Guider camera requirements
There are a number of constraints from the guider system and from the available CCD detectors that will largely determine the design and properties of the guider camera.

Guider Camera requirements
Parameter
Value
Units
Frame rate (binned)
4
fps
Subraster rate
(50 × 50 pixels)
10
fps
Field of View
2
arcmin2
Resolution
0.2
arcsec/pixel
Sensitivity
80%
peak
Readout Noise (max)
10
e-

The full frame update rate of the guider camera needs to be fast enough not to annoy the observer. The subraster frame rate of the guider camera must be fast enough to track tip--tilt of the atmosphere, telescope shake and dome-induced seeing.

The resolution and field-of-view are set by the size of the detector, and the re-imaging optics in front of the guide camera. The trade-off is that the resolution must be fine enough to provide precise centroids, while the field-of-view (FOV) must be large enough to make it straightforward to acquire suitable guide stars.

Essentially, the requirements dictate the use of a back-illuminated, frame-transfer, low-noise CCD with an image area of 512 × 512 pixels. For a pixel size of 26 µm (or 13 µm binned 2×2), the re-imaged beam would be f/4.


Greg Burley (burley@obs.carnegiescience.edu)
Ian Thompson (ian@obs.carnegiescience.edu)