next up previous
Next: About this document ... Up: User Manual for COSMIC Previous: Direct Imaging with COSMIC

Warnings About COSMIC

The following are items about which all COSMIC observers should be fully aware.

Stowing the Guider:
The guider should be stowed before slewing the telescope, otherwise passing over a bright star could fry the guide camera. Stowing the guider is accomplished in the instrument window by pressing the STOW button. The guider should also be stowed at the end of the night.
Turning Off the Guider:
The guider should be turned off any time there is significant ambient light in the dome. This can only be done from within the prime focus cage. Ask a technician or night assistant how to do this. The guider then needs to be turned on at the beginning of the night.

Turning Off Lamps During Readout:
There is significant light leakage even with the shroud in place, so gradients will occur if lamps are left on during readout. This leakage also makes most twilight flats nearly impossible to obtain.

Restarting COSMIC window:
Quit the current window. Then type ``cosmic'' in any XTERM or CMDTOOL window. The data taken will be written to this directory.

Aborting Exposures:
After aborting an exposure, it is necessary to take a short (1 second) SNAP exposure in order to clean the charge off the array.

Twilight imaging flats:
The light leaks in COSMIC are bad enough that it is impossible to take proper flat-field images of the twilight sky. The problem is that the light leaks in during the long readout, causing the response to vary due to the readout, not the desired illumination pattern.

Snap mode:
After taking an image in SNAP mode ( binning), make sure to reset the binning to to take a normal image.


next up previous
Next: About this document ... Up: User Manual for COSMIC Previous: Direct Imaging with COSMIC
Roy Gal
4/25/1998