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Warnings About COSMIC

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

Stowing the Guider:

It is good practice to stow the guider with the "STOW" button on the GUI at the end of the night, and before any telescope slewing. It is also good practice to click off the frame grabber "enable" button on the Sheperd autoguider display at the end of the night and before slewing the telescope.

The Shutter is SLOW:

The COSMIC shutter is not reliable or repeatable for exposures of less than 2 seconds. When using the focus script it is recommended to expose for at least 5 seconds to eliminate seeing effects.

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 (2 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.

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