Lick Adaptive Optics
Alignment and Calibration


Conventions
Initial Startup
Basic Alignment
WFS Alignment
IRCAL Initial Alignment
Set Point Source Position
Collimate Parabolas
IRCAL Pupil Alignment
WFS Pointing and Centering
IRCAL Focus
Image Sharpening
Daily NGS Afternoon Alignment


Conventions

The conventions in terminology listed below will make understanding the rest of this document easier. The reader is also assumed to have at least a passing familiarity of the layout of the AO optical bench. Note: Items in brown font refer to instructions using the old system (lgs3, lgs4, lgs6, and lgs10) before the current upgrades. If the new system (lgs7 and lgs14) has a catastrophic failure, we can always go back to the old.

Initial Startup

This assumes that everything has been cabled up properly and plugged in, either in the lab or on the telescope.
  1. Turn on all the pulizzis. These should power on certain items for NGS mode by default.
  2. Turn on power strips in the two black electronics racks that are not connected to the pulizzis. These should power on lgs3, lgs4, lgs6, lgs7, lgs10, lgs11, lgs14, and the ethernet hubs.
  3. Ping the various computers to make sure they are up an running: If you get no reponse, first check to make sure that the power is on and the ethernet cable is connected.
    • lgs8 - Lantronix on the back of the grey rack, communicates with the pulizzi power controllers in the grey rack.
    • lgs10 - No longer used. Single port Lantronix in the motor controller electronics rack, communicates with the galil motor controllers.
    • lgs14 - 8 port Lantronix (that replaces lgs10) in the motor controller electronics rack, communicates with the galil motor controllers.
    • lgs11 - Lantronix in the computer electronics rack, communicates with pulizzis, lgs6, and lgs3.
    • lgs6 - SunOS computer that runs real-time AO code. This is only used if lgs7, the new real-time controller, fails. It will soon be retired when spares are available for all lgs7 components.
    • lgs3 - Computer that runs real-time TT code. This computer needs lgs6 up and running to boot and often does not boot properly when first turned on. After lgs6 is up and running, push the Reset button on lgs3. This may take a couple of tries before properly booting. This computer has been replaced by lgs7 and will only be used if lgs7 fails and can't be replaced.
    • lgs4 - Computer that runs the APD TT system.
    • lgs7 - New real-time control computer. This computer has an odd quirk that it requires a 4 minute warmup once it is powered on. After 4 minutes you can cycle power and it will properly boot.
  4. Start LickAO software.
    1. Log into cairo.ucolick.org as lgs.
    2. Type LickAO new & at the prompt ( if you are using the old lgs6 and lgs3 system, type LickAO lgs6 & ).
    3. Click on Power Up - Power Control and start the power deamon if it isn't running.
  5. Turn on the following through the pulizzis (if not already on):
    1. Servo Motor Controllers (all 3 are Galil controllers)
    2. Red Light Source (RLS)
    3. WFS Camera & Fan
    4. Left Monitor
    5. TT 100V power supply
  6. Start real-time software.
    For lgs6 & lgs3 system:
    1. From LickAO software click on Power Up - PowerUp Checklist.
    2. Go down the list to start each piece of software. More detailed directions are in the LickAO software manual.

    For lgs7 system:
    1. From LickAO software click on Power Up - CentDiag
  7. Start Motor Control software.
    1. From LickAO software click on the Motor Status button.
    2. Start the motor daemon if there isn't one already running.
    3. From the All Motors' Status window, click on All Motors Off button.
    4. Turn on all Filter Wheel power from Power Control window.
    5. Turn on all Stepper Motor Controllers from Power Control window.
    6. Turn on 24V power supply from Power Control window.

Basic Alignment

If all is running ok, the basic alignment outlined below should only take a few minutes to an hour to do. The only way for things to get seriously out of alignment is for the bench to be handled roughly enough to dislodge, bump, or break a piece of equipment. The Lick staff are careful and such misalignment or catastrophic damage is unlikely.
  1. Install alignment pinholes. There are 5 alignment pinholes 3 of which need to be installed: in front of the first parabola, deformable mirror (DM), and the second parabola. Make sure to mount the pinholes such that the number label on the pinhole matches the number label on the post holder and that the scribe marks on the pinhole mounts and postholders are aligned. 2 alignment pinholes are permanently mounted: behind the first mirror after cassagrain focus and before the TT Cube.
  2. Connect battery powered red laser to alignment fiber (or you can connect the HeNe fiber to the alignment laser).
  3. Adjust RLS brightness to maximum if using the HeNe laser. If there is little light coming out of the alignment laser check the following:
    • Fibers are well coupled at the FC connector.
    • Fibers may need to be cleaned.
    • RLS (HeNe) alignment may need adjusting. (Detailed directions to come...)
  4. Move fiber stage out of way. This can be done via software or manually by pushing the stage out of the way and holding it there by inserting a block in the mount to keep it in the out of the way position.
  5. Remove 1st Turning Mirror. This is the mirror just before the cassegrain focus. Unscrew the 3 clamps, on back of mount, holding the mirror in the mount. Make sure that each clamp is put back into the same position as when the mirror was in the mount. The 3 clamps are not identical and not interchangable. If they are swapped the mirror will be in a significantly different position and alignment on the sky will be difficult (sky alignment directions to come later....)
  6. Remove 1st mirror after Cassegrain focus. Remove the 3 spring loaded screws from the front of the mirror mount and carefully remove the mirror.
  7. Align through first pinhole (which is located behind the 1st mirror after cassegrain focus).
    1. Center alignment laser on pinhole by moving the motors on the alignment laser mount. The most sensitive way to do this (for any pinhole alignment) is to make the iris slightly smaller than the laser spot and adjust until there is an even halo of light around the hole.
    2. Reinstall 1st mirror after cassegrain focus.
  8. Align through pinhole #1.
    1. Boot lgs4: turn on from pulizzi and ping to make sure it is up.
    2. From LickAO software, start APD TT controller by clicking on AO Control - LGS APD TT button.
    3. Turn off TT relay (T/T Drive)from pulizzi.
    4. Make sure APD TT set to E-Null (this puts TT mirror at its electrical neutral 0V position)
    5. Turn on TT 100V supply (make sure it is supplying 100V and not in standby mode). The supply may need programming if it has just been turned on. Make sure it is in standby mode, type 100 on the keypad and press enter. Then take it out of standby mode to supply 100V to the mirror.
    6. Move 1st mirror after cassegrain focus to center alignment laser on pinhole #1.
    7. Make sure that alignment laser is roughly centered on the TT mirror. The penalty for being off center is a somewhat reduced field-of-view, approximately 4 arcsec/mm. If it is not something is seriously awry: either the position of the permanently mounted first pinhole has been changed or the position of pinhole #1 has been changed. Easiest to check is beam height. Beam height should be 7.5 inches above the table.
  9. Align through pinhole #2.
    1. Open pinhole #1.
    2. Move 1st mirror after cassegrain focus to center alignment laser on pinhole #2. This should be a small movement.
    3. Close pinhole #1 to see how far off center the spot is. If off center by less than 1mm, proceed to next step.
      NOTE: It is typical that when perfectly aligned through pinhole #2, that the spot will be low (by a mm or two) on either or both pinhole #1 and #3. This is OK. Penalty for being off center is a reduced field-of-view (4 arcsec/mm) and some added common path astigmatism. Small common path aberrations can be calibrated out later and are not of much concern. If off by more than a few millimeters, you may need recenter through pinhole #1 and tilt the parabola to center through pinhole #2, by using the screws on the back of its mount. Before tilting the parabola, check to see how far off center the alignment laser is on pinhole #3. If this is also off by more than a few millimeters, then tilting of the 1st parabola needs to be done as well as tilting the DM. WARNING: Only undertake tilting the 1st parabola and DM if absolutely necessary (i.e. things are very far off and you are sure there no other problems). It is very difficult to tilt the DM and small aberrations are preferable to the pain of changing this alignment or the chance of messing up the registration of the actuators with the subapertures.
  10. Align through pinhole #3.
    1. Open pinholes #1 and #2.
    2. Evaluate how far off center the spot is on pinhole #3. If off center by less than a couple millimeters and well aligned through pinhole #2, don't do anything else. Move 1st mirror after cass focus if you think you can get a reasonable compromise alignment through pinholes #1, #2, and #3. See note above about typical alignment.
    NOTE: Proper alignment through Pinhole #2 is most important. It is typical for the spot to be slightly off center on pinholes #1 and #3 (usually a millimeter or so high on #1 and a couple millimeters low on #3, if this is the case, don't bother moving either parabola or the DM tilt).
  11. Align to 1st Dichroic. Alignment laser should be below center on the 1st Dichroic, but centered on the turning mirror behind it. If necessary (shouldn't be if nothing has changed with respect to 1st parabola and DM tilt), tilt the 2nd parabola to steer beam to the center of the turning mirror behind the 1st Dichroic.
  12. Align through TT Cube pinhole.
    1. If only aligning for NGS mode and the mirror is in the 2nd Dichroic mount, move the 1st Dichroic so that the alignment laser is roughly centered on the mirror.
    2. If the dichroic is in the 2nd Dichroic mount, move the 1st Dichroic to center the beam through the TT Cube pinhole. This will, by default, put you well centered on the 2nd Dichroic.
  13. Align to center of WFS Steering mirror.
    1. Place the small paper target on the WFS Steering mirror.
    2. Move 2nd Dichroic to center alignment laser on the target.
    3. Remove target.
You should now be ready to do WFS Alignment and/or IRCAL initial alignment.


WFS Alignment

The goal here is to align the WFS optics to the beam line established by the alignment laser. Once that is done, the lenslet array is installed and internal WFS alignment is done to calibrate out any aberrations internal to the WFS. If all is in good shape, it will take an hour to do this procedure, but do not be surprised if it takes significantly longer.
  1. Record micrometer positions for all the optics in the WFS. While this isn't strictly necessary, it can be helpful if things go terribly awry and you need to get back to where you started.
  2. Remove all WFS optics. Make sure they all have locating blocks before you remove any of the optics! The lenslet array doesn't have a designated locating block, so you will have to move the WFS iris and use it as a locating block for the lenslet array.
  3. Move WFS Steering mirror to center laser on the active portion of the AOA WFS camera chip. The detector has two parts to it: a black part and a reflective part. The active area is the black part of the chip.
  4. Start real-time software if it is not already running.
  5. Turn off lights, darkness is required for the rest of this procedure.
  6. Do the following iterative procedure until spot is centered on AOA WFS camera crosshairs both with and without the 1st Reducing lens in.
    1. Adjust brightness of alignment laser so that WFS camera is not completely saturated.
    2. Insert 1st Reducing lens.
    3. Move 2nd Dichroic to center spot on WFS crosshairs.
    4. Remove 1st Reducing lens.
    5. Move WFS Steering mirror to center spot on WFS crosshairs.
  7. Install 1st Reducing lens if it isn't already in place.
  8. Install 2nd Reducing lens.
  9. Steer 2nd Reducing lens in X and Y to center spot on WFS crosshairs.
  10. Install Collimating lens.
  11. Steer in X and Y to center spot on WFS crosshairs.
  12. Install fiber chuck on the Iris stage.
  13. Move Iris stage to center fiber chuck on alignment laser.
  14. Insert RLS fiber in the fiber chuck.
  15. Collimate Collimating lens.
    1. Remove the filter wheel. This is necessary so there is enough room to put in the shear cube.
    2. Put the small shear cube between the Collimating lens and the lenslet array position.
    3. Move the Iris stage in Z (using the micrometer) until the fringes are parallel to the shear cube fiducial.
    4. Remove the shear cube.
    5. Install the filter wheel.
  16. Install Lenslet array.
  17. Make sure that real-time code is running with the quadcell centroider and using the scratch parameters. Also make sure that the hartmannModes are all zero.
    Type the following into CentDiag or TestRM:
    1. centquad
    2. sparms
    Zero all zernike modes in CentDiag or hartmannModes.
  18. Align lenslet array. Perform the following steps iteratively until all hartmann spots in the CentDiag display are within their inner circles at the highest magnification.
    1. Adjust brightness of RLS so that there are approximately 1000 to 2000 counts per subaperture on the CentDiag display.
    2. Center hartmann spots by moving 2nd Reducing lens X and Y. Use the CentDiag display to measure tip and tilt. Try to get both tip and tilt to be within +-0.05.
    3. Adjust Lenslet array rotation. Repeat the following until rotation is as close to 0.0 degrees as possible (usually to within a tenth of a degree).
      1. Take WFS Data
      2. Use aoIDL to measure WFS rotation. This program will calculate
      3. Turn goniometer the suggested amount
      4. Take more WFS Data, etc.
    4. Focus hartmann spots by adjusting CCD focus micrometer. This should be unnecessary since we are no longer changing to a different lenslet array for LGS mode. If it is necessary, do the following:
      1. Record the X and Y micrometer positions of the 2nd Reducing lens.
      2. Record the CCD Focus micrometer position.
      3. Steer 2nd Reducing lens in X and Y until the light for each hartmann spot is centered on a single pixel.
      4. Adjust the CCD Focus micrometer until you get the smallest spots possible. You may have to keep adjusting the X and Y position of the 2nd Reducing to keep the spots centered on a single pixel.
      5. If you get lost or confused, return to your starting point and try again (this is why you wrote down those micrometer positions).
    5. Center hartmann spots by moving 2nd Reducing lens X and Y.
    6. Adjust WFS magnification (should not be necessary unless something drastic has happened - standard position on micrometer is 4.060)
    7. Coarse Focus WFS
      1. Take an AOA camera cflat, i.e. turn off RLS and push the cflat button in the CentDiag window. Type cflat in the TestRM window.
      2. Change to the QuadCell centroider, i.e. type centquad into the CentDiag or TestRM window.
      3. Make sure that you are using scratch parameters, i.e. type sparms in CentDiag.
      4. Use the CentDiag display to measure the wavefront focus.
      5. Move Iris stage Z micrometer until Focus is close to 0.0, e.g. within +-0.005 (+-0.05).
  19. Fine WFS Alignment. Do the following iterative procedure until focus, tip, and tilt are all 0.0 (+- 0.01).
    1. Focus WFS: Move Iris stage Z until CentDiag focus is as close to 0.0 as possible (within a couple of hundreths).
    2. Center Spots: Move Iris stage X and Y until CentDiag tip and tilt are 0.0.
  20. Take Reference Centroids for all the algorithms
    For lgs7 type the following into CentDiag:
    1. refcent
    2. centcm
    3. sparms
    4. refcent
    5. centbin
    6. sparms
    7. refcent
    8. centcorr
    9. sparms
    10. refcent

    For lgs6 & lgs3:
    1. Type refcent in the TestRM window.
    2. Note the name of the new quadcell reference centroid file (listed in the StatRMttd window).
    3. Type centcm in the TestRM window, to change to the center of mass centroider.
    4. Type refcent in the TestRM window.
    5. Note the name of the new center of mass reference centroid file (listed in the StatRMttd window).
  21. Move WFS iris from being the lenslet locator block back to right in front of the WFS filter wheel.
  22. Close WFS iris. The hartmann spots making it through the iris should be close to the center of the WFS crosshairs (usually a row and/or column off from center. Note which spots are illuminated. Pointing and Centering adjustments later should cause the same hartmann spots to be illuminated when properly aligned through the iris stage iris and WFS optics.
  23. Open WFS iris.

Micrometer motions: To assist with aligning the WFS optics, the following table describes which micrometer does what and which direction to turn the micrometers for the desired effect. Many of these adjustments are unnecessary for typical alignment and listed for reference only.
EffectOpticMicrometer or AxisDirection
Steer spots left/right2nd Reducing Lens Perpendicular to AO benchLeft = CCW
Right = CW
Steer spots up/down2nd Reducing Lens Parallel to AO benchDown = CCW
Up = CW
Move intensity pattern left/rightCollimating Lens Perpendicular to AO benchRight = CCW
Left = CW
Move intensity pattern up/downCollimating Lens Parallel to AO benchUp = CCW
Down = CW
Rotate intensity patternLenslet Array

Coarse adjustment of focus/magnification of spots WFS Focus motorZ
"Blow out" spots2nd Reducing Lens Z
"Suck in" spots2nd Reducing Lens Z
Coarsely focus spots on CCDLenslet Array Z
Fine focus spots on CCDFocus stage under Lenslet Array Z

For reference, the micrometer positions for each WFS optic (NGS lenslet array, which, starting in 2002, is also used for LGS mode) are listed below. If after alignment the Strehl is not good (as measured on IRCAL) and the micrometer measures are very different from the following, there may be a problem. If the measured Strehl is good, then don't worry.

NGS WFS (2001 Oct 24)
Stage & AxisMicrometer Position
Iris Stage Z7.120
1st Collimating Lens X1.110
1st Collimating Lens Y3.468
1st Collimating Lens Z5.7001
Lenslet Array Goniometer7.8502
CCD Focus4.1862
Wavefront Focus4.0601
2nd Reducing Lens X6.200
2nd Reducing Lens y7.223
Notes:
1. These should not ever change.
2. These are significantly different from the current setup due to these components being disassembled and re-assembled after the October AO run.

Just in case we ever go back to using the LGS lenslet array the following table lists the micrometer positions (on 2001 Oct 24) so one can see the relative differences in the positions.

LGS WFS (on 2001 Oct 24)
Stage & AxisMicrometer Position
Iris Stage Z11.230
1st Collimating Lens X1.110
1st Collimating Lens Y3.468
1st Collimating Lens Z0.001
Lenslet Array Goniometer4.0752
CCD Focus2.6552
Wavefront Focus4.0601
2nd Reducing Lens X6.210
2nd Reducing Lens y7.378
Notes:
1. These should not ever change.
2. These are significantly different from the current setup due to these components being disassembled and re-assembled after the October AO run.


IRCAL Initial Alignment

Initial IRCAL alignment is simple and only takes a couple minutes.
  1. Connect the HeNe RLS or the battery powered laser to the alignment laser fiber.
  2. Adjust brightness of HeNe RLS to maximum if using it.
  3. If you followed the basic alignment directions, you should already be aligned to the center of the first mirror after the 1st Dichroic (1st IR mirror). If not, go back and check your basic alignment.
  4. Move the 1st IR mirror micrometers to center the alignment laser on the 2nd IR mirror.
  5. Make sure the dark cover is on IRCAL. It has two screws to ensure it is positioned correctly. On the center of the cover is a very hard to see crosshair.
  6. Move the 2nd IR mirror micrometers to center the alignment laser on the dark cover crosshairs.

Set Point Source Position

To properly set the point source position you will need to have IRCAL and its software running.
  1. Start the IRCAL software. For details see the IRCAL manual.
  2. Set all IRCAL filter wheels to Open (if the LickAO software isn't running, you should manually turn on the IRCAL motor controller power by pushing the appropriate pulizzi button before trying to move any motors).
  3. Take a short (1 second or so) exposure of the alignment laser.
  4. Note the center pixel position of the alignment laser spot. The spot will be very large, so make your best estimate of the center of the spot.
  5. Connect the RLS to the Point Source fiber.
  6. Take short exposure on IRCAL (1 second or less should do it).
  7. Move Fiber Stage motors in X and Y to put Point Source on same pixel as the center of the alignment laser spot (to within a few pixels).
  8. Iterate between taking exposures and moving the fiber stage until Point Source positioned properly.

Collimate Parabolas

  1. Install shear cube table.
    1. Unscrew IRCAL's vent tube (it gets in the way of the table).
    2. Install table above IRCAL. There is a screw and positioning block above IRCAL to make sure that the table is aligned properly.
    3. Make sure table is screwed on securely.
  2. Connect RLS (HeNe or battery powered laser) to Point Source fiber.
  3. Adjust HeNe RLS so it is at maximum brightness if using it.
  4. Collimate 1st Parabola.
    1. Set large shear cube on the installed table. Make sure the input port is facing the 1st parabola and is flush against the attached block. Have the fiducial screen facing up. The shear plate should intercept the center of the beam and be normal to the beam. If the shear plate is not normal to the beam, then you change the tilt of the fringes, which yields erroneous results.
    2. Adjust Fiber Stage Z micrometer so the fringes are parallel to the fiducial line on the screen.
    3. Rotate shear cube for fiducial screen is facing out (the most easily visible orientation).
    4. Evaluate the astigmatism and other aberrations. Typically, there will be about a half fringe of tilt. This is OK and no further adjustment is needed. For reference: At 532nm, 1 fringe of tilt = 1 mm of z-motion = 1 wave P-V of focus. 1 wave P-V of focus => spot from edge subaperture is 0.08 pixels displaced from the center of the quad-cell crosshairs, cf. approximately 0.5 pixel spot size. 1 waves of astigmatism = 30 arcsec off-axis on the sky = 8 mm off-axis parallel to table. Not-flat fringes indicate there is some surface figure in the mirror. There isn't anything you can do about it. With temperature changes, the mirror will change shape somewhat. It can take a day or two for it settle once on the telescope. Also, the focus can shift some from day-to-day; focus changes of several millimeters are not uncommon.
  5. Collimate 2nd Parabola.
    1. Connect RLS to fiber chuck in the iris stage so that light is propagating backwards through the AO system.
    2. Set large shear cube on the installed table so that it is propped up on the attached block. Make sure the input side is facing the 2nd parabola and the fiducial screen is facing up.
    3. Move WFS Focus stage until the fringes are parellel to the fiducial line.
    4. Rotate shear cube for fiducial screen is facing out (the most easily visible orientation).
    5. Evaluate the astigmatism and other aberrations. Typically there will be a quarter fringe of tilt. This is OK and can be calibrated out later. Alignment tolerances are about twice as loose for the 2nd parabola as for the first (linear dimensions only, due to the f/28 rather than f/17 focal ratio of the 2nd parabola). If there more than a fringe of astigmatism you might want to consider adjusting the tilt of the second parabola. Only embark on this procedure if you are sure there is nothing else wrong to cause the excessive astigmatism.
      1. Adjust WFS focus to flatten the fringes on top.
      2. Adjust tilt on the 2nd parabola (parallel to table only) so that the slope of the front fringes is cut in half.
      3. Repeat until the two orientation both give flat fringes.

IRCAL Pupil Alignment

This requires two people if AO is mounted on the telescope, one in the control room controlling the IRCAL and AO software and the other at the telescope moving mirrors and changing fiber connections. Communication is via the telex headsets. When in the AO lab, everything can be run by a single person.

This process can take anywhere from 15 minutes to an hour to perform.

  1. Connect RLS to the Point Source Fiber.
  2. Put Fiber stage at Red Light Source position.
  3. Make sure IRCAL software is running.
  4. Make sure tip/tilt mirror is in the E-Null position.
  5. Put all IRCAL filter wheels in the Open position.
  6. Repeat the following until the spot is centered on IRCAL:
    1. Take image on IRCAL. 100ms to 1000ms exposure time depending on brightness of the HeNe laser.
    2. Use fhwm tool on IRCAL Image Browser to determine spot centroid position.
    3. Manually move 1st IRCAL turning mirror in x and y to center spot on IRCAL. A 1/4 chip move is approximately 5 tics on the micrometers.
  7. Move the Fiber stage to LGS Simulator position.
  8. Change RLS fiber from Point Source to 200micron source.
  9. Turn up brightness of RLS laser.
  10. Repeat the following until the central obscuration on IRCAL is centered.
    1. Take image on IRCAL. 100ms to 1000ms exposure times are typical, depending on RLS brightness.
    2. Manually move 2nd IRCAL turning mirror in x and y to center obscuration on IRCAL. A typical move is 3 tics on the micrometer. The pattern is often difficult to interpret, so use your best judgement on when the central obscuration is truly centered.
  11. Repeat this entire procedure until pointing and central obscuration centering is good. Be forewarned that this is an iterative and somewhat tedious process.

WFS Pointing and Centering

This procedure adjusts the positions of the 2nd Dichroic and WFS steering mirror so that incoming light is properly aligned into the WFS.
  1. Connect RLS to the Point Source fiber.
  2. Adjust brightness of RLS until there are approximately 2500 to 3000 counts per subaperture on the CentDiag display.
  3. Make sure Tip/Tilt Mirror is on and in E-Null position .
  4. Make sure you are in the QuadCell centroider.
    For lgs7 type the following into CentDiag:
    1. centquad
    For lgs6 & lgs3 type the following into TestRM:
    1. centquad
    2. cparm MMMDD_XX where MMMDD_XX refers to the name of the current reference centroids for the quad cell centroider, e.g. Apr01_00
  5. Open P & C window in LickAO software.
  6. Turn P & C motors on.
  7. Repeat the following until Pointing and Centering looks good. Please note that changing pointing can change the centering, and that centering adjustments almost certainly will change the pointing a little bit.
    1. Adjust Pointing to best center the spots on the AOA WFS camera crosshairs. Use CentDiag tip and tilt numbers to evaluate how well centered the spots are. NGS WFS plate scale is 2 arcseconds per pixel. LGS WFS plate scale is 4 arcseconds per pixel. Note: We no longer use the LGS lenslet array, we now use the NGS lenslet array for both NGS and LGS observing.
    2. Adjust Centering to best evenly illuminate all subapertures. Note that there is often a gradient in the illumination pattern, so do your best to account for it when deciding how to adjust the centering. A typical large centering adjustment is 10 Renishaw encoder counts. A small adjustment is 3 counts.
  8. When finished, call those positions zero in the Motor Status window of LickAO and reset the cummulative offsets for the P & C mirrors.

IRCAL Focus

IRCAL focusing typically takes 10 minutes or so to perform.
  1. Move Fiber stage to White Light Source position.
  2. Turn on White Light Source. Adjust brightness so that there are 2000 to 3000 counts per subaperture.
  3. Turn on relay to allow NGS control of Tip/Tilt Mirror.
  4. Turn on DM 100V power supply.
  5. Close TT Loop.
  6. Adjust Centering if necessary. This should not be necessary if you just adjusted the Pointing and Centering, as described above.
  7. Close AO Loop.
  8. Make a new mirror flat. This is not a necessary step, but makes miscellaneous adjustments and calibrations to the system easier.
    For lgs7 type the following into CentDiag:
    1. msharp
    2. sharpen to apply the shape to the mirror when the loop is open.
    For lgs6 & lgs3:
    1. Take WFS data.
    2. Note the new diagnostic file name.
    3. Log onto lgs6 as lgs.
    4. On lgs6 type cd Data/MirrorData
    5. On lgs6 type mkOffsetFile
    6. You will be prompted for the diagnostic file name parts.
    7. You should now have a new mirror flat file.
  9. Put in IRCAL's Br-Gamma filter.
  10. Set auto fwhm in IRCAL Image Browser.
  11. Take an exposure (200ms x 5 coadds is a typical exposure time).
  12. Put IRCamFocus number in the focval box in Image Browser.
  13. Press "focfit init" button if first focus measurement, otherwise press "focfit" button.
  14. Adjust IRCamFocus (steps of 5000 counts are typical, move in positive direction or do backlash compensation if going to lower focus values).
  15. Repeat entire procedure and set IRCamFocus to best focus value determined by focfit program.

Image Sharpening

Procedure is the same as for IRCAL Focus, except do for each mode in the CentDiag Hartmann Slider GUI or hartmannMode GUI. Typical step size is 5 for all modes or 5 for modes 2 through 7, 10 for modes 8 through 10. Mode 1 is not adjusted and should always be left at 0.


Daily NGS Afternoon Alignment

  1. Exit ircalui, move data using the ircalcopy script, and restart ircalui.
  2. Turn on TT 100V, DM 100V, and motor 24V power supplies.
  3. Turn on red laser source (RLS).
  4. Take a short exposure on IRCAL (all filters in the Open position) to verify that RLS is in the central half of the chip.
  5. If the RLS is more than about 50 pixels off in the N-S direction on the chip, move the fiber stage Y to bring RLS reasonably near center. If RLS is more than a few pixels off in the E-W direction, the first IRCAL steering mirror may have been bumped when the dewar was filled. Check micrometers (proper positions for these mirror micrometers should have been recorded during initial alignment).
  6. Use the rlsPosition script from ircalui to automatically center the fiber stage. Before starting the script, make sure filters are open, exposure is appropriate, and auto fwhm is turned on in ircaldisplay. When the script has completed (RLS should be very near (128,128)), call fiber X and Y stages zero and note the Renishaw position for each.
  7. Make sure that you have a current cflat and NGS control matrix for the WFS.
  8. Adjust WFS Pointing and Centering (P&C) until RLS well aligned on WFS. WFS Tip and Tilt readings should be small, e.g. +-0.1 with the TT mirror at E-Null.
  9. Close TT loop.
  10. Take exposure on IRCAL and measure position of RLS. Adjust P&C until RLS hits same spot on IRCAL as it did with the mirror at E-Null. Also make sure that the RLS centering is good. You will probably have to iterate between adjusting Pointing and Centering.
  11. Call P&C motor positions zero and reset the cumulative values.
  12. Put in White Light Source (WLS). Adjust fiber Y to bring Tip in centDiag near 0.
  13. It is best to have over 1500 counts per subaperture for the following steps. It is ok to run at a slower rate (e.g. 200 Hz) if necessary. Make sure you have a good cflat for whatever rate you use. Typically use AO gain of 0.5 and TT gain of 1.0. Typical exposure time of 200ms with 10 coadds using the Br-Gamma filter in IRCAL.
  14. Close TT and AO loops. Adjust WLS centering if necessary.
  15. Use the imageSharpen2 script in ircalui to focus and image sharpen. When finished, record Hartmann modes.

Elinor Gates and Brian Bauman

Last update: 23 November 2002