Mirror retrieval

Sometimes during the night or when we first start to stack we notice a protrusion in an image or missing mirrors which indicates some mirrors may have drifted out of the stack. Move dome and structure to CCAS and right the tracker when this happens. Also, don’t forget to open the CCAS tower. Do the following.

a) View Hefi Cam 6

b) On HEFI gui put mirror in and light source to high.

c) There should be the array in sight. See if you can see outlying mirrors to confirm.

d) If you do see mirrors out of the main array switch views to AOA (cam 2) and remove HEFI mirror and light source on HEFI gui. If you are at the right focus and GRoC you should be able to see each individual mirror in the array. You might have to left the tracker to identify the missing mirror.

e) Right down any missing mirrors seen in AOA.

f) In AOA wavescope window (KVM 2) we’re going to have to command individual mirror moves by using the command segttp. We can move each mirror in one of three ways: Tip, Tilt, Piston. Refer to Figure 6 above.

g) Switch back to Hefi view (cam 6) and insert mirror and light.

h) Try one of the mirrors you wrote down and make a large move so you can identify the that same mirror in HEFI view. When you are ready to enter the command in AOA the syntax is as follows: < segttp 87 5 0 0 > This command will move mirror 87 a tip of 5, a tilt of 0, and a piston of 0. We rarely need to piston.

i) Once you’ve identified your mirror adjust moves to get it back to the main array in HEFI. It may be useful to switch back and forth between AOA and Hefi to ensure the mirrors are back in place. It also may be useful to do a few stacking iterations after mirror retrieval to tighten the stack up.

j) Once all the mirrors are back, DON’T FORGET to remove Hefi mirror and light source, and close the CCAS tower.