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This is an old revision of the document!
At stow:
Slewing to star:
Implemented January-July 2023
At stow:
Slewing to Star:
There is some controversy on whether moving the TelWFS boxes corrupts the reconstructor. During engineering time we should try keeping the boxes fixed at their reference positions when the last reconstructor was made using the CalSource. For these tests, do not move the boxes to center on the red beacon at stow, also do not use Zero Centroids to change the relative positions of the boxes. This might mean that beacon/star will be offset in the ACQ hole. It might be better to use the boxes as the absolute reference rather than the Acq hole.
In February, Norm found that some telescopes performed OK with not moving the boxes and other telescopes could not lock stars without adjusting the boxes. If the WFS boxes need to be moved, then it would be a good idea to create a new on-sky reconstructor and flat using a bright star. The gain should be high enough to give good SNR (without saturating) on the TelWFS when recording on-sky reconstructors.
Action Item: Determine best gain settings for creating on sky reconstructors. Give guidance so operators can determine whether WFS counts are approaching saturation.
Proposed Changes to the Alignment Sequence - rough ideas - comment in different color to provide feedback or propose different steps.
The coordinated Beacon/M7 movements (using STST button on obsgtk) will speed up compensating for big shifts after sending M7 to default.
Please do not experiment with the alignment sequence during science programs, unless the PI requests for the operator to try a new/different approach (that can be done safely) to improve performance.
Notes from Discussion between Julien and Theo:
A shift moves the star into the hole and the detector, while a tilt with star still centered in hole will dim the stars in some external boxes and make stars appear outside of the boxes used, on the opposite side.
About star going out from Acq hole:
1-After alignment, the center of the Acq Hole matches the center of the boxes.
2-Acq Hole plane and detector plane are optically conjugated, means that what happens in Acq Hole is imaged on detector.
3-We have 3 blocks: Acq Hole + Acq camera, Collimator, and WFS (Lenslet + detector).
4-If Acq Hole translates, condition 1 is lost. If it tilts we don't care.
5-If Collimator translates, condition 1 is lost, and illumination of the sub-pupils will change. If it tilts we don't care.
6-If WFS translates, condition 1 is kept, and illumination of the sub-pupils will change. If it tilts condition 1 is lost.
Julien sees no way to explain that star goes away from Acq Hole center while staying at boxes centers and not involving one of those 3 blocks. Whatever happens before Acq Hole in terms of tilt or shear, if the star is centered in boxes and not in Acq (or the opposite) means the initial matching between Acq Hole and Boxes is lost.