PEPSIPOL AGW3/4 alignment UT 20190120

OSA: J. C. Williams (LBTO)

Observers/ISA: J. Hill (Tucson) plus team PEPSI on the mountain

Software: S. Hooper/P. Kubanek (on-call)

ISp:G. Bechetti

Mtn Manager: M. Wagner

Summary

PEPSIPOL activities in twilight prior to an ARGOS night:

  • We were able to collimate both sides on-axis using IDL active optics. GCS active optics diverged.

  • With only two examples, we had problems hitting the off-axis guide stars (maybe an issue in the X-direction? or maybe slight errors in rotator zeropoints?)

  • IDL had incorrect pupil shift directions for off-axis collimation. I think I have fixed that after the fact.

Still to be done:

  • Try IDL off-axis collimation again with the new parameters.

  • Try to fix GCS on-axis collimation - John is working this offline tonight, and has corrected at least one parameter that seemed to be wrong.

  • Correct the 11 mm of AGW4 probe position with an offset in the preset (PCS configuration). Need to figure out the proper DETXY coords of the correction as I know it in native AGW.

  • Check polarimeter alignment relative to N-S using binary stars.

Details

00:48 UT - Stop and restart both GCS to absorb configuration changes about angles, lenslet_rotations and X-flip. There's still a mystery why PEPSIPOL_L has pointing and guiding X-flips, but PEPSIPOL_R does not.

initial pointing

00:50 UT - ACQUIRE preset to M5 star while waiting for it to get dark enough.

01:01 UT - guide cameras no longer saturated in 200 millisec exposure (2x2 binning) with clear sky (~11 mag on SkyB plot).

01:09 UT SX IE -22.30000 CA -3.00000
DX IE 4.00000 CA 29.00000

01:12 UT - ACTIVE preset didn't find 12 mag star - too bright ?

01:16 UT - ACQUIRE preset on-axis to 7.5 mag star

collimation

01:23 UT - ACTIVE on-axis to 7.5 mag star. GCS collimation diverged on both sides. IDL seemed to be converging on left, but this star is too bright.

01:29 UT - ACTIVE on-axis to 11.7 IDL collimation succeeds on both sides.

01:36 UT - resend same ACTIVE on-axis preset to try GCS again when better collimated. GCS runs away in Z6 on Left. Right side is guiding off to the side, but collimation looks OK - guiding issues likely because we are at EL=85.5 (maybe there was coma runaway at the end?). right_wfscimage000031.fits is an example where GCS seems to have problems - see more detailed analysis below.

01:41 UT - ACTIVE preset off-axis X=-46.1, y=515.7 - no star found, and sky is plenty dark enough.

01:44 UT - ACTIVE preset off-axis with different guide star x=-1.7 y=456.2 collimating with IDL, but it didn't send zern at first. Could the X-direction of the guide probe be wrong? Pupil shift for Y-direction is wrong for IDL - still at EL=84.

01:52 UT - same preset - missed right guide star. GCS pupil shift looks correct on left. Need to fix IDL pupil shift before getting a good comparison with GCS. Lenslet_rotation looks OK on both sides (with values I updated this afternoon from the LFBG work).

Pupil shifts are transposed in IDL compared to GCS (both sides)......
Pupil Shift = -29.69 -0.43 -0.43 29.69

01:54 switch back to ARGOS, sharing the switchover time across 18-deg twilight fairly evenly.

offline analysis

IDL pupil shifts

02:04 UT - Try r_pupil_shift -0.19 for LPOL - no that wasn't it. Put it back to normal 0.19.

02:10 UT - wfsc.xy_transpose = 0 (rather than 1) fixes the transposition, but not the sign.
Pupil Shift = -0.43 -29.69 -0.43 29.69

02:14 UT - x_pupil_shift_direction = 1.0 (rather than -1)
Pupil Shift = 0.43 -29.69 -0.43 29.69

02:17 UT - try r_pupil_shift -0.19 for LPOL again in combination with x_pupil_shift_direction = 1.0 wfsc.xy_transpose = 0
Pupil Shift = -0.43 29.69 -0.43 29.69
Now matching GCS - without a careful measurement of the X-shift.

02:25 UT - applied those same values to RPOL, so now IDL has the same pupil shift as GCS.

GCS on-axis collimation

Here's the RPOL on-axis example (below) where GCS collimation is diverging. It looks like the problem is in the positioning of the lenslet grid. Note the line "X,Y Average Removed" which should not be as large as -0.6. Yesterday I had transformed Doug's lenslet_x_center coords to GCS space by adding 8.5 * lenslet spacing = 113 pixels. My note on IT 7388 indicates that we got AGW4@LFBG working by using an offset of integer lenslet spacings rather than half-integer lenslet spacings (transforming from the LL corner of lenslet 0,0 to the lower left corner of lenslet 8,8), so I'm going to try that next (107 pixels rather than 113).

What we were using on RPOL tonight (20190120 UT):
WFScam_hotspot_x        150.0           double  # ccd x coordinate of pixel that represents x-center of WFS spots (20190181 DLM)
WFScam_hotspot_y        235.0           double  # ccd y coordinate of pixel that represents y-center of WFS spots (20190118 DLM)
WFScam_ROI              "1 1 512 512"   string  # full frame ROI if different from AzCam initialization, X1 Y1 X2 Y2  SetROI 1 512 1 512 1 1
WFScam_hotspot_sext_x   157.0           double  # ccd x coordinate of pixel that represents lower leftmost x-center of WFS spots (20120204 DLM)
WFScam_hotspot_sext_y   217.0           double  # ccd y coordinate of pixel that represents lower leftmost y-center of WFS spots (20120204 DLM)
while IDL was using:
            agw_params[i].wfsc.pupil_x_on_axis = 150.0  ; DLM 20190118          
            agw_params[i].wfsc.pupil_y_on_axis = 235.0  ; DLM 20190118          

            agw_params[i].wfsc.lenslet_x_center = 45.0  ; DLM 20190118          
            agw_params[i].wfsc.lenslet_y_center = 117.0 ; DLM 20190118   


IDL> wfsc_process_file, '/Repository/20190120/GCS/right_wfscimage000031.fits'
Changing sign of Zernikes 5, 8 and 10 for AGw3/AGw4
 
  => File: /Repository/20190120/GCS/right_wfscimage000031.fits
  => Date: 2019-01-20
  => Time: 01:32:41.121
  => Instrument: RPOL @ RPOL
  => Elevation: 85
  => Azimuth: 161
 
  =>  Cow Reconstructor: Recalculated
  => Sext Reconstructor: Recalculated
 
                           ........... IDL ...................... GCS ....
  => AGW Parameters: 
        Guide Probe X =                -0.01                      -0.01
        Guide Probe Y =                -0.01                      -0.01
 
  => Zernike Rotation:
      Rotation Offset =               124.00                     124.00
        Rotator Angle =        (-)    207.04              (-)    207.04
                              ---------------            ---------------
         Doug`s Angle =               -83.04                     -83.04
        WFSC Rotation =        (-)      0.00              (-)      0.00
                              ---------------            ---------------
       Total Rotation =               -83.05                     -83.05
 
  => Primary Coordinates:
           X Position =                -0.00                       0.01
           Y Position =                -0.02                      -0.02
          Field Delta =               -90.00                     -90.00
          Field Angle =               360.00                     360.00
   
  => Pupil Positioning:              X       Y                   X       Y
        On-Axis Pupil =           150.00  235.00              150.00  235.00
          Pupil Shift =             0.00    0.00                0.00    0.00
 Shifted Pupil Center =           150.00  235.00
                                  --------------              --------------
         Pupil Center =           145.35  230.73              163.69  237.07
     
  => Shack-Hartmann Results:
       SH Spots Found =                113                          115
        SH Spots Used =                 62                           54
          Subaps Used =                 62                           68
   Background Removed =                665                          658
  X,Y Average Removed =          -0.3457  0.2374               0.2410 -0.6050
             FWHM Ave =           0.91" +- 0.08"               0.92" +- 0.09"
      Ellipticity Ave =           0.15  +- 0.07                0.16  +- 0.07
      Ellipticity Sum =           0.10 @  36 degrees           0.00 @   0 degrees
    SExtractor Method = Center-of-Weight
     
                               ........ IDL .......            .... GCS ....
  => RMS Wavefront Error:  ... Sext ........... Cow ............... Sext ....
    Hex:     Z[4,5,6] =        1152             612                3777
    Med:       Z[7,8] =        2284            1557                2698
    Low:      Z[4-11] =        2560            1673                6711
   High:     Z[12-22] =         291             234                 306
    All:      Z[4-22] =        2577            1690                6718
  => Sent (PSF Factor: 0.8, Med Factor 0.3):
    Hex: Z[4,5,6,7,8] =        1072                                5369
    Low:      Z[4-11] =                        1339
  
                                              Rotated                  Field                                        Scaled to
                   Raw Zernikes              to Primary              Correction               Total                Send to PSF
  Zern #        sext   cow    GCS       sext   cow    GCS       sext   cow    GCS       sext   cow    GCS       sext   cow    GCS
  ---------------------------------------------------------------------------------------------------------------------------------------------
  Z[ 2] =        47     -5    -57   
  Z[ 3] =      -108     -5    488   
  Z[ 4] =     -1278   -664   2290      1022    531  -2519                              1022    531  -2519       818    425  -2015
  Z[ 5] =       527   -306   2055       487   -194  -2305         0      0      0       487   -194  -2305       390   -155  -1844
  Z[ 6] =      -404   -228  -2357      -213   -236  -1615         0      0      0      -213   -236  -1615      -170   -188  -1292
  Z[ 7] =      2242   1541   1066     -1187   1093  -2413         0      0      0     -1187   1093  -2413      -285    875   -579
  Z[ 8] =     -1768   1189  -2340     -1952  -1108   1207         0      0      0     -1952  -1108   1207      -468   -887    290
  Z[ 9] =        14    -31  -3060       -27      6  -3435                               -27      6  -3435         0      5      0
  Z[10] =       -42     20  -2918       -22     29  -1638                               -22     29  -1638         0     23      0
  Z[11] =      -119    -18   3335        95     14  -3001                                95     14  -3001         0     12      0
  Z[12] =      -111    -99    462       -99     95      0                               -99     95      0         0      0      0
  Z[13] =      -142   -166   1847       -78     96      0                               -78     96      0         0      0      0
  Z[14] =      -162    -52    336       132    -64      0                               132    -64      0         0      0      0
  Z[15] =       -98    -99    618         8    -45      0                                 8    -45      0         0      0      0
  Z[16] =       184    192    644        25    -75      0                                25    -75      0         0      0      0
  Z[17] =        58    131    589      -132    145      0                              -132    145      0         0      0      0
  Z[18] =        30    -17    178       -32     32      0                               -32     32      0         0      0      0
  Z[19] =        60     43    307        35      1      0                                35      1      0         0      0      0
  Z[20] =       -44    -32  -1824        21    -44      0                                21    -44      0         0      0      0
  Z[21] =         7     55   2422        22      4      0                                22      4      0         0      0      0
  Z[22] =      -247    -40    874       173     28   -306                               173     28    -92         0      0      0
 tmp_pixels =          328
      4352.54

-- JohnHill - 20 Jan 2019
Topic revision: r1 - 20 Jan 2019, JohnHill
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