Dmishiftgroc

—Use this especially when there is a drastic change in temperature.from one night to the next. This command raises and lowers the CCAS DMI to make up for the expansion and contraction of the CCAS tower. It is calculated that one degree C needs about 200 units of dmishiftgroc.

1) On the HEFI GUI, in the center section titled Hefi Operations, move the Mirror In. On the Tracker Panel, select video display 6.

2) Move the HEFI Offset in and out buttons until the stack is roughly in focus to the eye.

3) Click the IOF button and then the OOF button to see first the inside of focus image and then the outside of focus image.

4) If the inside of focus gaps are smaller than the outside of focus gaps, the GRoC is too short so make a negative dmishiftgroc # in the AOA console. Make a correspondingly but positive focus movement in MARS.

5) Conversely, if the outside of focus gaps are smaller, make a positive dmishiftgroc # and a negative MARS focus change.

6) Once you have settled on a dmishiftgroc value, THEN take a CCAS DMI reading. It will change as you change dmishiftgroc values.

7) Once you have run an iteration or two, double-check your dmishiftgroc guess by switching to HEFI view and go inside and outside of best focus value by +/- 1500 HEFI units and seeing that the gaps on either side are the same size.

Look here for closing the focus loop: Closing Focus Loop