself, the Host Computer and Software are an integral part of the system. SBIG provides software for its cameras that support both the IBM Page 6 Section 2 - Introduction to CCD Cameras PC (and Compatible) and Macintosh computers. The software allows image acquisition, image processing, and auto guiding with ease of use and professional quality. Many man-years and much customer feedback has gone into the SBIG software and it is unmatched in its capabilities. 2.4. CCD Special Requirements This section describes the unique features of CCD cameras and the special requirements that CCD systems impose. 2.4.1. Cooling Random noise and dark current combine to place a lower limit on the ability of the CCD to detect faint light sources. If the CCD is producing more electrons from its own internal processes than is produced by photons from a distant object, the signal from the object is said to be "lost in the noise", and will be impossible to display without sophisticated image processing software. The same is true if the immediate environment is producing the noise. There are several sources of noise, both internal and external which can contribute to this problem. Noise here refers to the "gritty" look of short exposure images. Internally, the CCD generates thermal noise and readout noise caused by the operation of the electronics on the chip. In unusual circumstances, radio frequency interference can contaminate the CCD just as it can affect your television set or radio, but this is rarely a problem in normal operating environments. Power lines, switches turning on and off, spark plugs, even cosmic rays will register if conditions are right. Of course, there is one external source of "noise" you do not want to eliminate - the photons coming from the object you are imaging! So the trick is to eliminate unwanted sources of electron production in the chip and thus make the detector more sensitive to the remaining source of electron production by incoming photons. As you can imagine, the reduction of unwanted noise is important for the best performance of the CCD. The user will naturally have to do his or her best to reduce external sources of noise in the environment. The internal noise of SBIG cameras is kept to an absolute minimum by using state of the art technology. Dark current is thermally generated electrons in the device itself. All CCDs have dark current which can cause each pixel to fill with electrons in only a few seconds at room temperature even in the absence of light. By cooling the CCD, this source of noise is reduced, the sensitivity increased, and longer exposures are possible. In fact, for every 8°C of additional cooling, the dark current in the CCD is reduced to half. All SBIG cameras use a thermoelectric (TE) cooler to cool the CCD. The ST-4X and ST-5 have a single stage cooler whereas the larger format ST-6 utilizes a two stage cooler. The ST-5 and ST-6 have temperature sensing thermistors on the CCD mount to monitor the temperature, and the CPU controls the temperature at a user determined value for long periods. As a result, exposures hours long are possible, and saturation of the CCD by the sky background typically limits the exposure time. The temperature regulation feature of the ST-5 and ST-6 also means that one dark frame can be used for similar exposures on several nights. The sky background conditions also increase the noise in images, and in fact, as far as the CCD is concerned, there is no difference between the noise caused by dark current and that from sky background. If your sky conditions are causing photoelectrons to be generated at the rate of 100 e-/pixel/sec for example, increasing the cooling beyond the point where the dark current is roughly half that amount will not improve the quality of the image. This very reason Page 7 Section 2 - Introduction to CCD Cameras is why deep sky filters are so popular with astrophotography. They reduce the sky background level, increasing the contrast of dim objects. 2.4.2. Readout Types In order to read out the values of the charge stored in the pixels as they are shifted to the readout amplifiers, the charge is stored temporarily on a capacitor. This capacitor converts the optically generated charge to a voltage level for the output amplifier to sense. When the readout process for the previous pixel is completed, the capacitor is drained and the next charge shifted, read, and so on. However, each time the capacitor is drained, some residual charge remains. This residual charge is actually the dominant noise source in CCD readout electronics. This residual charge may be measured before the next charge is shifted in, and the actual difference calculated. This is called double correlated sampling. It produces more accurate data at the expense of longer read out times (two measurements are made instead of one). If the accuracy of the data is not critical, as in finding objects or focusing, the extra time spent in double correlated sampling is not necessary. In this case a rapid readout mode may be available which ignores the small residual charge. 2.4.3. Dark Frames No matter how much care is taken to reduce all sources of unwanted noise, some will remain. Fortunately, however, due to the nature of electronic imaging and the use of computers for storing and manipulating data, this remaining noise can be drastically reduced by the subtraction of a dark frame from the raw light image. A dark frame is simply an image taken at the same temperature and for the same duration as the light frame with the source of light to the CCD blocked so that you get a "picture" of the dark. This dark frame will contain an image of the noise caused by dark current (thermal noise) and other fixed pattern noise such as read out noise. When the dark frame is subtracted from the light frame, this pattern noise is removed from the resulting image. 2.4.4. Flat Field Images Another way to compensate for certain unwanted optical effects is to take a "flat field image" and use it to correct for variations in pixel response uniformity across the area of your darksubtracted image. You take a flat field image of a spatially uniform source and use the measured variations in the flat field image to correct for the same unwanted variations in your images. The Flat Field command allows you to correct for the effects of vignetting and nonuniform pixel responsivity across the CCD array. The Flat Field command is very useful for removing the effects of vignetting that may occur when using a field compression lens. It is difficult to visually tell the difference between a corrected and uncorrected image if there is little vignetting, so you must decide whether to take the time to correct any or all of your dark-subtracted images. It is however always recommended for images that are intended for accurate photometric measurements. Page 8 Section 2 - Introduction to CCD Cameras 2.4.5. Pixels vs. Film Grains Resolution of detail is determined, to a certain degree, by the size of the pixel in the detector used to gather the image, much like the grain size in film. The pixel size of the detector in the ST-4X is 13.75 x 16 microns (1 micron = 0.001mm 0.04 mil). In the ST-5 the pixels are 10 x 10 microns. In the ST-6 the pixels are 23 x 27 microns. Film grain ranges from several hundredths of a micron to several microns depending on the film speed and quality of the emulsion. However, the effects of seeing are probably the limiting factor in any good photograph or electronic image. For example, on a perfect night with excellent optics an observer might hope to achieve sub-arcsecond seeing. More often, however, with the average night sky and even very good optics, seeing may be limited to several arcseconds and you would probably be very satisfied with seeing of one or two arcseconds. Using an ST-5 camera with 10 micron pixels, an 8" f/10 telescope will produce a single pixel angular subtense of one arcsecond, seeing permitting. A 10" f/3 telescope will produce images of 2.6 arcseconds per pixel. If, however, seeing affects the image by limiting resolution to 3 arcseconds, then you would be hard pressed to see any resolution difference between the larger and smaller pixels as you are mostly limited by the sky conditions. Another important consideration is the field of view of the camera. For instance, while the ST-5 has smaller pixels than the ST-6, its area is also smaller, resulting in a corresponding smaller field of view at a given focal length. For comparison, the diagonal measurement of a frame of 35mm film is approximately 40mm, whereas the diagonal dimension of the ST-5 chip is approximately 4mm. The relative CCD sizes for each camera and their corresponding field of view in an 8" f/10 telescope are given below: Camera ST-4X ST-5 ST-6 35mm Array Dimensions Diagonal Field of View at 8" f/10 2.64 x 2.64 mm 3.73 mm 4.5 x 4.5 arcminutes 3.20 x 2.40 mm 4.00 mm 5.6 x 4.2 arcminutes 8.63 x 6.53 mm 10.8 mm 14.6 x 11 arcminutes 36 x 24 mm 43 mm 62 x 42 arcminutes Table 2.2 - CCD Array Dimensions A subtle effect is that, at the same focal length, larger pixels collect more light from nebular regions than small ones, reducing the noise at the expense of resolution. 2.5. Electronic Imaging Electronic images resemble photographic images in many ways. Photographic images are made up of many small particles or grains of photo sensitive compounds which change color or become a darker shade of gray when exposed to light. Electronic images are made up of many small pixels which are displayed on your computer screen to form an image. Each pixel is displayed as a shade of gray, or in some cases a color, corresponding to a number which is produced by the electronics and photo sensitive nature of the CCD camera. However, electronic images differ from photographic images in several important aspects. In their most basic form, electronic images are simply groups of numbers arranged in a computer file in a particular format. This makes electronic images particularly well suited for handling and manipulation in the same fashion as any other computer file. Page 9 Section 2 - Introduction to CCD Cameras An important aspect of electronic imaging is that the results are available immediately. Once the data from the camera is received by the computer, the resulting image may be displayed on the screen at once. While Polaroid cameras also produce immediate results, serious astrophotography ordinarily requires hypersensitized or cooled film, a good quality camera, and good darkroom work to produce satisfying results. The time lag between exposure of the film and production of the print is usually measured in days. With electronic imaging, the time between exposure of the chip and production of the image is usually measured in seconds. Another very important aspect of electronic imaging is that the resulting data are uniquely suited to manipulation by a computer to bring out specific details of interest to the observer. In addition to the software provided with the camera, there are a number of commercial programs available which will process and enhance electronic images. Images may be made to look sharper, smoother, darker, lighter, etc. Brightness, contrast, size, and many other aspects of the image may be adjusted in real time while viewing the results on the computer screen. Two images may be inverted and electronically "blinked" to compare for differences, such as a new supernova, or a collection of images can be made into a large mosaic. Advanced techniques such as maximum entropy processing will bring out otherwise hidden detail. Of course, once the image is stored on a computer disk, it may be transferred to another computer just like any other data file. You can copy it or send it via modem to a friend, upload it to your favorite bulletin board or online service, or store it away for processing and analysis at some later date. We have found the best way to obtain a hard copy of your electronic image is to photograph it directly from the computer screen. You may also send your image on a floppy disk to a photo lab which has digital photo processing equipment for a professional print of your file. Make sure the lab can handle the file format you will send them. Printing the image on a printer connected to your computer is also possible depending on your software/printer configuration. There are a number of software programs available which will print from your screen. However, we have found that without specialized and expensive equipment, printing images on a dot matrix or laser printer yields less than satisfactory detail. However, if the purpose is simply to make a record or catalog the image file for easy identification, a dot matrix or laser printer should be fine. 2.6. Black and White vs. Color The first and most obvious appearance of a CCD image is that it is produced in shades of gray, rather than color. The CCD chip used in SBIG cameras itself is color blind and the pixel values that the electronics read out to a digital file are only numbers representing the number of electrons produced when photons of any wavelength happen to strike its sensitive layers. Of course, there are color video cameras, and a number of novel techniques have been developed to make the CCD chip "see" color. The most common way implemented on commercial cameras is to partition the pixels into groups of three, one pixel in each triplet "seeing" only red, green or blue light. The results can be displayed in color. The overall image will suffer a reduction in resolution on account of the process. A newer and more complicated approach in video cameras has been to place three CCD chips in the camera and split the incoming light into three beams. The images from each of the three chips, in red, green and Page 10 Section 2 - Introduction to CCD Cameras blue light is combined to form a color image. Resolution is maintained. For normal video modes, where there is usually plenty of light and individual exposures are measured in small fractions of a second, these techniques work quite well. However, for astronomical work, exposures are usually measured in seconds or minutes. Light is usually scarce. Sensitivity and resolution are at a premium. The most efficient way of imaging under these conditions is to utilize all of the pixels, collecting as many photons of any wavelength, as much of the time as possible. In order to produce color images in astronomy, the most common technique is to take three images of the same object using a special set of filters and then recombine the images electronically to produce a color composite or RGB color image. SBIG offers as an option a color filter wheel. The accessory is inserted between the telescope and the CCD head. An object is then exposed using a red filter. The wheel is turned until the green filter is in place and another image is taken. Finally a blue image is taken. When all three images have been saved, they may be merged into a single color image using SBIG or third party color software. Page 11 Section 3 - At the Telescope with a CCD Camera 3. At the Telescope with a CCD Camera This section describes what goes on the first time you take your CCD camera out to the telescope. You should read this section throughout before working at the telescope. It will help familiarize you with the overall procedure that is followed without drowning you in the details. It is recommended you first try operating the camera in comfortable surroundings to learns its operation. 3.1. Step by Step with a CCD Camera In the following sections we will go through the steps of setting up and using your CCD camera. The first step is attaching the camera to the telescope. The next step is powering up the camera and establishing a communication link to you computer. Then you will want to get in focus, find an object and take an image. Once you have your light image with a dark frame subtracted, you can display the image and process the results to your liking. Each of these steps is discussed in more detail below. 3.2. Attaching the Camera to the Telescope All SBIG cameras are similar in configuration. The CCD head attaches to the telescope by slipping into the eyepiece holder. A fifteen foot cable runs from the head to the CPU box, which is usually on the ground near the telescope. A ten foot cable connects the host computer's serial port to the CPU box. The CPU is powered by a wall transformer although operation from a car battery is possible. Important Note: Never connect or disconnect the CCD head from the CPU box unless the power switch on the rear side of the CPU box is turned OFF. Damage to the CCD head, or the CPU could occur. Referring to Figure 3.1 below, connect the CCD head to the CPU connector marked "CCD HEAD" with the supplied cable. Next, connect the serial cable to the COM connector along the same front panel of the CPU box and connect the opposite end to the serial port of your computer. Insert the CCD Camera's nosepiece into your telescope's eyepiece holder. You should fully seat the camera against the end of the draw tube so that once focus has been achieved you can swap out and replace the camera without having to refocus. You should orient the camera so that the CCD's axes are aligned in Right Ascension and Declination. Use Figure 3.2 below showing the back of the optical heads as a guide for the proper orientation. Page 13 Section 3 - At the Telescope with a CCD Camera To Host Computer POWER RELAYS COM AUX CCD HEAD Wall Transformer CCD HEAD JUMPER ST-4X/ST-5 Connections To Host Computer POWER RELAYS COM AUX CCD HEAD Wall Transformer ST-6 Connections Figure 3.1 - CPU Connections Next connect the power cable and plug in the transformer. Turn on the CPU by pressing the power switch on the back panel of the CPU box. The red LED in the power switch should glow indicating power has been applied to the unit. When power is applied to the unit, the CPU section is automatically reset. You can manually reset the CPU at any time by pushing the RESET button on the front panel of the CPU, next to the power connector. Pushing reset is only desirable if the camera fails to talk to the host computer. You can hear the relays momentarily engage inside the CPU box with a 'click' when you push in the RESET button. Page 14 Section 3 - At the Telescope with a CCD Camera RA RA DEC DEC ST-4X/ST-5 Orientation ST-6 Orientation Figure 3.2 Orientation of the Optical Head Viewed from Back 3.3. Establishing a Communications Link When the CCDOPS program is initiated it will automatically attempt to establish a link to the camera. This involves identifying the type of CCD head, initializing the offset adjustment in the case of an ST-6 head, and seeking the highest Baud rate. If the software is successful the "Link" field in the Status Window is updated to show the communications parameters achieved. If the camera is not connected or the COM port setting has not yet been properly set, a message will be displayed indicating that the software failed to establish a link to the camera. If this happens, use the PC or Mac Setup command in the Misc menu to configure the CCDOPS software for the serial port you are using. Then use the Establish COM Link command in the Camera Menu to establish communications with the CPU. Note: It is not necessary to have a camera connected to your computer to run the software and display images already saved onto disk. It is only necessary to have a camera connected when you take new images. Once the COM link has been established you may need to set the camera's setpoint temperature in the Camera Setup command. The ST-4X powers up with the TE cooling turned on which will be adequate. The ST-5 and ST-6 power up regulating to whatever temperature the CCD is at which in this case will be the ambient temperature. Use the Camera Setup command and choose a setpoint temperature approximately 40°C below the ambient temperature. 3.4. Focusing the CCD Camera Focusing a CCD camera can be a tedious operation, so a few hints should be followed. Before using the software to focus the camera the first time you should place a diffuser (such as scotch tape or ground glass) at the approximate location of the CCD's sensitive surface behind the eyepiece tube and focus the telescope on the moon, a bright planet or a distant street lamp. This preliminary step will save you much time in initially finding focus. The approximate distance behind the eyepiece tube for each of our CCD cameras is listed in Table 3.1 below: Page 15 Section 3 - At the Telescope with a CCD Camera Camera ST-4X ST-5 ST-6 Distance 0.040 inch 0.050 inch 0.560 inch Diffuser Table 3.1 - Camera Back Focus Back Focus Distance from Table 3.1 To find the fine focus, insert the CCD head into the eyepiece tube, taking care to seat it, and then enter the CCDOPS FOCUS mode. The Focus command automatically displays successive images on the screen as well as the peak brightness value of the brightest object in the field of view. Point the telescope at a 5th to 7th magnitude star (you don't want to focus on bright stars like Sirius because the CCD saturates quickly unless you're way out of focus). If you want, you can center the image on the computer monitor by fine adjusting the telescope position although this is not necessary. As long as the star is in the field of view and not so close to the edge that it will drift out while you are focusing, the positioning is not critical. An exposure of 1 to 3 seconds is recommended to smooth out some of the atmospheric effects. While you can use the Full frame mode to focus, the frame rate or screen update rate can be increased significantly by using Planet mode. In the Planet mode the Focus command takes a full image and then lets you position a variable sized rectangle around the star. On subsequent images the Planet mode only digitizes, downloads, and displays the small area you selected. The increase in frame rate is roughly proportional to the decrease in frame size, assuming you are using a short exposure. The telescope focus is best achieved by maximizing the peak value of the star image. You should be careful to move to a dimmer star if the peak brightness causes saturation. The saturation levels of the various cameras are shown in Table 3.2 below. Another point you should also be aware of is that as you approach a good focus, the peak reading can vary by 30% or so. This is due to the fact that as the star image gets small, where an appreciable percentage of the light is confined to a single pixel, shifting the image a half a pixel reduces the peak brightness as the star's image is split between the two pixels. Camera ST-4X ST-5 ST-6 Saturation Counts 16384 16384 65535 Table 3.2 - Saturation Values Once the best focus is found, the focusing operation can be greatly shortened the second time by removing the CCD head, being careful not to touch the focus knob. Insert a high power eyepiece and slide it back and forth to find the best visual focus, and then scribe the outside of the eyepiece barrel. The next time the CCD is used the eyepiece should be first inserted into the tube to the scribe mark, and the telescope visually focused and centered on the object. At f/6 the depth of focus is only 0.005 inch, so focus is critical. Page 16 Section 3 - At the Telescope with a CCD Camera 3.5. Finding and Centering the Object Once best focus is achieved, we suggest using the Focus command in "Dim" mode to help center objects. This mode gives a full field of view, but reduces resolution in order to increase the digitization and download time. If you have difficulty finding an object after obtaining good focus, check to be sure that the head is seated at best focus, then remove the head and insert a medium or low power eyepiece. Being careful not to adjust the focus knob on the telescope, slide the eyepiece in until the image appears in good focus. Then visually find and center the object, if it is visible to the eye. If not, use your setting circles carefully. Then, reinsert the CCD head and set an exposure time of about ten seconds. Center the object using the telescope hand controls. Note: With a 10 second exposure, objects like M51 or the ring nebula are easily detected with modest amateur telescopes. 3.6. Taking an Image Take a CCD image of the object by selecting the Grab command and setting the exposure time. Star out with the Image size set to full and Auto Display and Auto contrast enabled. The camera will expose the CCD for the correct time, and digitize and download the image. One can also take a dark frame immediately before the light image using the Grab command. In the case of the ST-4X and ST-5 you are reminded to cover the telescope for the dark frame. In the case of the ST-6 the dark frame is taken automatically. Because the ST-5 and ST-6 have regulated temperature control, you may prefer to take and save separate dark images, building up a library at different temperatures and exposure times, and reusing them on successive nights. At the start it's probably easiest to just take the dark frames when you are taking the image. Later, as you get a feel for the types of exposures and setpoint temperatures you use, you may wish to build this library of dark frames. 3.7. Displaying the Image The image can be displayed on the computer screen using the graphics capability of your host computer. Auto contrast can be selected and the software will pick background and range values which are usually good for a broad range of images or the background and range values can be optimized manually to bring out the features of interest. The image can also be displayed as a negative image, or can be displayed with smoothing to reduce the graininess. Once displayed, the image can be analyzed using crosshairs, or can be cropped or zoomed to suit your tastes. 3.8. Processing the Image If not done already, images can be dramatically improved by subtracting off a dark frame of equal exposure for an ST-6. On the ST-4X and ST-5 this effect isn't very dramatic for exposures shorter than a few seconds. You will typically do this as part of the Grab command although it can also be done manually using the Dark Subtract command. By subtracting the dark frame, pixels which have higher dark current than the average, i.e., "hot" pixels, are greatly suppressed and the displayed image appears much smoother. Visibility of faint detail is greatly improved. Page 17 Section 3 - At the Telescope with a CCD Camera The CCDOPS program also supports the use of flat field frames to correct for vignetting and pixel to pixel variations, as well as a host of other image processing commands in the Utility menu. You can smooth or sharpen the image, flip it to match the orientation of published images for comparison or remove hot or cold pixels. 3.9. Advanced Capabilities The following sections describe some of the advanced features of SBIG cameras. While you may not use these features the first night, they are available and a brief description of them is in order for your future reference. 3.9.1. Crosshairs Mode (Photometry and Astrometry) Using the crosshair mode2 enables examination of images on a pixel by pixel basis for such measurements as Stellar and Diffuse Magnitude, and measurement of stellar positions. The 14 to 16 bit accuracy of SBIG systems produces beautiful low-noise images and allows very accurate brightness measurements to be made. With appropriate filters stellar temperature can be measured. Section 6.7 gives detailed information about how you use the crosshair mode to make astrometric and photometric measurements. In the crosshair mode, you move a small cross shaped crosshair around in the image using the keyboard or the mouse. As you position the crosshair, the software displays the pixel value beneath the crosshair and the X and Y coordinates of the crosshair. Also shown is the average pixel value for a box of pixels centered on the crosshair. You can change the size of the averaging box from 3x3 to 11x11 pixels to collect all the energy from a star. 3.9.2. Sub-Frame Readout in Focus The Focus command offers several frame modes for flexibility and increased frame throughput. As previously discussed, the Full frame mode shows the entire field of view of the CCD with the highest resolution, digitizing and displaying all pixels. The Dim mode offers the same field of view but offers higher frame rates by reducing the image's resolution prior to downloading. The resolution is reduced by combining neighboring block of pixels into a "super pixel".3 This reduces the download and display times proportionately, as well improving sensitivity. While you would not want to use the Dim mode for critical focus adjustments due to the large effective pixel, it is great for finding and centering objects. The Planet mode is suggested if high spatial resolution is desired for small objects like planets. The Planet mode allows you to select a small sub-area of the entire CCD for image acquisition. The highest resolution is maintained but you don't have to waste time digitizing and processing pixels that you don't need. Again, the image throughput increase is proportional to the reduction in frame size. One final Focus readout mode is the Spot mode. In Spot mode the entire image is digitized at high resolution, and the image is scanned for the brightest pixel. A small box of pixels surrounding the brightest pixel is then downloaded and displayed. The increase in 2 3 On the PC the Crosshairs mode is accessed through the Display Image command in the Analysis mode. On the Macintosh you use the Show Crosshair command in the Display Menu. The Dim mode combines pixels after they are digitized which is referred to as off-chip binning. Page 18 Section 3 - At the Telescope with a CCD Camera throughput is dependent on the camera being used and can range from 2:1 for an ST-6 which has a slower 16 bit digitization rate to 4:1 on an ST-5 with its faster 14 bit readout. Spot mode is probably most handy for telescopes that suffer from a lot of image shift during focus. Where as Planet mode shows the same area image after image, Spot mode tracks the brightest object around in the field of view. Another aspect of the Focus command and its various modes is the Camera Resolution4 setting in the Camera Setup command. Briefly, the Resolution setting allows trading off image resolution (pixel size) and image capture time while field of view is preserved. High resolution with smaller pixels takes longer to digitize and download than Low resolution with larger pixels. The cameras all support High, Low and Auto resolution modes. The Auto mode is optimized for the Focus command. It automatically switches between Low resolution for Full frame mode to provide fast image acquisition, and High resolution for Planet mode to achieve critical focus. 3.9.3. Track and Accumulate An automatic Track and Accumulate mode (patent pending) is available in CCDOPS which simplifies image acquisition for the typical amateur with an accurate modern drive. These drives, employing PEC or PPEC technology and accurate gears, only need adjustment every 30 to 120 seconds. With Track and Accumulate the software takes multiple exposures and automatically co-registers and co-adds them. The individual exposures are short enough such that drive errors don't show up and the accumulated image has enough integrated exposure to yield a good signal to noise ratio. Procedureally the camera will take an exposure, determine the position of a preselected star, co-register and co-add the image to the previous image in the CPU, and then start the cycle over again. Up to 64 images can be co-added, and the software even allows making telescope corrections between images to keep the object positioned in the field of view. The resulting exposure is almost as good as a single long exposure, depending on the exposure used and sky conditions. The great sensitivity of the CCD virtually guarantees that there will be a usable guide star within the field of view. This new feature provides dramatic performance for the amateur, enabling unattended hour long exposures! 3.9.4. Autoguiding The CCDOPS software allows the ST-4X, ST-5 and ST-6 cameras to be used as autoguiders through the commands in the Track menu. While these systems are not stand-alone, requiring a host computer, they can accurately guide long duration astrophotographs. When functioning as an autoguider, the CCD camera repeatedly takes images of a guide star, measures the star's position to a fraction of a pixel accuracy, and corrects the telescope's position through the hand controller. While autoguiding alleviates the user of the tedious task of staring through an eyepiece for hours at a time, it is by no means an end all cure to telescope drive corrector performance. All the things that were important for good manually guided exposures still exist including a good polar alignment, rigid tubes that are free of flexure 4 The Resolution setting in the Camera Setup command combines pixels before they are digitized. This is referred to as on-chip binning and offers increases in frame digitization rates. Page 19 Section 3 - At the Telescope with a CCD Camera and a moderately good, stable mount and drive corrector. Remember that the function of an auto guider is to correct for the small drive errors and long term drift, not to slew the telescope. One of the reasons that SBIG autoguiders are often better than human guiders is that rather than just stabbing the hand controller to bump the guide star back to the reticule, it gives a precise correction that is the duration necessary to move the guide star right back to its intended position. It knows how much correction is necessary for a given guiding error through the Calibrate Track command. The Calibrate Track command, which is used prior to autoguiding, exercises the telescope's drive corrector in each of the four directions, measuring the displacement of a calibration star after each move. Knowing the displacement and the duration of each calibration move calibrates the drive's correction speed. Once that is known, the CCD tracker gives the drive corrector precise inputs to correct for any guiding error. 3.9.5. Auto Grab The Auto Grab command allows you to take a series of images at a periodic interval and log the images to disk. This can be invaluable for monitoring purposes such as asteroid searches or stellar magnitude measurements. You can even take sub-frame images to save disk space if you don't need the full field of view. 3.9.6. Color Imaging The field of CCD color imaging is relatively new but expanding rapidly. Since all SBIG cameras are equipped with monochromatic CCDs, discriminating only light intensity, not color, some provision must be made in order to acquire color images. SBIG offers a color filter wheel, the CFW-6A, which provides this capability. The color filter wheel allows conveniently placing interference filters in front of the CCD in order to take multiple images in different color bands. These narrow band images are then combined to form a color image. With the SBIG system, a Red, Green and Blue filter are used to acquire three images of the object. The resulting images are combined to form a tri-color image using the CCDCOLOR software. Color imaging places some interesting requirements on the user that bear mentioning. First, many color filters have strong leaks in the infrared (IR) region of the spectrum, a region where CCDs have relatively good response. If the IR light is not filtered out then combining the three images into a color image can give erroneous results. If your Blue filter has a strong IR leak (quite common) then your color images will look Blue. For this reason, SBIG places an IR blocking filter in series with the three color band filters. Second, since you have narrowed the CCD's wavelength response with the interference filters, longer exposures are required to achieve a similar signal to noise compared to what one would get in a monochrome image with wide spectral response. This is added to the fact that tri-color images require a higher signal to noise overall to produce pleasing images. In black and white images your eye is capable of pulling out large area detail out of random noise quite well, whereas with color images your eye seems to get distracted by the color variations in the noisy areas of the image. The moral of the story is that while you can achieve stunning results with CCD color images, it is quite a bit more work. Page 20 Section 4 - Camera Hardware 4. Camera Hardware This section describes the modular components that make up the CCD Camera System and how they fit into the observatory, with all their connections to power and other equipment. 4.1. System Components The ST-4X, ST-5 and ST-6 CCD cameras consist of three major components: the CCD Sensor and Preamplifier, the Readout/Clocking Electronics, and the CPU. Where each of these functions resides varies across the product line. The CCD and Preamplifier are always mounted in the optical head which usually interfaces to the telescope through a 1.25 inch draw tube, sliding into the telescope's focus mechanism. The placement of the physically small preamplifier close to the CCD is necessary to achieve good noise performance. The Readout and Clocking Electronics are housed in the Optical Head in the case of the ST-6, and housed in a second sub-chassis of the CPU in the ST-4X and ST-5. With the ST-6's requirements for larger cooling fin area and the miniaturization of the electronics we were able to fit all the Readout and Control Electronics into the Optical Head of the ST-6. The desire to stay with the smaller format Optical Head in the ST-4X and ST-5 made placing the Readout and Control Electronics with the CPU a necessity. As a side note it's interesting to understand "Why does the ST-6 Optical Head need to be so big"? The reason is heat dissipation. The CCD used in the ST-6 has roughly 6 times the package area of the CCDs used in the ST-4X and the ST-5. A larger package requires a larger amount of cooling to achieve the same operating temperature. In the case of the ST-6 we must pump roughly 1.5 Watts of heat out of the CCD to cool it to -20°C which requires us to supply almost 10 Watts to the two-stage TE cooler. That 10 Watts has to be dissipated into the air, requiring the large fin area found in the ST-6 head. The ST-4X and ST-5 only have to dissipate 2 Watts for the same amount of cooling. The CPU is the master controller of the CCD camera system. Housed within the CPU chassis are a flexible power supply, allowing the unit to run off 12 Volts from a wall transformer or a car battery, a microcontroller, and a frame storage buffer. The microcontroller receives high level commands from the host computer and translates them into sequences of actions. For example when the host computer wants to acquire an image it sends the CPU a "take image" command. The CPU starts by clearing the CCD with the necessary clocking, times the exposure, and at the end of the exposure clocks the CCD again with a readout sequence, storing the digitized data in the frame storage buffer. All this happens while the CCD's temperature is being regulated and communications with the host computer are being maintained. 4.2. Connecting the Power The power supply in the CPU is designed to run off 12 Volts AC or DC. Most users will find using the wall transformer supplied with the systems to be the most convenient way to power the system. In the field however, battery operation is the most logical choice. In that case you can simply unscrew the power cable from the wall transformer and attach it to the battery. AC systems (like the wall transformer) do not have a fixed polarity: swapping the leads at the transformer does not make a difference as far as the operation of the CPU is concerned since the output of the transformer is isolated from any other grounds in the system. When powering the Page 21 Section 4 - Camera Hardware CPU with a DC supply the polarity of the applied voltage is important, mainly because it is common in DC systems to connect the negative lead to ground. When powering the CPU from a battery or DC power supply observe the polarities shown in Table 4.1 below for the Power Connector on the CPU: Voltage Power Connection +12V to +15V Pin 9 0V or Ground Pin 4 Table 4.1 - CPU Power Connections One interesting item about the design of the power supply in the CPU bears mentioning. The power supply, which is a switching power supply, offers very high efficiency but has an unusual characteristic. As the input voltage to the power supply drops (due to brownouts or overall low voltage) the current increases to accommodate the voltage drop. At some point the CPU will detect that the input voltage has dropped too much and will shut down the TE Cooler (the largest current drain) in an attempt to not over current the transformer. If this occurs the host software will tell you about it. If it happens repeatedly you might suspect that the voltage supply to the wall transformer is low, possibly due to voltage drops in a long extension cord, etc. Foreign users of SBIG systems may need to obtain a local version of the wall transformer as SBIG does not supply them. A trip to your local "Radio Shack" may be necessary to find a 12V, 20VA transformer for the ST-4X and ST-5 or a 12V, 50VA transformer for the ST-6. 4.3. Connecting to the Computer The ST-4X, ST-5 and ST-6 CCD Cameras are supplied with a 15 foot cable to connect the system to the host computer. The connection is between the CPU's COM connector and the Host Computer's serial COM port. This cable is available in several varieties to support the various host platforms and we try to query users about their systems to insure they receive the correct cable. PC based systems have either a 9 or a 25 pin male D type connector at the rear of the computer for their COM ports. Macintosh computers mostly have a round 8 pin female DIN connector for their Modem and Printer ports. For PC systems we recommend using COM 1 or COM 2 for connecting to the camera. While CCDOPS supports COM 3 and COM 4, often times there are conflicts between these two COM ports and COM 1 and 2. If the cable we supply you does not have the connector that mates with your COM ports then a quick trip to Radio Shack for an adapter will solve the problem. On PC based systems there can also be conflicts between other add-ons and the COM ports: most commonly Modem cards, Scanner cards, and Mice. If you experience communications problems with your CCD camera we recommend starting from zero by removing all possibly conflicting cards from the PC and removing all drivers from your CONFIG.SYS and AUTOEXEC.BAT files, adding these items back one at a time to find the source of the conflict. The other common problem that PC users experience in communicating with the cameras is when running under Windows. Windows can severely limit the speed CCDOPS uses in communicating with the CCD Cameras and we highly recommend you only run CCDOPS from DOS when capturing images. Page 22 Section 4 - Camera Hardware For Macintosh users we recommend connecting the camera to the Modem port . The printer port can be used but you will have to turn off AppleTalk and any Background Printing Modem Printer options you may have enabled. While the serial cables supplied with the cameras run 15 feet, the length can be extended to over 1000 feet if done properly. For Macintosh systems this is merely a matter of obtaining or making a longer cable (refer to the table of COM pinouts in Appendix A). For PC systems the problem is a bit more involved. The serial drivers in PC based computers are RS-232 drivers that are not intended to drive long cables at the high Baud rates used in communicating with the CCD cameras. While these drivers will typically drive 30 to 50 feet of cable they will rarely drive 100 feet. The problem is that the RS-232 drivers will not drive the cable capacitance, a problem that is exacerbated by the requirement to use shielded cable to prevent emissions of radio frequency interference. What we recommend is a two step approach to tackling the problem. Try a simple three-conductor shielded cable if your cable run is less than 100 feet. You may get lucky and be spared the additional expense of a more extensive solution. If you have problems with your longer cable, and you're sure the problems are related to the length of the cable (always try our standard cable first to make sure there isn't some other problem) then we recommend you use a five-conductor shielded cable and an RS-232 to RS-422 converter. RS-422 uses two drivers per signal, driving a pair of wires differentially, and can drive much higher cable capacitances over longer distances. The CPU has RS-422 drivers so you need only get a converter for the PC end of the communications link. For specific information about RS-422 converters refer to Appendix A. 4.4. Connecting the Relay Port to the Telescope The ST-4X, ST-5 and ST-6 camera systems can be used as autoguiders where the telescope's position is periodically corrected for minor variations in the RA and DEC drives. The host software functions as an autoguider in two modes: the Track mode and the Track and Accumulate mode. In the Track mode the host software corrects the telescope as often a once every 2 seconds to compensate for drift in the mount and drive system. The host software and the CCD camera operate in tandem to repeatedly take exposures of the designated guide star, calculate its position to a tenth of a pixel accuracy and then automatically activate the buttons on the telescope's hand controller to move the star right back to its intended position. It does this tirelessly to guide long duration astrophotographs. In the Track and Accumulate mode the software takes a series of images and automatically co-registers and co-adds the images to remove the effects of telescope drift. Typically you would take ten 1 minute "snapshots" to produce an image that is comparable to a single 10 minute exposure except that no guiding is required. The reason no guiding is required is that with most modern telescope mounts the drift over the relatively short 1 minute interval is small enough to preserve round star images, a feat that even the best telescope mounts will not maintain over the longer ten minute interval. The Track and Accumulate software does allow correction of the telescope position in the interval between snapshots to keep the guide star grossly positioned within the field of view, but it is the precise coregistration of images that accounts for the streakless images. Page 23 Section 4 - Camera Hardware The host software and the CCD camera control the telescope through the Relay port on the CPU. By interfacing the CPU to the telescope's hand controller the CPU is able to move the telescope as you would: by effectively closing one of the four switches that slews the telescope. Note: You only need to interface the CPU's Relay port to your telescope if you are planning on using the camera system as an autoguider or feel you need to have the Track and Accumulate command make telescope corrections between images because your drive has a large amount of long term drift. Some recent model telescopes (like the Celestron Ultima and the Meade LX200) have connectors on the drive controller that interface directly to the CPU Relay port. All that's required is a simple cable to attach the CPU's 15 pin Relay port to the telescope's telephone-jack type CCD connector. SBIG offers its TIC (Tracking Interface Cable) for this express purpose although it would take only one-half hour to modify a standard 6-pin telephone cable to interface to the Relay port (see Appendix A for specific pin outs, etc.). Older telescopes generally require modifying the hand controller to accept input from the CPU's Relay port. The difficulty of this task varies with the drive corrector model and we maintain a database of instructions for the more popular telescopes that we will gladly share with you. For a minimal charge will also modify your hand controllers if you feel you do not have the skills necessary to accomplish such a task. In general, the Camera has five internal relays that are used in tracking applications. There is one relay for each of the four correction directions on the hand controller (North, South, East and West) plus an additional relay for an alarm should the CPU be unable to continue guiding for some reason. Each of the relays has a Common, a Normally Open, and a Normally Closed contact. For example, when the relay is inactivated there is a connection between the Common and the Normally Closed contact. When the relay is activated (trying to correct the telescope) the contact is between the Common and the Normally Open contacts. These relay contacts are brought out the CPU's Relay port and the standard cable supplied by SBIG has twelve colored wires with tinned flying leads (see Appendix A for a pinout of the Relay port and the standard Relay Cable) that you solder into your hand controller. If your hand controller is from a relatively recent model telescope it probably has four buttons that have a "push to make" configuration. By "push to make" we mean that the switches have two contacts that are shorted together when the button is pressed. If that's the case then it is a simple matter of soldering the Common and Normally Open leads of the appropriate relay to the corresponding switch, without having to cut any traces, as shown in Figure 4.1 below. B: Modified Push to Make Switch c common A: Unmodified Push to Make Switch relay switch switch nc no normally open Figure 4.1 - Push to Make Switch Modification Another less common type of switch configuration (although it seems to have been used more often in older hand controllers) involve hand controller buttons that use both a push to make Page 24 Section 4 - Camera Hardware contact in conjunction with a push to break contact. The modification required for these switches involves cutting traces or wires in the hand controller. Essentially the CPU relay's Normally Open is wired in parallel with the switch (activating the relay or pushing the hand controller button closes the Normally Open or Push to Make contact) while at the same time the Normally Closed contact is wired in series with the switch (activating the relay or pushing the hand controller button opens the Normally Closed or the Push to Break contact). This type of switch modification is shown in Figure 4.2 below. One caveat about this type of switch configuration is that the CPU must be plugged into the hand controller (although the CPU needn't be powered up) in order for the hand controller to function on its own. This is due to the necessity of keeping the relay's Normally Closed contact intact since as previously mentioned the Relay and the Hand Controller switch are in series. This need for the continued presence of the CPU can be alleviated by making a CPU eliminator as shown in Figure 4.3 to plug into the end of the relay cable. The CPU eliminator essentially makes the four Normally Closed contacts. A: Unmodified Push to Make/Break Switch c common c c B: Modified Push to Make/Break Switch common switch nc no normally open normally closed nc no nc relay no normally open normally closed Figure 4.2- Push to Make/Brake Modification 15 Pin Male D Connector (back view) 1 8 15 9 Figure 4.3 - CPU Eliminator Plug The last type of hand controller that is moderately common is the resistor joystick. In this joystick each axis of the joystick is connected to a potentiometer or variable resistor. Moving the joystick handle left or right rotates a potentiometer, varying the resistance between a central "wiper" contact and the two ends of a fixed resistor. The relays in the CPU can be interfaced to the joystick as shown in Figure 4.4 below. Essentially the relays are used to connect the wire that used to attach to the wiper to either end of the potentiometer when the opposing relays are activated. Page 25 Section 4 - Camera Hardware A + relay A c nc B no C - relay c nc no wiper B C potentiometer A: Unmodified Joystick B: Modified Joystick Figure 4.4 - Joystick Modification A slight variation on the joystick modification is to build a complete joystick eliminator as shown in Figure 4.5 below. The only difference between this and the previous modification is that two fixed resistors per axis are used to simulate the potentiometer at its mid position. You do not need to make modifications to the joystick; you essentially build an unadjustable version. This may be easier than modifying your hand controller if you can trace out the wiring of your joystick to its connector. A + relay c A - relay c nc nc no wiper B C no R potentiometer A: Unmodified Joystick B C R/2 R/2 B: Joystick Eliminator Figure 4.5- Joystick Eliminator 4.5. Modular Family of CCD Cameras With the introduction of the ST-6 CCD Camera in 1992 SBIG started a line of high quality, low noise, modular CCD cameras. This line is being expanded by the introduction of the ST-4X and ST-5. All three of these cameras share a common CPU referred to as the Universal CPU. A single CPU can support the three different cameras through the use of an integrated Optical Head and Readout/Clocking Electronics in the case of the ST-6 or with the separate Optical Head and Readout/Clocking Electronics in the case of the ST-4X and ST-5. The benefits of a modular line of CCD Cameras are many fold. Users can buy as much CCD Camera as they need or can afford, with the assurance that they can upgrade to higher performance systems in the future. With a single CPU supporting all three systems, camera control software like CCDOPS can easily support all three models. This last point assures a wide variety of third party software. Software developers can produce one package for the many users across the model line instead of three different packages for each of the cameras. Page 26 Section 4 - Camera Hardware While the ST-4X, ST-5 and ST-6 have many similarities, there are also important differences between the products. Table 4.2 below highlights the differences from a system's standpoint: Camera ST-4X ST-5 ST-6 A/D Resolution 14 bits 14 bits 16 bits Temperature Regulation Open Loop Closed Loop Closed Loop Electromechanical Vane No No Yes Electronic Shutter None 1 1000 second 1 300 second Table 4.2 - System Features How these features affect the average user are discussed in the paragraphs below: A/D Resolution - This is a rough indication of the camera's dynamic range. Higher precision A/D Converters are able to more finely resolve differences in light levels, or for larger CCDs with greater full well capacities, they are able to handle larger total charges with the same resolution. Temperature Regulation - In an open loop system like the ST-4X the CCD cooling is either turned on or turned off. While this provides for adequate cooling of the CCD, the CCD's temperature is not regulated which makes it important to take dark frames in close proximity to the associated light frame. Closed loop systems like the ST-5 and ST-6 regulate the CCD's temperature to an accuracy of ±0.1° C making using a library of dark frames practical. Electromechanical Vane - Having the vane in the ST-6 means the host software can effectively "cover the telescope" and take dark frames remotely, without the user having to get up and physically cover the telescope. Electronic Shutter - Having an electronic shutter involves having a CCD with a frame transfer region. These CCDs actually have an array that has twice the number of rows advertised, where the bottom half is open to the light (referred to as the Image Area), and the top half is covered with a metalization layer (referred to as the Storage Area). In frame transfer CCDs at the end of the exposure, the pixel data from the Image Area is transferred into the Storage Area very rapidly where it can be read out with a minimum of streaking. In addition to the system level differences between the ST-4X, ST-5 and ST-6, Table 4.3 below highlights the differences owing to the different CCDs used in the cameras: Camera ST-4X ST-5 ST-6 CCD Used TC-211 TC-255 TC-241 Number of Pixels 192 x 164 320 x 240 375 x 242 Pixel Dims. 13.75 x 16µ 10 x 10µ 23 x 27µ Array Dimension 2.6 x 2.6mm 3.2 x 2.4mm 6.6 x 8.8mm Read Noise 22e- rms 20e- rms 30e- rms Full Well Capacity 150Ke50Ke400Ke- Table 4.3- CCD Differences How these various specifications affect the average user is described in the following paragraphs: Number of Pixels - The number of pixels in the CCD affects the resolution of the final images. The highest resolution device is best but it does not come without cost. Larger CCDs cost more money and drive the system costs up. They are harder to cool, Page 27 Section 4 - Camera Hardware require more memory to store images, take longer to readout, etc. With PCs and Macintosh computers offering graphics resolutions of 320 x 200 to 640 x 480 with good grey scale, the CCDs used in the ST-4X, ST-5 and ST-6 offer a good trade off between cost and resolution, matching the computer's capabilities well. Pixel Dimensions - The size of the individual pixels themselves really plays into the user's selection of the system focal length. Smaller pixels and smaller CCDs require shorter focal length telescopes to give the same field of view that larger CCDs have with longer focal length telescopes. Smaller pixels can give images with higher spatial resolution up to a point. When the pixel dimensions (in arcseconds of field of view) get smaller than roughly half the seeing, decreasing the pixel size is essentially throwing away resolution. Another aspect of small pixels is that they have smaller full well capacities. For your reference, if you want to determine the field of view for a pixel or entire CCD sensor you can use the following formula: Field of view (arcseconds) = 8120 x size (mm) focal length (inches) where size is the pixel dimension or CCD dimension in millimeters and the focal length is the focal length of the telescope or lens in inches. Also remember that 1° = 3600 arcseconds. Read Noise - The readout noise of a CCD camera affects the graininess of short exposure images. For example, a CCD camera with a readout noise of 30 electrons will give images of objects producing 100 photoelectrons (very dim!) with a Signal to Noise (S/N) of approximately 3 whereas a perfect camera with no readout noise would give a Signal to Noise of 10. Again, this is only important for short exposures or extremely dim objects. As the exposure is increased you rapidly get into a region where the signal to noise of the final image is due solely to the exposure interval. In the previous example increasing the exposure to 1000 photoelectrons results in a S/N of roughly 20 on the camera with 30 electrons readout noise and a S/N of 30 on the noiseless camera. It is also important to note that with the SBIG CCD cameras the noise due to the sky background will exceed the readout noise in 15 to 60 seconds on the typical amateur telescopes. Even the $30,000 priced CCD cameras with 10 electrons of readout noise will not produce a better image after a minute of exposure! Full Well Capacity - The full well capacity of the CCD is the number of electrons each pixel can hold before it starts to loose charge or bleed into adjacent pixels. Larger pixels hold more electrons. This gives an indication of the dynamic range the camera is capable of when compared to the readout noise, but for most astronomers this figure of merit is not all that important. You will rarely takes images that fill the pixels to the maximum level except for stars in the field of view. Low level nebulosity will almost always be well below saturation. While integrating longer would cause more build up of charge, the signal to noise of images like these is proportional to the square-root of the total number of electrons. To get twice the signal to noise you would have to increase the exposure 4 times. An ST-5 with its relatively low full well capacity of 50,000e- could produce an image with a S/N in excess of 200! Antiblooming - All the SBIG CCD cameras have antiblooming protection. Blooming is a phenomena that occurs when pixels fill up. As charge continues to be generated in a full pixel, it has to go somewhere. In CCDs without antiblooming protection the charge spills into neighboring pixels, causing bright streaks in the image. Page 28 Section 4 - Camera Hardware With the CCDs used in the SBIG cameras the excess charge can be drained off saturated pixels by applying clocking to the CCD during integration. This protection allows overexposures of 100-fold without blooming. From the telescope's point of view, the different models offer differing fields of view for a given focal length, or turned around, to achieve the same field of view the different models require differing focal lengths. Tables 4.4 and 4.5 below compare the fields of view for the cameras at several focal lengths, and vice and versa. C8, 8" f/10 LX200, 10" f/35 Field of Pixel Field of Pixel View Size View Size (arcmins) (arcsecs) (arcmins) (arcsecs) 4.2x4.2 1.3x1.5 11.7x11.7 3.7x4.3 5.4x4.1 1.0x1.0 14.4x10.8 2.7x2.7 14.6x11.1 2.3x2.7 38.9x29.5 6.2x7.3 Table 4.4 - Field of View Focal Length to fill ST-4X/ST-5 275mm = 11 inches 13000mm = 510 inches 1040mm = 41 inches " 14" f/11 Field of Pixel View Size (arcmins) (arcsecs) 2.3x2.3 0.7x0.8 2.8x2.1 0.5x0.5 7.6x5.7 1.2x1.4 Camera ST-4X ST-5 ST-6 Object Moon Jupiter M51-Whirlpool Galaxy M27-Dumbell Nebula M57-Ring Nebula Size 0.5° 40 arcseconds 8x5 arcminutes 8.5 x 5.5 arcminutes Focal Length to fill ST-6 760mm = 30 inches 34000mm = 1350 inches 3700mm = 145 inches " 23000mm = 900 inches 1.3 x 1 6400mm = arcminutes 250 inches Table 4.5 - Focal Length Required From these numbers you can deduce that the popular C8, an 8" f/10 telescope will nicely frame the ST-6 for many popular objects whereas a much shorter system (f/3, perhaps achieved with a focal reducer) will frame the same objects for an ST-4X or ST-5. Another point to bear in mind is that, except for planetary images, you'll rarely take images where the pixel size in seconds of arc is down near the seeing limit. Most objects are relatively large, where the field of view is more important than whether the individual pixels are less than half the seeing. 5 f/6.3 with the Meade star digonal focal reducer. Page 29 Section 5 - Camera Software Reference 5. Camera Software Reference This section contains detailed information about CCDOPS, the host computer software for the ST-4X, ST-5 and ST-6 CCD Cameras. While section 5.1 contains information of a general nature, section 5.2 is a very detailed explanation of every command available in CCDOPS, and is organized more as a software reference rather than a narrative to be read from top to bottom. 5.1. Different Host Computers Santa Barbara Instrument Group offers CCDOPS for both IBM PCs/Compatibles and Macintosh computers. The CCDOPS software package supports all three cameras and is designed to be 95% operationally identical on the two different platforms. Images captured on the IBM PC can be used on the Macintosh and vice versa (see Appendix D for more information on Cross Platform Compatibility). The differences between the PC and Macintosh versions of the software are very minor, mostly owing to minor differences in hardware capabilities between the two platforms. Both environments are menu based with full support for the mouse. 5.1.1. Installing the Software The CCDOPS software is provided on floppy diskette, and should be copied to your system's hard disk prior to use. Copy all the files to a directory or folder on your hard disk by following the instructions below: IBM PC Users 1. Insert the 3 or 5 1 2 1 inch diskette into the floppy disk drive. 4 2. At the MS-DOS prompt type "CD \" then hit the Enter key to log into the root directory of your hard disk. 3. Type "MKDIR CCDOPS" then hit the Enter key to create a directory for the software. 4. Type "CD CCDOPS" then hit the Enter key to make that directory active. 5. Type "COPY A:*.*" or "COPY B:*.*" depending on which floppy drive you are using then hit Enter to copy all the software to the CCDOPS directory on your hard disk. When you want to run the software, turn on your computer and type in the following sequence of commands at the MS-DOS prompt: CD \CCDOPS CCDOPS Note: We strongly advise that you do not take images from within Windows or else your ability to communicate with the camera at high speeds may be severely limited. Macintosh Users 1. Insert the 3 inch diskette into the floppy disk drive. 2. Create a new folder on your hard disk named CCDOPS. 3. Click and drag all the files on the CCDOPS diskette into the folder you've just created. After you have finished installing the software place the floppy disk in a safe place in case you need to reinstall it later. 1 2 Page 31 Section 5 - Camera Software Reference 5.1.2. The CCDOPS User Interface The CCDOPS environment presents the user with a user-friendly menu based interface. Rather than having to remember long command names and do a lot of typing, CCDOPS presents all the commands in a logically organized menu structure. The software has been designed to be simple for inexperienced users while offering advanced capabilities as experience grows. As previously stated, many man-hours and much improvement from user's comments and suggestions have gone into the development of CCDOPS. We encourage users to continue to help us improve the software through your comments. At the top of the screen is a menu bar with pull-down menus of logically grouped commands. For example the Camera Menu has commands that allow you to take an image (the Grab Command), focus the camera (the Focus Command) or try to initiate communications with the CCD Camera (the Establish COM Link command). The PC and Macintosh menu bars are shown with one of the pull-down menus in Figure 5.1 below: * File Camera Display Utility Alt-O Alt-S Misc Track FiLter Open... Save... Save Track List... Delete Create Directory... Set Path/Filter... EXit PC Menu Bar Alt-X File Edit Camera Display Utility Misc Track Filter Grab... Focus... Setup... Auto Offset Adjust Manual Offset Adjust Establish COM Link Upload Dark Frame... G F Macintosh Menu Bar Figure 5.1 - CCDOPS Menu Bar Some of the menu commands operate immediately like the Establish COM Link command in the Camera menu. Other commands require further user input such as the Grab command. These "further input required" commands are shown with an ellipsis (...) after the command name. Also, some often used commands have a "hot-key" associated with them which is shown in the menu. Typing the hot-key combination invokes the command. For example holding down the key on the Macintosh or the Alt key on the PC and then hitting the G key invokes the Grab Command. Page 32 Section 5 - Camera Software Reference At the bottom of the screen is the Status Window. The Status Window, shown in Figure 5.2 below, contains two or three sections. The top section called the Status Box is used by the software to provide written feedback to the user about the activities being performed. On the PC version of CCDOPS, there is a double-outlined Data Buffer Box below the Status Box that tells the user about the status of image data held in the software's image buffer. The type of camera used to take the image and the name of the image are shown as well as an indication of whether the image has been saved on the disk drive. Also shown is the status of the Color Tables indicating whether any custom color tables have been loaded. Color Tables are used in conjunction with the Display Command to assign different colors to the display of images rather than the typical grey scale. Status Taking light exposure... Grab complete. Data Buffer Name:No data present Camera Link:[ST-5]COM1:115K Res:High Saved:- Color Tables:---- Setpoint:-20.00Temperature:-19.75 ( 75%) Reuse Darks:No Filter:Red PC Status Window Macintosh Status Window Figure 5.2- Status Window At the very bottom of the Status Window is the double outlined Camera Box that indicates the status of any CCD camera attached to the host computer through one of its COM ports. The Link status shows the type of camera and the COM port and Baud Rate used to communicate with the camera. Also shown (if a camera is attached) is the status of the camera's cooling. For ST-4X cameras the cooling is either turned on and Enabled or is Off. For ST-5 and ST-6 cameras the user selectable setpoint temperature and the camera's actual temperature are shown as well as the percentage of power being applied to the TE cooler to maintain that setpoint. The second line of the Camera Box shows the resolution mode the camera is setup for (using the Camera Setup command) and whether dark frames will be reused. In the lower right hand corner the active optical filter from the filter wheel is shown. 6 The region between the menu bar and the status window is called the Desktop. The CCDOPS software uses the Desktop area to get further user input for commands like the Grab Command using data entry boxes called Dialogs (or Dialog Boxes). The Desktop area is also to inform the user about the progress of activities that take a long time, such as taking a 1 minute exposure, and to warn the user about important aspects regarding the operation of the camera. 6 CCDOPS supports the motorized and manual CFW6 filter wheels. Commands in the Filter menu are used to position the motorized filter wheel or inform the software about the position of the manual filter wheel. Page 33 Section 5 - Camera Software Reference Dialog Boxes pop-up on the Desktop and present the user with a series of data entry items, which as stated previously, fine tune the operation of certain commands. Within these dialogs, data entry items are arranged in a vertical fashion. The user proceeds through each item, setting it as appropriate. Figure 5.3 below shows the PC and Macintosh versions of the dialog box for the Grab Command: Grab Exposure time (0.01-3600): Dark Frame: Auto display: Auto contrast: Background (0-65535): Range (16-65536): Exposure delay(0-99): Auto Grab: 30.00 None Also Yes No Yes No 0 1000 0 Yes No [ Only [ Enter ] PC Grab Dialog Esc ] Macintosh Grab Dialog Figure 5.3 - Grab Dialog The Grab Dialog is a good example because it shows the two major types of items commonly found in dialog boxes: list items and data entry items. List items are like the Dark Frame item shown above where the user selects one setting from a list of settings. Data entry items like the Exposure time require the user to type in a value. 5.1.3. CCDOPS for IBM PCs The PC version of CCDOPS runs under DOS but provides a very user friendly environment. Even though it is not Windows software, the user interface is menu based and supports a broad range of hardware configurations. Running under DOS assures the maximum compatibility with the PC systems users currently have and operate. In the PC environment the CCDOPS software works in two modes: Command Mode and Graphics Mode. The command mode is used to interact with the user and to control the Page 34 Section 5 - Camera Software Reference acquisition and processing of images. The Graphics Mode (discussed further below) is used when image display is required. Command Mode Along the top of the Command Mode screen is a menu bar with its pull-down menus (shown in the top of Figure 5.1). Pulling down menus and executing commands can be done using the keyboard or the mouse. Using the mouse is quite easy: you simply click the mouse button on the menu title to pull down the menu and then click the mouse again on the desired menu command. Using the keyboard is almost as intuitive: you simply select the menu by using the left and right arrow keys, and then select the menu command using the up and down arrow keys, executing the command by hitting the Enter key once the appropriate command has been selected. You also perform data entry in Dialog Boxes using the keyboard and the mouse. Using the keyboard you select the item to change using the up and down arrow keys and then changed the item by typing in the desired value or by using the left and right arrow keys for list items. You can also use the Tab key to tab down through the items in a dialog or you can click the mouse on an item to move to that item or click in one of the options in a list item to select that option. At the bottom of all dialog boxes are two buttons: Enter and Esc. Clicking the mouse on the Enter button or hitting the Enter key causes the command to read all the data entry back from the dialog and finish executing the command. Clicking the Esc button or hitting the Esc key aborts the command. Advanced Tips · Each item in a dialog can be accessed though hot-keys. By holding down the Alt key while hitting the key shown in red or highlighted you can move directly to that item. For example hitting Alt E moves to the Exposure time item in the Grab Dialog shown above. In list items options can be selected by hitting the first letter of the option. For example, hitting Y will select the Yes option if you are in the Auto display item of the Grab Dialog. In data entry items the first key hit erases the entire contents of the data entry item unless you hit the Backspace key or the left or right arrow keys described below. In data entry items the Backspace key erases one character and the left and right arrow keys move the cursor within the data entry allowing correction or insertion. In the data entry items hitting the Delete or Del keys erase the entire contents of the data entry item. · · · · Graphics Mode In the PC version of CCDOPS the software switches to Graphics Mode when the image needs to be displayed. Graphics mode is used for the Display Command in the Image Menu as well as the Focus and Track and Accumulate modes. These modes all display the image in the upperright corner of the display with an optional pull-down menu in the upper-left corner of the display. Page 35 Section 5 - Camera Software Reference The size of the image and the "quality" of the image depends largely on the type of graphics adapter you have in your computer. VGA and/or Super VGA7 are highly recommended in all cases except where you have dual systems: one portable system that you take into the field to acquire images which can have less than VGA capabilities and a second system for display and image processing. With VGA displays the images can be shown using 64 shades of grey. This produces very nice looking images. EGA based systems are also supported. With an EGA color display the images are "ok" but do not offer much latitude in terms of grey scales or brightness variations. An EGA display adapter with a monochrome monitor works fairly well, again supporting 64 shades of grey but it's not nearly as flexible as VGA based systems. At the very bottom of the ladder are systems based upon CGA graphics. These systems have very poor spatial and color resolution and produce "blocky" looking images. Our intention in supporting CGA systems was to allow older laptop computers to be used in the field for acquisition of images. Users will not be happy with the quality of displayed images for any serious image processing and are strongly encouraged to upgrade to VGA based systems. In Graphics Mode data entry is minimal, restricted mainly to selecting items from pulldown menus. As previously mentioned, many of the graphics mode displays have a pull-down menu. The menu is indicated by the presence of a menu name in a rectangular box in the upper-left corner of the display as shown in Figure 5.4 below. Accessing items in the menu is easily achieved using the mouse or the keyboard. Display X-Hairs H-Flip V-Flip Zoom Crop Smoothing Negative Quit Figure 5.4 - Graphics Mode Menu Using the mouse is identical to that in the Command Mode: you click on the menu title to reveal the pull-down menu and then click again on the command you wish to execute. Using the keyboard is also similar to Command Mode: you hit the Enter or Down Arrow keys to pulldown the menu, select the appropriate item using the up and down arrow keys, and then hit the Enter key again to execute the command. The items also have "hot-keys" associated with them that will make it quicker as you gain experience with the software. Hitting the first letter of the command name will execute the command without having to pull down the menu. As an example, hitting the "X" key would execute the "X-Hairs" command in the menu shown above. 7 CCDOPS for the PC supports VESA compliant and Paradise and Tseng 4000 based Super VGA cards where images are displayed in the 640x480 or 640x400 pixel modes with 256 colors. Page 36 Section 5 - Camera Software Reference Note: You do not have to hold down the Alt key to access the hot-keys in the Graphics Mode. When you are through with the command you are using that invoked the Graphics Mode hit the Esc key to return CCDOPS to the Command Mode. 5.1.4. CCDOPS on Macintosh Computers The Macintosh version of CCDOPS takes full advantage of the graphical user interface (GUI) built into the Macintosh System Software. This is the ideal environment for imaging applications like CCDOPS since the software has simultaneous access to menus and dialogs for controlling the camera as well as high level graphics for displaying the images. Any Macintosh user also has the benefit of Apple's enormous investment in the area of user interfaces. Software packages for the Macintosh share the common "toolbox" which makes learning to operate the Macintosh a one-time event. All software packages share the same look and feel. If you know how to use MacWrite you're right at home with other packages, including CCDOPS. Any Macintosh user will freely admit that he or she "hardly ever reads the manual". While the PC and Macintosh versions of CCDOPS provide virtually the same level of capabilities there are minor differences between the two programs owing largely to differences in the operating system. Where as the PC CCDOPS must switch between Command Mode and Graphics Mode, CCDOPS for the Macintosh offers both capabilities simultaneously. CCDOPS for the Macintosh also takes advantage of the "complete system" approach that the Macintosh offers allowing customization of color tables, printing of images and cutting and pasting. If you are a new user to the Macintosh and CCDOPS is your first program we ask you to spend the time with the training disks that Apple has provided you in learning to use the system. It is a small investment in time that will pay off for years. 5.2. CCDOPS Menus and Commands This section has detailed descriptions about the Menus and their respective Commands. For each Menu, a brief description of each Command is given. For Commands that require a lot of user input or explanation, a separate description is included. 5.2.1. Command Tree The following figure is a Command Tree of each of the Menus and Commands available in CCDOPS. Page 37 Section 5 - Camera Software Reference Page 38 Section 5 - Camera Software Reference 5.2.2. File Menu on the Macintosh Purpose:The commands in the File menu allow loading and saving images on disk. Commands Open Close This command loads ST-4X, ST-5 or ST-6 image files from disk into memory where they can be displayed or processed. Closes the image in memory by purging it from memory. If the image has changed and has not been saved you are given the opportunity to save it before closing it. Note that you must close one image before you can open another. Saves the image held in memory on the disk. The same name used to load the file or last save it is used. You also use this command to save Track Lists produced by the Track and Accumulate command by activating the Track List window and invoking this command. Saves the image held in memory on the disk, giving you the opportunity to rename the image or save it in the folder of your choice. You can also choose to save the image using the Compressed, Uncompressed, FITS or TIFF formats. Discards any changes made to the image in memory since the last save by reloading the image from disk. Allows you to select the orientation and other page setup options when printing images. We suggest using the Portrait orientation and turning off the Graphics Smoothing and Faster Bitmap Printing options. Prints the image as it is displayed in the Picture window. If your printer does not support grey-scale you should first set the Graphics mode item in the Mac Setup command to one of the two color modes. Quits CCDOPS back to the Finder. Save Save As Revert to Saved Page Setup Print Quit Notes · The Compressed and Uncompressed image formats are SBIG native formats. You can typically use 30% to 50% less disk space by using the Compressed format. · The TIFF format is supported by third party graphics processing programs and allows you to export CCD images to those other programs. · The FITS format is supported by third party astronomical image processing programs and allows you to export CCD images to those programs. · In addition to printing images, you can make a copy of the image displayed in the Picture window by making that window active and then using the Copy command in the Edit menu. · When printing grey scale images remember to select the Color/Greyscale Print option in the Print dialog. See Also: Mac Setup Command, Save FITS Command, Save TIFF Command Page 39 Section 5 - Camera Software Reference 5.2.3. File Menu on the PC Purpose:The commands in the File menu allow loading and saving images on disk. Commands Open Save This command loads ST-4X, ST-5 or ST-6 image files from disk into memory where they can be displayed or processed. This command saves the image in memory onto the disk. You are asked for the name to use in saving the file, and if that name would overwrite an existing image you are warned. You can save the image using the Compressed, Uncompressed, FITS or TIFF formats. Use this command to save the Track List produced by the Track and Accumulate command if you plan on flat fielding your images. This command allows you to delete files on the disk to free up space without having to exit to DOS. The files that match the Filter in the Path from the Set Path/Filter Command are shown. This command allows you to create a new directory in which to store images without having to exit to DOS. You enter the path and name of the directory to create and you can also make the newly created directory the current Path. This command allows you to set the Path where CCDOPS looks for image files to load and save and the Filter which allows only files matching the filter to be shown in the Load Image command. This command quits CCDOPS back to DOS. If there is unsaved image data or the camera's temperature regulation is active you are given the chance to not exit. Save Track List Delete Create Directory Set Path/Filter Exit Notes · The Compressed and Uncompressed image formats are SBIG native formats. You can typically use 30% to 50% less disk space by using the Compressed format. · The TIFF format is supported by third party graphics processing programs and allows you to export CCD images to those other programs. · The FITS format is supported by third party astronomical image processing programs and allows you to export CCD images to those programs. · In the Open and Delete commands, clicking on the [ Info? ] button or hitting the Space bar shows the Image Parameters associated with the currently highlighted file. · The Path is the drive and directory where CCDOPS tries to open and save images. For example setting the Path to "C:\ST-6\DEEPSKY" (without the quotes) causes CCDOPS to look in the DEEPSKY subdirectory of the ST-6 directory on hard drive C:. To set the Path to the directory where CCDOPS resides erase the Path or set it to ".\" (do not type the quotes). · The Filter is used by the Open and Delete commands to select files to show in the directory listing. Only files matching the Filter are shown. For example, setting the Filter to "*.ST6" shows all files with the ST6 extension. To show all files set the Filter to "*.*" (once again, do not type the quotes). · If more than 40 files are available in the Open and Delete commands then you can use the PgDn and PgUp keys to see 40 files at a time. See Also: Save FITS Command, Save TIFF Command Page 40 Section 5 - Camera Software Reference Save FITS Command File Menu, Save Command Purpose: The Save FITS Command is used to save the image in memory on disk using the FITS format. You access this command through the Save command by selecting FITS format. Dialog Parameters Bits per pixel Set this item according to the precision required in the FITS file. For 16 bit FITS files the 16 bit image data is saved unchanged. For 8 bit FITS files the 16 bit image is scaled using the Back and Range parameters. Back/Range For 8 bit FITS files these parameters control the scaling of the 16 bit image data to the 8 bit FITS file data. Pixels below the Back value are written as zero. Pixels above Back + Range are written as 255. Pixels between Back and Back + Range are scaled linearly from 0 to 255. Object Set this item to any text you want to attach to the FITS file describing the object imaged. Date of Obs. This item gets set to the date the FITS file is being saved and can be changed. Institution Set this item to any text you want to attach to the FITS file describing the institution that imaged the object. Telescope Set this item to any text you want to attach to the FITS file describing the telescope that imaged the object. Observer Set this item to any text you want to attach to the FITS file describing the observer that imaged the object. This data is initialized from the Telescope Setup command. Comment Set this item to any text you want to attach to the FITS file as a comment. This is initialized to the Note attached to the image with the Edit Parameters command, but can be overridden. Notes · Only 8 bit FITS files use the Back and Range parameters to scale the image data. 16 bit FITS files are written directly from the image pixel values. · Prior to saving 8 bit FITS files you may wish to display the image to find the appropriate settings for the Back and Range parameters. As a convenience the settings from the Display Image command are automatically copied to the Back and Range parameters in this command, but they can be overridden, of course. See Also: Display Image Command, Edit Parameters Command Page 41 Section 5 - Camera Software Reference Save TIFF Command File Menu, Save Command Purpose: The Save TIFF Command is used to save the image in memory on disk using the TIFF format. You access this command through the Save command by selecting TIFF format. Dialog Parameters Bits per pixel Set this item according to the precision required in the TIFF file. For 16 bit TIFF files the 16 bit image data is saved unchanged. For 8 bit TIFF files the 16 bit image is scaled using the Back and Range parameters. Back/Range For 8 bit TIFF files these parameters control the scaling of the 16 bit image data to the 8 bit TIFF file data. Pixels below the Back value are written as zero. Pixels above Back + Range are written as 255. Pixels between Back and Back + Range are scaled linearly from 0 to 255. Strips You will typically want to set this item to Multiple as most TIFF readers are capable of reading that format. The Single setting can be used if your TIFF reader will not read TIFF files created with the Multiple setting. Observer Set this item to any text you want to attach to the TIFF file describing the observer that imaged the object. This data is initialized from the Telescope Setup command. Comment Set this item to any text you want to attach to the TIFF file as a comment. This is initialized to the Note attached to the image with the Edit Parameters command, but can be overridden. Notes · Only 8 bit TIFF files use the Back and Range parameters to scale the image data. 16 bit TIFF files are written directly from the image pixel values. · Prior to saving 8 bit TIFF files you may wish to display the image to find the appropriate settings for the Back and Range parameters. As a convenience the settings from the Display Image command are automatically copied to the Back and Range parameters in this command. See Also: Display Image Command, Edit Parameters Command. Page 42 Section 5 - Camera Software Reference 5.2.4. Edit Menu on the Macintosh Purpose:The commands in the Edit menu are the standard edit commands for the Macintosh plus an additional command for the Icon Bar. Commands Undo Cut Copy This command is used with desk accessories. This command is used with desk accessories. This command is used with desk accessories or when the Picture Window is active to make a copy of the image displayed onto the Clipboard where it can be pasted into the Scrapbook or other application. This command is used with desk accessories. This command makes the Icon Bar visible or invisible. Paste Show/Hide Icon Bar Notes · The Icon Bar is a small window with icons in it for Grab, Focus, Track, Track and Accumulate, Save and Open. Clicking on one of these icons is a shortcut for the pulling down the menu and invoking the respective commands. Page 43 Section 5 - Camera Software Reference 5.2.5. Camera Menu Purpose: The commands in the Camera menu are used to control the camera for taking images, focusing, etc. Grab This command is used to take a single image or a sequence of images and log them to disk (Auto Grab Command). Typically you would use this command once the object is focused and centered in the field of view and you're ready to take the "keeper" image. This command is used to focus the CCD camera or to center objects in the field of view as it repeatedly takes images and displays them. This command is used to configure the CCD camera hardware for subsequent images. Items include the temperature regulation, resolution, etc. For ST-6 cameras this command automatically adjusts the head offset by closing the vane and measuring the video black level, adjusting the offset until the black level is between 2,000 and 10,000 counts. For ST-6 cameras this command allows the user to manually adjust the head offset. For the ST-4X and ST-5 the head offset is not adjustable although this command can be used to measure the black level. If you choose to use this command you should adjust the ST-6's offset using the cursor keys until the Video reads between 2,000 and 10,000 counts. This command tries to establish a communications link with an ST-4X, ST-5 or ST-6 attached to the serial COM port. The desired COM port and Baud rate are set using the Mac Setup or PC Setup commands in the Misc menu. Once a communications link is established, the Status Window is updated to show the active COM port and Baud rate. This command allows you to select a previously taken and saved dark image and upload it to the camera. That dark frame can be reused in subsequent images if the Reuse Dark Frames item in the Camera Setup command is enabled. Commands Focus Setup Auto Offset Adjust (ST-6 Only) Manual Offset Adjust Establish COM Link Upload Dark Frame Notes · For a dark frame to be reusable it must match the current imaging mode parameters including the resolution, frame size, exposure duration, temperature, etc. See Also: Grab Command, Auto Grab Command, Focus Command, Camera Setup Commands, Mac Setup Command, PC Setup Command Page 44 Section 5 - Camera Software Reference Grab Command Camera Menu Purpose: The Grab Command is used to take a single exposure or a series of exposures and log them to the disk (Auto Grab Command). Dialog Parameters Exposure time Set this item to the desired exposure duration in increments of a hundredth of a second. Dark frame Set this item to Only to take and download a single dark frame. Set the item to Also to take a dark frame followed by a light frame and download the difference. Set this item to None to take and download a single light frame. Image size Set this item to Full to take an image using the CCD's full field of view. The Half and Quarter settings take an image using the central 11 11 x or x 22 44 Auto display (PC Only) Auto contrast (PC Only) Background Range (PC Only) Exposure delay Auto Grab field of view, reducing the memory requirements accordingly. On the ST4X the Half setting takes a Half Frame image where the lower half of the CCD, at full width, is used to reduce streaking. The image is automatically displayed after being downloaded if this item is set to Yes. Note: On the Macintosh the image is always displayed after being downloaded. When the Auto Display item is set to Yes , setting this item to Yes causes the image to be displayed using Auto Contrast. Note: On the Macintosh Auto Contrast is used if the Auto check-box is selected in the Contrast Window. These items affect the contrast of the displayed image if the Auto Display item is set Yes and the Auto Contrast item is set No. Note: On the Macintosh the Back and Range parameters from the Contrast Window are used. Setting this item to any value except zero causes the software to delay that number of seconds before taking the light image. This allows the user to start guiding or turn off the lights, for example. Setting this item to Yes invokes the Auto Grab command which allows taking a sequence of images and logging them to disk at a regular interval. Notes · When taking a dark frame with the ST-4X and ST-5 the user is asked to cover the telescope. · If the Camera Setup has the Reuse Dark Frames item set Yes the Grab Command will try to reuse any dark frames stored in the Camera. This can increase throughput significantly if you plan on taking several images with the same exposure time. · If you get serial "Time Out" errors while the image is being downloaded you should decrease the Baud rate one step using the PC or Mac Setup command. · Hit the Esc key on the PC or hit -Period on the Macintosh to abort an image in progress. See Also: Auto Grab Command, Display Image Command, Camera Setup Commands, PC Setup Command, Mac Setup Command, Macintosh Contrast Window Page 45 Section 5 - Camera Software Reference Auto Grab Command Camera Menu, Grab Command Purpose: The Auto Grab Command is used to take a sequence of images at a periodic interval and log them to disk. Dialog Parameters File name Set this item to the name you want the Auto Grab command to use when saving the files. For Macintosh users you enter the name and select the destination folder using the Standard File Save dialog. For PC users you can enter up to 5 characters for the file name plus a three character extension, for example ORION.FTS. In both cases the Auto Grab command appends "NNN" to the file name as the images are saved where NNN is the image sequence number from 001 to 999 . In the example above the names would be ORION001.FTS, ORION002.FTS, etc. Type Set this item to the type of file you want saved for each image. The Uncompressed and Compressed formats are SBIG native formats which can be read back in and processed by CCDOPS. The TIFF and FITS formats are supported by other software packages but you will not be to load images saved in these formats back into CCDOPS. No. of Exp. Set this item to the number of images you wish to grab and log to disk. Exp. interval Set this item to the interval from start of image to start of image. For example, setting this item to 120 causes the Auto Grab command to start a new image every 2 minutes. Dark interval Set this item to the number of images to take before taking a new dark frame. If this item is set to Series then a single dark frame is taken at the start for the entire series of images. Notes · There is a lower limit to the setting of the Exposure Interval item which is the amount of time required to expose, digitize, download, and save the image. Setting the Exposure Interval below that value will result in the Auto Grab command taking images as fast as it can. · When higher image throughput is required the amount of time required to digitize, download and save the image can be reduced by lowering the camera resolution in the Camera Setup command or by limiting the field of view with the Image size item in the Grab Command. · You should set the Image Size item in the Grab Command to the smallest size that will encompass the object to save time and disk space. For example if you're monitoring stellar brightness then you should center the object and reduce the Image size to Half or Quarter. See Also: Camera Setup Commands, Grab Command Page 46 Section 5 - Camera Software Reference Focus Command Camera Menu Purpose: The Focus Command is used to focus the CCD camera or to center objects in the field of view. It repeatedly acquires and displays images. Dialog Parameters Exposure time Set this item to the desired exposure duration in increments of a hundredth of a second. Auto contrast Setting this item to Yes causes the image to be displayed using Auto (PC Only) Contrast where CCDOPS sets the Background and Range parameters based upon the image data. This works well for most images although when focusing on stars you may often find disabling Auto contrast a better option so you can set the Range to show the star's profile. Note: On the Macintosh Auto Contrast is used if the Auto check-box is selected in the Contrast Window. Background These items affect the contrast of the displayed image if the Auto Range Contrast item is set No. (PC Only) Note: On the Macintosh the Back and Range parameters from the Contrast Window are used. Frame size With this item set to Full you capture images using the CCD's entire field of view. In the Planet mode, a full image is captured and then you select a sub-area of the CCD's field of view for subsequent images. In the Spot mode the camera digitizes the CCD's entire field of view but only downloads and displays a small region of pixels surrounding the brightest pixel. In Dim mode the camera digitizes the CCD's entire field of view and then reduces the image by combining pixels for download and display. Update mode Set this item to Manual to have the software pause between images to give you time to inspect the image or adjust the telescope before the next exposure is started. Readout type Set this item to Rapid Readout to double the image digitization rate (ST-6 Only) (increasing throughput) at the cost of increased line-to-line noise in the image. This could be used when focusing on bright stars (over 1000 counts) or when centering objects. You should use the Low Noise setting when you are taking images you want to save. Notes · Focus mode takes a dark image at the start of the process. With a ST-6 this is automatic. With a ST-4X or ST-5 you are asked to cover the telescope. If you're taking short exposures with these cameras (less than 3 seconds) you can skip the dark frame by hitting the Esc key. · Planet mode is most useful for fine focusing as the image throughput is increased due to the relatively small number of pixels involved. You would not want to use Dim mode or reduced resolution modes from the Camera Setup command to achieve focus since those options increase the pixel size, making it impossible to get a better focus than the pixel size. · Dim mode is most useful for centering objects or locating dim objects. It maintains the full field of view with larger pixels (reduced resolution) resulting in increased throughput and increased sensitivity to dim, diffuse objects. · The Auto setting of the Resolution item in the Camera Setup mode is intended for Focus mode. It automatically switches between Low resolution in Full mode where you gain increased throughput and High resolution in Planet mode for critical focusing. A subsequent Gran command will be in th full resolution mode.