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G1-1200 autoguider and planetary camera—high sensitivity meets low cost
 The G1 series of CCD cameras was extended with a new model G1-1200. The Sony ICX445 CCD detector, used in this camera, is produced using EXview HAD technology and offers high quantum efficiency, comparable to cameras employing much more expensive ICX285 CCD. The 1/3" detector format (4.9 × 3.6 mm) as well as small pixels (3.75 × 3.75 μm) suit to short focal length guiding telescopes. G1-1200 is also good for capturing Moon and planets.

Physical dimensions of the Sony ICX445 CCD detector, used in G1-1200 cameras, correspond to G1-0300 or G1-0800 cameras. But G1-1200 has 1.2 millions pixels measuring only 3.75 × 3.75 μm. The EXview HAD CCD production technology, ensuring high quantum efficiency especially in near infra-red portion of the spectrum, is particularly important for usage in astronomy when capturing dim stars or other objects.

Despite relatively small physical dimension of the CCD chip itself, the package is too large to be used in the round head of G0 cameras. So the 1200 model is available only in somewhat larger head of G1 cameras (similarly to G1-1400 model).

G1-1200 (as well as all new G1 cameras) is equipped with “tripod” thread (left) and contains full-size robust USB connector and standard “autoguider” port (right).

G1-1200 cameras are offered in monochrome as well as color variants:

Model CCD detector Chip architecture Color filters Resolution Pixel size Image area Download time
G1-1200 ICX445ALA progressive none 1296 × 966 3.75 × 3.75 μm 4.9 × 3.6 mm ~ 0.15 s
G1-1200C ICX445AQA progressive RGBG (Bayer) 1296 × 966 3.75 × 3.75 μm 4.9 × 3.6 mm ~ 0.15 s

Image digitization speed can be chosen between 2.5 MPx/s and 8 MPx/s. The whole image can be downloaded in a fraction of second, which is particularly important for automatic guider. Analog/Digital converter resolution is 16 bits (65,536 levels), which is even more than the dynamic range of the used CCD detector.

Remark:

Slower readout can be beneficial e.g. when the G1-1200 camera is connected through USB hub together with another USB device and not enough bandwidth is available. Slower read then leads to uniform image fields without artifacts caused by interrupted transfers.

The CCD detector is equipped with electronic shutter, which allows capturing of very short exposures (shortest exposure is 125 μs). Longest exposure is on the other side limited only by the detector saturation, which allows automatic guiding using much dimmer stars compared to the best web or TV cameras. When coupled with a guiding telescope with focal length around 30 cm and diameter around 8 cm, G1-1200 can detect guiding star after several seconds of exposure time almost anywhere on the night sky.

As well as other G0/G1 cameras also the G1-1200 is equipped with standard “autoguider” port. This port allows direct connection of camera and telescope mount compatible with this standard, introduced by SBIG. The G1-1200 camera has mount switching circuits isolated from the rest of the system (camera itself, USB and host computer), which enhances reliability and noise resistance. Maximum switching current is 150 mA and on state resistance around 10 Ω.

1 R.A. + (Right)
2 Dec + (Up)
3 Dec – (Down)
4 R.A. – (Left)
5 Common (Ground)
6 Not connected

G0/G1 camera autoguider port pins

The guiding itself is performed by the SIPS (Scientific Image Processing System) software or by other camera control software, for which G0/G1 camera driver exists (e.g. MaxIm DL or AstroArt) or which is capable to use general ASCOM camera drivers. Automatic guiding running in SIPS utilizes the computational power of modern PCs to achieve sub-pixel precision of star position, so it can guide very precisely even if a guiding telescope with short focal length is used.

Guiding setup tab in the CCD Camera tool of SIPS software

Guiding setup tab in the CCD Camera tool of SIPS software

SIPS software performs not only guiding, but also allows automatic calibration independently on camera orientation, recalculates calibration parameters when the telescope is moved to different declination so no calibration is needed. The guide star can be kept on defined pixel coordinates, which allows placing of the guide star on the same position during subsequent observations etc. Differences from reference positions are displayed graphically and all guiding actions including measured differences and performed corrections are logged into text window and can be saved into text file.

Guiding tab in the CCD Camera tool of SIPS software

Guiding tab in the CCD Camera tool of SIPS software

Remark:

The G1-1200 camera is supported by the driver distributed with SIPS version 2.2 and later.

If the drivers for third party software packages are used (ASCOM, MaxIm DL, AstroArt), it is necessary to use versions which already contain support for particular camera model. Consult documentation supplied with each driver for a list of supported cameras.

 
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