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chara:discussion_of_alignment_procedures [2024/03/20 21:44] gail_stargazer |
chara:discussion_of_alignment_procedures [2024/04/23 08:20] (current) denis [Current Alignment Sequence] |
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* When slewing to next star, send M7 to default position and repeat. | * When slewing to next star, send M7 to default position and repeat. | ||
- | ==== New Alignment Sequence ==== | + | ==== Current |
Implemented January-July 2023 | Implemented January-July 2023 | ||
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* Align TelWFS boxes to center on the red beacon. | * Align TelWFS boxes to center on the red beacon. | ||
* Align blue beacon to labAO using dichroic. | * Align blue beacon to labAO using dichroic. | ||
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* If aberration terms are high, ZERO CENTROIDS to adjust relative positions of the boxes. | * If aberration terms are high, ZERO CENTROIDS to adjust relative positions of the boxes. | ||
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* If coma and astigmatism high, create sky flat on bright star - Turn off **[DM]**, **[SV FLT]**, **[FLATEN]**, | * If coma and astigmatism high, create sky flat on bright star - Turn off **[DM]**, **[SV FLT]**, **[FLATEN]**, | ||
* For IR combiners, move beacon flat to align star to STST. | * For IR combiners, move beacon flat to align star to STST. | ||
- | * For SPICA, move beacon flat to align star on SPICA FTT. | + | * For SPICA, move beacon flat to align star on SPICA FTT. <font inherit/ |
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- | * When slewing to the next star, DO NOT send M7 to default. If next star is bright, then align beacon flat to center star on STST/SPICA FTT. If star is faint, keep beacon flat fixed or align beacon flat to center red beacon in offset beacon boxes on TelWFS. | + | |
==== Proposed Revisions to Current Alignment Sequence ==== | ==== Proposed Revisions to Current Alignment Sequence ==== | ||
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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. <font 11pt/ | 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. <font 11pt/ | ||
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**Action Item: | **Action Item: | ||
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+ | Any optic moved behind the acq fold is just trying to compensate for something wrong before the fold which is not the best correction.</ | ||
**Proposed Changes to the Alignment Sequence** | **Proposed Changes to the Alignment Sequence** | ||
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* Send M7 to default. | * Send M7 to default. | ||
* Align red beacon to the reference TelWFS boxes (NOT the offset boxes) using beacon flat. | * Align red beacon to the reference TelWFS boxes (NOT the offset boxes) using beacon flat. | ||
- | * Align blue beacon to lab WFS using DICHROIC. | + | * Align blue beacon to lab WFS using DICHROIC. |
* Lock star on TT and TelAO DM. | * Lock star on TT and TelAO DM. | ||
* Move beacon flat to center star on STST or SPICA FTT. | * Move beacon flat to center star on STST or SPICA FTT. | ||
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* If the next star is bright enough for STST alignment, then send M7 to default and repeat sequence above. [Maybe we only have to do this if next star is far away on sky - new pops, new calibration sequence.] | * If the next star is bright enough for STST alignment, then send M7 to default and repeat sequence above. [Maybe we only have to do this if next star is far away on sky - new pops, new calibration sequence.] | ||
* If the next star is too faint for STST [or close on sky?], then keep M7 fixed at current position and use current method of aligning blue beacon by moving M7 (instead of dichroic). | * If the next star is too faint for STST [or close on sky?], then keep M7 fixed at current position and use current method of aligning blue beacon by moving M7 (instead of dichroic). | ||
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The coordinated Beacon/M7 movements (using STST button on obsgtk) will speed up compensating for big shifts after sending M7 to default. | The coordinated Beacon/M7 movements (using STST button on obsgtk) will speed up compensating for big shifts after sending M7 to default. | ||
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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. | 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. | ||
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+ | __**Engineering Update - UT 2024Apr03**__ | ||
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+ | We experimented a bit with the AO alignment sequence. Specifically, | ||
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+ | * Send M7 to default. | ||
+ | * Align the red beacon to telWFS using the beacon flat. | ||
+ | * Align the blue beacon to labWFS using the dichroic. | ||
+ | * Use STST button to center star on STST (coordinated beacon flat/M7 movements). | ||
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+ | The biggest issue (and the reason why we replaced the third step above with moving M7 instead) is that on large slews (> 90 deg), the blue beacon moves off labAO. To recover, we needed to turn on the laser and move the dichroic to center the laser in the ACQ hole. After the course adjustment, we could then see the blue beacon on labAO again. If we end up using this sequence on sky, perhaps we can calculate the expected motion of the dichroic and move it automatically during the slew. The main motivation for the change is that since the dichroic is causing the misalignment to the lab, it is probably the more correct optic to move vs. M7. | ||
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+ | We tested this with E1, and we were able to keep telAO locked without needing to move the WFS boxes (the star was maybe just slightly on the edge of the ACQ hole when locking the AO loops). DM current was ~ 0.8 A. However, E1 might be one of the scopes where the operators don't ordinarily have to move the WFS boxes much. We can try with additional scopes on future engineering nights and with more diagnostic tools to gauge AO performace (by eye, the star looked good on STST with a bright circular core). | ||