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.
Figure 4.8: The Dewar Adjustments 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.