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G2-2000 and G2-4000 CCD Cameras
 This series of G2 CCD cameras was developed especially with astro-photographers on mind. These cameras utilize sensitive, low noise Kodak KAI Interline-transfer CCD detectors with anti-blooming gates and electronic shutter with short-exposure capability. Updated version of camera electronics with High-speed USB2.0 interface provides fast image download and very low camera read noise. Other camera features are identical to the G2 series cameras based on Full-frame Kodak KAF CCD detectorsvery efficient two-stage Peltier CCD cooling up to 50 degrees Celsius below ambient temperature, simple 12VDC power supply, compact and robust camera head with mechanical shutter and optional 5 or 6-positions filter wheel.

While scientific applications require CCD detectors with maximum quantum efficiency, very low noise, high dynamic range and linear response to light, astro-photographers rather appreciate anti-blooming to be able to acquire wide-field images with bright stars without blooming spikes and electronic shutter for very short exposures of Moon and planets. Some astro-photographers also prefer single-shot-color cameras not to bother with filters and combination of resulting images from individual color images. New CCD cameras G2-2000 and G2-4000 provide all these features.

G2 CCD camera head

G2 CCD camera head

Both camera models, based on Kodak KAI CCDs, share important features with the Kodak KAF CCD based G2-0402, G2-1600 and G2-3200 models intended for scientific applications and narrow-band imaging:

  • Compact camera head, small and lightweight enough to be attached even to small telescopes.

  • Hight-quality, very low-noise electronics for images with maximum S/N and without artificial gradients and other artifacts.

  • Efficient and precisely regulated CCD chip cooling up to 50C below ambient temperature.

  • Integrated all-in-one design with USB and power connectors directly on the camera head.

  • Integrated shutter not to bother with covering the telescope when taking dark frames.

  • Integrated filter wheel for standard filters to take (L)RGB or narrow-band images.

  • Single-voltage power supply enabling operation from 12Vbattery or “brick” adapter.

  • Fast image transfer over High-speed USB connection to the host PC with Plug and Play driver installation.

  • Wide choice of various adapters for all common standards of telescopes, coma-correctors, focal reducers or field flatteners, microscopes, photographic lenses etc.

  • Robust construction to sustain every-day usage.

  • Rich software support.

Other features are especially important for astro-photographes:

  • Strong anti-blooming gates ensure proper images of bright stars in the field of view without blooming spikes.

  • Electronic shuttering allows very short exposures of bright objects like Moon and the planets.

  • Fast windowing allows reading of arbitrary detector sub-frame faster than in the case of KAF CCD detectors.

  • Single-shot color camera variants with advanced multi-pass color (Bayer) pattern demosaicing in software.

G2-4000 CCD camera head

G2 CCD series with Kodak KAI CCDs include four models:

Model CCD Chip Color mask Resolution Pixel size Imaging area Download time
G2-2000 KAI-2020 Monochrome None 1604נ1204 7.4נ7.4μm 11.9נ8.9mm ~ 2.6s
G2-2000C KAI-2020 Color Bayer RGBG 1602נ1202 7.4נ7.4μm 11.9נ8.9mm ~ 2.6s
G2-4000 KAI-4022 Monochrome None 2056נ2062 7.4נ7.4μm 15.2נ15.3mm ~ 5.7s
G2-4000C KAI-4022 Color Bayer RGBG 2054נ2060 7.4נ7.4μm 15.2נ15.3mm ~ 5.7s

Remark:

G2-2000C and G2-4000C use CCD detector with color mask applied to individual pixels, so they are capable to take color image in single exposure, but at the price of lower sensitivity. These cameras are not equipped with filter wheel for color filters. While it is possible to use filter wheel also in these camera models e.g. for narrow-band imaging, using of monochrome detectors brings much better results in these cases.

Lower resolution of color camera models are caused by the necessity to interpolate colors of each pixel from surrounding pixels. Monochrome raw image taken by color cameras are of the same resolution like in the case of monochrome cameras.

G2CCD cameras are designed to work in cooperation with a host Personal Computer (PC). As opposite to digital still cameras, which are operated independently on the computer, the astronomical slow-scan, cooled cameras usually require computer for operation control, image download, processing and storage etc. To operate G2 CCD camera, you need a computer which:

  1. Is compatible with a PC standard.

  2. Runs a modern 32-bit Windows operating system.

    Remark:

    G2 camera USB driver is designed for Windows2000 and better operating systems (e.g. WindowsXP). Older 16/32-bit systems, like Windows 95/98 and Windows Me, are not supported. G2 CCD cameras cannot properly operate with such operating systems.

  3. Provides at last one free USB port.

    Remark:

    The current series of G2CCD cameras are designed to operate with USB2.0 high-speed (480Mbps) hosts. Although they are fully backward compatible with USB1.1 full-speed (12Mbps) hosts, image download time can be somewhat longer if USB1.1 connection is used.

G2 CCD Cameras Technical Specifications

CCD Chip

G2-2000 and G2-4000 cameras use low noise Kodak KAI Interline Transfer CCD detectors. Advanced manufacturing techniques like transparent electrodes and microlensing ensure maximum quantum efficiency of monochrome models 55%. The inherent dark current as well as read noise is very low, so the resulting image S/N ratio is very good.

Kodak KAI-2020 inside the G2-2000 CCD camera

Kodak KAI-2020 inside the G2-2000 CCD camera

Model G2-2000 and G2-2000C

G2-2000 model uses 2MPx Kodak KAI-2020 CCD chip.

Resolution 1604 (H)נ1204 (V) pixels
Pixel size 7.4μm (H)נ7.4μm (V)
Imaging area 11.9mm (H)נ8.9mm (V)
Full well capacity ~40,000 e-
Dark current 40 e-/s/pixel at 40C

KAI-2020 CCD chip specifications

KAI-2020 CCD chip and its Quantum Efficiency

Model G2-4000 and G2-4000C

G2-4000 model uses 4MPx Kodak KAI-4022 CCD chip.

Resolution 2056 (H)נ2062 (V) pixels
Pixel size 7.4μm (H)נ7.4μm (V)
Imaging area 15.2נ15.3mm
Full well capacity ~40,000 e-
Dark current 40 e-/s/pixel at 40C

KAI-4022 CCD chip specifications

KAI-4022 CCD chip and its Quantum Efficiency

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 5m. This length can be extended for instance to 10m by using single USB hub or USB active extender cable. Up to 100m extension can be achieved with third-party extender.

ADC resolution 16 bits
Sampling method Correlated double sampling
Read modes Standard
Low-noise
Horizontal binning 1 to 4 pixels
Vertical binning 1 to 4 pixels
Sub-frame readout Arbitrary sub-frame
Computer interface USB 2.0 High Speed
USB 1.1 Full Speed compatible

Camera electronics specifications

Image download time depends on the CCD chip used in particular camera model. Also the read noise depends on the chip as well as on the read mode.

  • Standard read mode provides system read noise approx. 1e- above CCD chip read noise.

  • ULN (ultra low-noise) read mode is somewhat slower (approx. 1.2), but ensures system read noise equal or smaller than the manufacturer-specified chip read noise.

Model G2-2000

Gain 0.4 e-/ADU (1נ1 binning)
0.8 e-/ADU (other binnings)
System read noise 7 e- RMS (LN read)
9 e- RMS (standard read)
Full frame download 3.1 s(LN read)
2.6 s(standard read)

G2-2000 electronics specifications

Model G2-4000

Gain 0.4 e-/ADU (1נ1 binning)
0.8 e-/ADU (other binnings)
System read noise 7 e- RMS (LN read)
9 e- RMS (standard read)
Full frame download 6.8 s(LN read)
5.7 s(standard read)

G2-4000 electronics specifications

Notes:

  1. Binning can be combined independently on both axes

  2. Download times are valid for USB2.0 host and may vary depending on host PC. Times stated here were measured on 1.5GHz PentiumM based laptop computer.

    Download times can be somewhat longer when connected to USB1.1 host.

Power and USB connectors on the bottom of the camera head

Power and USB connectors on the bottom of the camera head

Chip Cooling

Regulated two-stage thermo-electric chip cooling up to 50C below ambient temperature with forced air cooling and 0.1C temperature precision ensure very low dark current for long exposures.

CCD chip cooling Thermoelectric (Peltier modules)
TEC modules Two stages
Max. delta T 50C below ambient maximum
45C below ambient typical
Regulation precision 0.1C
Hot side cooling Air cooling (50mm fan)

Chip cooling specifications

Fan and air output vents on the back side of the camera

Fan and air output vents on the back side of the camera

Notes:

  1. It is not recommended to cool the chip to the maximum temperature difference, else the camera cannot guarantee temperature stability when the ambient air temperature rises. It is usually practical to set the temperature so the cooling utilization varies around 90%. This provides enough reserve in cooling power to keep the CCD temperature even if the ambient temperature rises several degrees Celsius.

  2. Water-assisted cooling is available for all G2CCD cameras. Contact the manufacturer for details.

  3. The cooling performance depends on the environmental conditions and also on the power supply. If the power supply voltage drops below 12V, the maximum temperature difference is lower.

  4. One 50mm fan is used in G2 cameras revision 3 and higher. Older revisions used two 40mm fans.

Temperature in the CCD chamber can drop up to -50C

Temperature in the CCD chamber can drop up to -50C

Power supply

The 12VDC power supply adapter enables camera operation from arbitrary power source including batteries, wall adapters etc. Universal 100240VAC/5060Hz, 60W “brick” adapter is supplied with the camera. Although the camera power consumption does not exceed 30W, the 60W power supply ensures noise-free operation.

Camera head supply 12VDC
Camera power consumption 15W without cooling
40W with 100% cooling
Adapter input voltage 100-240VAC/50-60Hz
Adapter output voltage 12VDC/5A
Adapter maximum power 60W

Power supply specifications

Notes:

  1. Camera power consumption is measured on the AC outlet of the 12Vpower supply.

  2. The camera contains its own power supplies inside, so it can be powered by unregulated 12VDC power sourcethe input voltage can be anywhere between 10 and 14V. However, some parameters (like cooling efficiency) can degrade if the supply drops below 11V.

  3. G2 CCD camera measures its input voltage and provides it to the control software. Input voltage is displayed in the Cooling tab of the CCD Camera control tool in the SIPS. This feature is important especially if you power the camera from batteries.

12VDC/5A power supply adapter for G2CCD Camera

12VDC/5A power supply adapter for G2CCD Camera

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 114נ114נ77mm (approx. 4.5נ4.5נ3inches). The head is CNC-machined from high-quality aluminum and black anodized. The head itself contains USB-B (device) connector and 12VDC power plug, no other parts (CPU box, USB interface, etc.), except a “brick” power supply, are necessary. Integrated mechanical shutter allows streak-free image readout, as well as automatic dark frame exposures, which are necessary for unattended, robotic setups. Integrated filter wheel contains 5 positions for standard 1.25" threaded filter cells. Avariant of filter wheel with 6positions for 1" “glass-only” filters is also available.

5-positions filter wheel and blade shutter inside the G2 camera head

5-positions filter wheel and blade shutter inside the G2 camera head

Internal mechanical shutter Yes, blade shutter
Shortest exposure time 100 ms
Longest exposure time Limited by chip saturation only
Internal filter wheel 5 positions for 1.25" threaded filter cells
6 positions for 1" bolt-secured filters
Head dimensions 114mmנ114mmנ77mm
Back focal distance 29mm
Camera head weight 1.1kg

Mechanical specifications

Slightly slimmer variant of the camera head without internal filter wheel is available. The head dimensions are 114נ114נ65mm (approx. 4.5נ4.5נ2.5inches). This variant allows attaching of external filter wheel with 10 or 12 positions for D36mm or D31mm filters.

G2 CCD camera with external filter wheel attached

External filter wheels for 10 filters D36mm (left) and for 12 filters D31mm or with M28.5נ0.6 threaded cells (right)

Head dimensions 114mmנ114mmנ65mm
Back focal distance 29mm
Back focal distance 16.5mm
Back focal distance from external filter wheel 33.5mm
Weight of camera head 0.9kg
Weight of camera head + external filter wheel 1.7kg

Mechanical specifications

Notes:

  1. Shortest exposure time 100ms is available on G2 cameras revision 3 and higher. Shortest exposure time of older revisions was 175ms.

Software Support

Powerful SIPS (Scientific Image Processing System) software supplied with the camera allows complete camera control (exposures, cooling, filters) with automatic sequences and complete image calibration. SIPS also supports advanced tools like Image Add tool with automatic sub-pixel image alignment, (L)RGB Add tool, Image Blink tool, image filters and many more functions.

Simple Image Manipulation System

Drivers for third-party software are also available (e.g. MaxIm DL, AstroArt, etc.). Visit the “download” portion of the manufacturer web site for current list of available drivers, please.

Automatic guiding

SIPS software package allows automatic guiding of the astronomical telescope mounts using separate guiding camera. Proper and reliable automatic guiding utilizing the computational power of Personal Computer (e.g. calculation of star centroid allows guiding with sub-pixel precision) is not simple task. Guiding complexity corresponds to number of parameters, which must be entered (or automatically measured). And the number of necessary parameters lead to splitting of the “Guiding” tab in the SIPS into two separate tabs. The first one is called “Guiding setup” and it summarizes all parameters necessary for proper autoguiding setup.

Guider setup tab of the SIPS CCD Camera control tool

Guider setup tab of the SIPS CCD Camera control tool

The second tab called “Guiding” thereafter allows switching of autoguiding on and off, starting of the automatic calibration procedure and recalculation of autoguiding parameters when the telescope changes declination without the necessity of new calibration. Also swapping of the German Equatorial mount no longer requires new autoguider calibration.

This tab also graphically displays time history of guide star offsets from reference position in both axes. The length of graph history as well as the graph range can be freely defined, so the graph can be adjusted according to particular mount errors and periodic error period length.

SIPS automatic guiding

SIPS automatic guiding

Complete log of calibration procedure, detected offsets, correction pulses etc. is also shown in this tab. The log can by anytime saved to log file.

G2 cooled imaging camera with G0 high-performance guider

Advanced reconstruction of color information of single-shot-color cameras

Color CCD detectors have red, green and blue filters applied directly on individual pixels (so-called Bayer mask).

Schematic diagram of color CCD detector with Bayer mask

Schematic diagram of color CCD detector with Bayer mask

Every pixel registers light of particular color only (red, green or blue). But color image should contain all three colors for every pixel. So it is necessary to calculate missing information from values of neighboring pixels.

Magnified crop of raw image captured by color camera

Magnified crop of raw image captured by color camera

There are many ways how to calculate missing color valuesfrom simple extending of colors to neighboring pixels (this method leads to coarse images with visible color errors) to methods based on bi-linear or bi-cubic interpolation to even more advanced multi-pass methods etc.

Previous image with colors calculated using bi-linear interpolation

Previous image with colors calculated using bi-linear interpolation

Bi-linear interpolation provides significantly better results than simple extending of color information to neighboring pixels and still it is fast enough. But if the telescope/lens resolution is close to the size of individual pixels, color artifacts appear close to fine details, as demonstrated by the image above.

The same raw image, but now processed by the multi-pass de-mosaic algorithm

The same raw image, but now processed by the multi-pass de-mosaic algorithm

Multi-pass algorithm is significantly slower compared to single-pass bi-linear interpolation, but the resulting image is much better, especially in fine details. This method allows using of color camera resolution to its limits.

SIPS offers choosing of color image interpolation method in both “Image Transform” and “New Image Transform” tools. For fast image previews or if the smallest details are significantly bigger than is the pixel size (be it due to seeing or resolution of the used telescope/lens) the fast bi-linear interpolation is good enough. But the best results can be achieved using multi-pass method.

Shipping and Packaging

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).

  • A100-240VAC input, 12VDC output “brick” adapter with 1.8m long power cable.

  • 5m long USB A-B cable for connecting camera to host PC.

  • ACD-ROM or USB Flash Drive with camera drivers, SIPS software package with electronic documentation and PDF version of User'sManual.

  • Aprinted copy of User'sManual.

G2 CCD cameras are shipped in the foam-filled carrying case (left), larger case is used if camera is ordered with external filter wheel (right)

Image Gallery

Example images captured with G2 KAI cameras.

Object M42 Orion Nebula
Author Samuele Gasparini
Camera G2-4000
Telescope SkyWatcher 80ED + 0.85 flattener

Object SH2 155
Author Marco Burali
Camera G2-4000 (H-alpha + OIII + RGB)
Telescope BRC 250 F5

Object NGC2903
Author Marco Burali
Camera G2-4000
Telescope Takahashi TOA 150 F7

Object Virgo Galaxy Cluster
Author Marco Burali
Camera G2-4000
Telescope Takahashi TOA 150 F7

Object NGC7380
Author Marco Burali
Camera G2-4000
Telescope Takahashi TOA 150 F7

Object IC1805
Author Marco Burali
Camera G2-4000
Telescope Takahashi TOA 150 F7

Object NGC884 a NGC869
Author Marco Burali
Camera G2-4000
Telescope Takahashi TOA 150 F7

Object Gama Cygni
Author Marco Burali
Camera G2-4000
Telescope Takahashi TOA 150 F7

All images published with permission of their respective authors.

 
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