Dewar Parameters

This menu provides for several adjustments of the Stepper Motors and GSM. Again, these commands are needed infrequently so they are placed in a special menu.

• Filter and Slit Wheel stepping: These controls allow fine adjustments to the positions of the stepper motors. For example, if the slit image is not perfectly vertical on the array, you will want to move the slit motor a few steps. Likewise, if the filter wheel is not correctly positioned, some vignetting at the edge of the detector may be noticeable. Simply set the desired Step Amplitude (1 unit corresponds to the distance from one filter or slit to the next), and press Step Up or Step Down. Note that ``up'' and ``down'' correspond to the odometer numbers, and that moving ``up'' actually moves the slit image down on the detector.

• GSM Zero Points: Instead of stepping the GSM a few pixels at a time from the GSM menu, the Zero Point values can be entered directly in the text-entry fields in this menu. Note, however, that the GSM is usually very reliable. If large changes to the zero point values are needed, the Pots on the GSM electronics are probably incorrectly adjusted. You cannot simply correct large errors in the pots by resetting the zero points -- the entire GSM calibration will be thrown off.

• GSM Calibration: This allows one to reset the relative calibration between the GSM fine and coarse sensor servo loops. Again, these controls should be used sparingly and only after the Coarse and Fine Voltage Pots on the GSM electronics box have been set correctly.