G2 CCD Operating Manual
Version 2.3 Modified on November 26th, 2009 All information furnished by Moravian Instruments is believed to be accurate. Moravian Instruments reserves the right to change any information contained herein without notice. G2 CCD devices are not authorized for and should not be used within Life Support Systems without the specific written consent of the Moravian Instruments.
Table of Contents Introduction....................................................................................................5 Camera Technical Specifications...................................................................7 CCD Chip...............................................................................................10 Model G2-0402.................................................................................11 Model G2-1600................................................................
First Images............................................................................................36 Brightness and Contrast – Image Stretching..........................................37 Calibration..............................................................................................38 Color Images with monochrome camera and filters...............................40 Color images with color camera.............................................................42 Balancing colors...................
Introduction Thank you for choosing the G2 CCD camera. The cooled, slow-scan series of G2 CCD cameras were developed for imaging under extremely low-light conditions in astronomy, microscopy and similar areas. The development team focused to every detail of camera mechanics, cooling, electronics and software to create state-of-the-art product. G2 CCD cameras feature compact and robust construction, rich features, sophisticated software support and easy operation.
to the host PC. Although G2 CCD cameras can operate through a USB hub, it can negatively affect the camera performance, like download time etc. It is recommended to connect other USB devices through USB hub (e.g. the mouse) and to provide the camera a direct USB connection to the host PC. The G2 CCD camera needs an external power supply to operate. It is not possible to run the camera from the power lines provided by the USB cable, which is common for webcams or very simple imagers.
Camera Technical Specifications G2 series of CCD cameras are manufactured with two kinds of CCD detectors: ● G2 cameras with Kodak KAF (Full Frame – FF) CCD architecture. Almost all Full Frame CCD detector area is exposed to light. This is why these detectors provide very high quantum efficiency.
● G2 cameras with Kodak KAI (Interline Transfer – IT) architecture. There is a shielded column of pixels just beside each column of active pixels on these detectors. The shielded columns are called Vertical registers. One pulse moves charge from exposed pixels to shielded pixels on the end of each exposure. The the charge is moved from vertical registers to horizontal register and digitized in the same way like in the case of Full Frame detectors.
G2 camera models with Full Frame CCD detectors: Model G2-0402 G2-1600 G2-3200 CCD chip KAF-0402ME KAF-1603ME KAF-3200ME Resolution 768×512 1536×1024 2184×1472 Pixel size 9×9 µm 9×9 µm 6.8×6.8 µm CCD area 6.9×4.6 mm 13.8×9.2 mm 14.9×10.
These cameras are able to acquire color image in single exposure, without the necessity to change color filters. On the other side color mask brings lower sensitivity and limits the capability to perform exposures using narrow-band filters etc. Because each pixel is covered by one of three basic color filters, it is necessary to compute (interpolate) remaining two colors for each pixel, which of course limits resolution of color image.
Illustration 4: Temný proud CCD čipů Kodak používaných v kamerách série G2 Model G2-0402 G2-0402 model uses 0.4 MPx Kodak KAF-0402ME Class 1 or 2 CCD chip. Resolution 768×512 pixels Pixel size 9×9 µm Imaging area 6.9×4.6 mm Full well capacity Approx. 100 000 e- Output node capacity Approx. 220 000 e- Dark current 1 e-/s/pixel at 0°C Dark signal doubling 6.3 °C Model G2-1600 G2-1600 model uses 1.6 MPx Kodak KAF-1603ME Class 1 or 2 CCD chip.
Output node capacity Approx. 220 000 e- Dark current 1 e-/s/pixel at 0°C Dark signal doubling 6.3 °C Model G2-3200 G2-3200 model uses 3.2 MPx Kodak KAF-3200ME Class 1 or 2 CCD chip. Resolution 2184×1472 pixels Pixel size 6.8×6.8 µm Imaging area 14.9×10.0 mm Full well capacity Approx. 55 000 e- Output node capacity Approx. 110 000 e- Dark current 0.8 e-/s/pixel at 0°C Dark signal doubling 6 °C Model G2-2000 G2-2000 uses 2 MPx CCD Kodak KAI-2020.
Full well capacity Approx. 40 000 e- Output node capacity Approx. 100 000 e- Dark current 0.3 e-/s/pixel at 0°C Dark signal doubling 7 °C KAI-4022 CCD detector with color (Bayer) mask can be used in the G2-4000 camera. Camera Electronics 16-bit A/D converter with correlated double sampling ensures high dynamic range and CCD chip-limited readout noise. Fast USB interface ensures image download time within seconds. Maximum length of single USB cable is 5 m.
Model G2-0402 Gain 1.5e-/ADU (1×l binning) 2.3e-/ADU (other binnings) System read noise 12 e- (LN read) 15 e- (Standard read) Full frame download 0.6 s (LN read) 0.5 s (Standard read) Model G2-1600 Gain 1.5e-/ADU (1×l binning) 2.3e-/ADU (other binnings) System read noise 12 e- (LN read) 15 e- (Standard read) Full frame download 2.5 s (LN read) 2.1 s (Standard read) Model G2-3200 Gain 1.0 e-/ADU (1×l binning) 1.
Model G2-4000 Gain 1.0 e-/ADU (all binnings) System read noise 7 e- (LN read) 10 e- (Standard read) Full frame download 6.8 s (LN read) 5.7 s (Standard read) System read noise depends on the particular CCD detector. For instance KAF0402 or KAF-1603 CCDs can be read with 11 11 e- RMS, read noise of the KAF-3200 CCD can be less than 6 e- RMS. Download times are valid for cameras of revision 3 and newer. Download times for cameras of revision 2 was approx.
TEC modules Two stages Maximal ∆T >50 °C below ambient Regulated ∆T 48 °C below ambient (85% cooling) Regulation precision ±0.1 °C Hot side cooling Forced air cooling (fan) Optional heat exchanger for liquid coolant Maximum temperature difference between CCD and ambient air may exceed 50 °C when the cooling runs at 100% power. However, temperature cannot be regulated in such case, camera has no room for lowering the CCD temperature when the ambient temperature rises.
control software. Input voltage is displayed in the Cooling tab of the CCD Camera control tool in the SIMS. This feature is important especially if you power the camera from batteries. Warning: The power connector on the camera head uses center-plus pin. Although all modern power supplies use this configuration, always make sure the polarity is correct if you use own power source. Mechanical Specifications Compact and robust camera head measures only 114×114×74 mm (4.5×4.5×3 inches).
Package Contents G2 CCD cameras are supplied in the foam-filled, hard carrying case containing: ● Camera body with a user-chosen telescope adapter. The standard 2" barrel adapter is included by default. If ordered, the filter wheel is already mounted inside the camera head and filters are threaded into place (if ordered). ● A 100-240 V AC/50-60 Hz input, 12 V DC/5 A output power supply adapter with 1.5 m long output cable. The adapter includes AC cable.
● A CD-ROM with camera drivers, SIMS software package with electronic documentation and PDF version of this manual. ● A printed copy of this manual. Optional components Number of optional parts are available for G2 CCD cameras. These parts can be ordered separately. Refer to our web site for the pricing, please. Filter Wheel for five 1.25 inch threaded filter cells Because the filter wheel is not necessary for some applications (e.g.
Another filter wheel can be also ordered separately. Replacing the whole filter wheel is easier than replacing individual filters. It is possible to thread for instance LRGB filter set into one wheel, BVRI set into second wheel and narrow-band filters (Hα, OIII, ...) into the third one. Filter Wheel for six 1-inch glass-only filters Another option is using of 1-inch, glass-only filters in 6-positions filter wheel. 1-inch filter is big enough to cover all sizes of CCD chips used in G2 CCD cameras.
contains high-pass Red, Green and Blue filters plus Luminance filter covering the combined RGB spectral range, blocking IR and UV portion of spectrum for maximum color accuracy. Clear (C) filter Optional clear filter (optical glass with AR coatings) of the same thickness like RGB filters can be used in addition to (or instead of) Luminance filter to use maximum chip QE for luminance images.
Telescope adapter The camera is supplied with standard 2" barrel adapter by default, but the user can choose any other adapter he/she prefers. Another adapters can be ordered separately. It is possible to choose among various telescope/lens adapters: 22 1.25" barrel adapter Adapter for 1.25" focusers. 2" barrel adapter Adapter for 2" focusers. T-thread short M42×0.75 mm inner thread, 8 mm long. T-thread long M42×0.75 mm inner thread, preserves 55 mm back focal distance as defined by Tamron.
Canon EOS lens adapter Standard Canon bayonet adapter Nikon F lens adapter Standard Nikon F bayonet adapter PSB-1100 adapter Threaded adapter for TeleVue PSB-1100 coma corrector Adapters are attached to the camera body using four M3 (3 mm metric) screws, placed on the corners of 44 mm square. Custom adapters can be made upon request.
Getting Started Although the camera is intended for operation at night (or for very low-light conditions at day), it is always better (and highly recommended) to install software and to make sure everything is working OK during day, before the first night under the stars.
site. Reject this offer (choose “No, not this time”) and click “Next” button. 2. Choose the “Install the software automatically” in the next step. Insert the CD-ROM into the drive and the wizard will continue by the next step. It is not necessary to install files from CD-ROM. It is possible to copy the folder containing driver files e.g. to shared network volume, USB Flash Disk etc. Then it is necessary to choose the “Install from a list or specific location” and to define the path to driver files. 3.
USB port (different USB connector on the PC or through the USB hub), Windows reports “found new hardware” again and asks you to install the software. Repeating the installation again brings no problem, but you can also point Windows to use the same “oemXX.inf” (in the “\windows\inf” folder) and “g2ccd2.sys” (in the “\windows\system32\drivers” folder) files, which are already installed.
g1ccd = g1ccd.dll g2ccd2 = g2ccd2.dll g3ccd = g3ccd.dll [GPS] GarminUSB = gps18.dll NMEA = nmeagps.dll [Telescope] NexStar = nexstar.dll LX200 = lx200.dll Individual sections define which driver would be loaded and asked to enumerate all connected devices of particular type (CCD cameras, GPS receivers, telescope mounts). SIMS package already contains this file containing all included drivers.
to provide information about available filters (if the particular camera has the integrated filter wheel, of course). But the user can order camera with various filters, or he or she can change individual filters or the whole filter wheel etc. There is no way how to determine the actual filters in the filter wheel automatically. This is why the G2 CCD camera driver for SIMS reads the “g2ccd2.ini” or “g3ccd.
Illustration 9: Filters offered by the CCD Camera tool Camera Connection Camera connection is pretty easy. Plug the power supply into the camera and connect the camera to the computer USB port using the supplied USB cable. Note the computer recognizes the camera only if it is also powered. Camera without power act the same way as the unplugged one from the computer point of view.
starts to rotate and the camera control unit searches for the filter wheel home position. This operation takes a few seconds, during which the camera does not respond to computer commands. Camera indicates this state by flashing the orange LED. See the “Camera LED state indicator” chapter for details. The camera is fully powered by the external power supply, it does not use USB cable power lines.
directly to USB ports available on the computer I/O panel or through the USB hub. The operating system assigns unique name to every connected USB device. The name is rather complex string derived from the device driver GUID, USB hub identifiers, USB port number on the particular hub etc. Simply put, these identifiers are intended for distinguishing USB devices within operating system, not to be used by computer users.
Camera Operation Camera operation depends on the software used. Scientific cameras usually cannot be operated independently on the host computer and G2 CCD also needs a host PC (with properly installed software) to work. Camera itself has no displays, buttons or other controls. On the other side, every function can be controlled programmatically, so the camera is suitable for unattended operation in robotic setups. Plug the camera into computer and power supply and run the SIMS program.
Camera and the Telescope The camera needs some optical system to capture real images. It depends on the telescope adapter to which telescopes (or lenses) the camera can be connected. Small 1.25" barrel adapter can be used only on cameras with small CCDs. Standard 2" barrel adapter is recommended if your telescope is equipped with 2" focuser – higher diameter ensures more robust connection.
(SIMS User's Guide explains why cooling is important to reduce thermal noise). If you plug the G2 CCD to power supply, you may notice the fans on the back side of the camera head start operation. These fans take away the heat from the hot side of the Peltier modules, which cool the CCD chip. Fans are running continuously, independently on the Peltier cooler (they are also used to cool down the camera power supplies etc.). Peltier cooler can be controlled from the “Cooling” tab of the SIMS CCD Camera tool.
target temperature is displayed in cyan color on the graph. The current chip temperature is displayed in red. Also notice the blue line, which displays the cooling utilization – it starts to grow from 0% to higher values. Also notice the yellow line in the graph – it displays camera internal temperature. This temperature also somewhat grows as the cooling utilization grows. The hot air from the Peltier hot side warms up the camera interior slightly.
First Images Actual exposure is performed from the “Exposure” tab of the CCD Camera tool. Illustration 15: Exposure tab of the CCD Camera Control tool It is necessary to define few parameters before the first shot. First, it is necessary to define the image type – choose “Light” from “Exposure” combo box. Then choose the exposure time. If you experiment with exposures in the dark room with a camera connected to some f/6 refractor, start with 1 second.
options for every exposure type separately. So it is possible e.g. to define separate folders for dark frames and for flat fields. Always check whether new image processing options are defined properly before you start any exposure. If you choose “Dark” from “Exposure” combo box (remember the image handling options on the right side changes – make sure they are properly defined), image will be captured without opening the shutter.
better with the related horizontal sliders. Observe how the image view is changed when you alter these values. The best positions of Low and High control are as follows: the Low count should be on the count value representing black on the image. Any pixel with value lower than this count will be displayed black. The High count should be on the count value representing white on the image. Any pixel with value higher than this count will be displayed white.
Illustration 17: The raw image downloaded from the camera The Dark frame is taken with the same exposition time at the same CCD chip temperature. Because hot pixels are less stable than normal pixels, it is always better to take more dark frames (at last 5) and to create resulting dark frame as their average or better median.
Illustration 20: Flat field represents the telescope/camera response to uniformly illuminated field Illustration 21: Fully calibrated image with dark frame subtracted and applied flat field CCD image calibration is described in detail in the SIMS User's Guide. Refer to the “Introduction to CCD Imaging” and “Calibrate Tool” chapters for calibration description in theory and in practice. Color Images with monochrome camera and filters Color images are definitely more appealing than black and white ones.
● Color CCD chips have one fixed set of filters without the possibility to exchange them or to completely remove them. Monochrome chip is capable to take images with narrow-band filters like Hα, OIII, etc. ● Color chips have less Quantum Efficiency (QE) then monochrome ones. Limiting QE from around 80% to around 30% by color filters only wastes light in number of applications.
Illustration 22: “(L)RGB Image Add“ tool in SIMS... Illustration 23: ...
If we take images for individual colors and also luminance image, possibly with different binning and exposure times, the calibration starts to be relatively complex. We need dark frame for every exposure time and binning. We need flat field for every filter and binning. We need dark frames for every flat field. This is the price for beautiful images of deep-sky wonders.
There are several algorithms for calculating missing color components of individual pixels – from simply using of color from neighboring pixels (this method provides quite coarse images) to more accurate methods like bilinear or bicubic interpolation. There are even more sophisticated algorithms like pixel grouping etc. No G1 camera performs the Debayer processing itself. The raw image is always passed to the host PC and processed by control software.
the original raw image. Also please note the settings of the “Bayer X odd” and “Bayer Y odd” check boxes must be altered when any geometric transformations are applied to the raw image (e.g. mirroring, rotation, etc.). Some transformations (e.g. soft binning or resampling) cannot be performed on raw image at all. It is always better to Debayer images first and process them later. Also note that stacking of raw color images results in loss of color information.
Illustration 25: Histogram and Stretch tool shows histograms of individual colors 46
Some General Rules for Successful Imaging Advanced CCD cameras caused a revolution in amateur astronomy. Amateurs started to capture images of deep-sky objects similar or surpassing the ones captured on film by multi-meter telescopes on professional observatories. While the CCD technology allows capturing of beautiful images, doing so is definitely not easy and straightforward as it may seems.
● Focus image properly. Almost unnoticeable focuser shift affects star diameter. Focusing, especially on fast telescopes, is critical for sharp images. Electrical focuser is a huge advantage, because it allows focusing without shaking the telescope by hand and with precision surpassing the manual focusing. Keep on mind that the star images are affected not only by focusing, but also by seeing. Star images will be considerably bigger in the night of poor seeing, no matter how carefully you focus.
successful night out. Nights can become cloudy or foggy, the full Moon can shine too much, the seeing can be extremely bad… Number of things can come bad, but the bad luck never lasts forever. Start with bright objects (globular clusters, planetary nebulae) and learn the technique. Then proceed to more difficult dimmer objects.
Camera Maintenance The G2 CCD camera is a precision optical and mechanical instrument, so it should be handled with care. Camera should be protected from moisture and dust. Always cover the telescope adapter when the camera is removed from the telescope or put the whole camera into protective plastic bag. Desiccant exchange The G2 CCD cooling is designed to be resistant to humidity inside the CCD chamber.
amount of water absorbed – it is bright orange when it is dry and turns to transparent without any color hue when it becomes wet. The temperature range for drying of the the used silica-gel is 130 to 160 °C. Silica-gel container construction differs on different G2 camera revisions. Changing the silica-gel in G2 cameras revision 3 G2 cameras revision 3 and higher have the container accessible from the back side of the camera head.
The desiccant chamber used in G2 cameras revision 3 and higher can be filled with a hot silica-gel without a danger of damaging of the container. Changing the silica-gel in G2 cameras revision 1 and 2 G2 cameras revision 1 and 2 have the desiccant container inside the camera head. So it is necessary to open the camera head by unscrewing of the 6 bolts on the back side of the camera head first (opening of the camera head is describe in the chapter about changing of the filters).
Illustration 27: Desiccant chamber inside the G2 CCD head Warning: Do not fill the plastic chamber in the G2 cameras revision 1 and 2 with hot silica gel. Let it cool down first, preferably in some hermetically closed container. It is also possible to put the fresh silica gel bag into the container to dry it first. The silica gel chamber is separated from the CCD chamber itself with a very faint stainless steel grid. It is possible to use silica gel with very small grains.
Camera cannot be opened in such case. Opening the camera head of G2 cameras revision 1 and 2 The blade shutter rotates 180° between individual snapshots, but only the initial position is safe for removing the camera cover in the case of camera revisions 1 and 2, because the shutter can interfere with the filter wheel drive if it remains in the second position and the camera head is opened.
Illustration 28: Filters can be changed after opening the camera case front shell Every filter position in the wheel is defined by the index hole. The hole defining the first position is preceded by another hole. Older versions of G2 cameras (revisions 1 and 2) have a filter wheel of 98 mm diameter, later versions (revisions 2 and 3) use filter wheels of 95.5 mm diameter.
Illustration 29: Filter positions on filter wheels with 5 and 6 positions and 98 mm diameter Illustration 30: Filter positions on filter wheels with 5 and 6 positions and 95.
Changing the Whole Filter Wheel The whole filter wheel can be changed at once. It is necessary to remove the front part of the camera case the same way as in the case of changing filters.The filter wheel can be removed when you unscrew the bolt on the center of the front part of camera case. Take care not to damage the horseshoe-shaped optical bar when replacing the filter wheel. Changing the Telescope Adapter The camera head contains bolt square. The telescope adapter is attached by four bolts.
