[Comm2011] Fwd: PPRS-041986-Updated-VST-CASSEGRAIN ROTATOR-Strong rotation pattern in OmegaCAM images aorund meridian-Instrumentation
Konrad Kuijken
kuijken at strw.leidenuniv.nl
Thu Oct 6 08:20:12 CEST 2011
Begin forwarded message:
> From: Paranal_AREmail <esoarspl at eso.org>
> Subject: PPRS-041986-Updated-VST-CASSEGRAIN ROTATOR-Strong rotation pattern in OmegaCAM images aorund meridian-Instrumentation
> Date: October 6, 2011 5:38:45 GMT+02:00
> To: kuijken at strw.leidenuniv.nl
> Reply-To: Paranal_AREmail <esoarspl at eso.org>
>
> Problem number PPRS-041986 in the Paranal PRS has now been updated.
> The new details of the ticket are listed below.
> This is for your information only.
>
>
> Problem Number : PPRS-041986
>
> Creation Date : 2011-10-04 04:00:47 by Steffen Mieske (vst at eso.org)
> Type : Problem
> Keywords : Strong rotation pattern in OmegaCAM images aorund meridian
> Priority : Critical
> Deadline :
> Status : Assigned
>
> ----- Minor Change Section ---------------------
>
> -------------------------------------------------
>
> Location : VST
> Area/Instrument Type : TELESCOPE
> System/Instrument : CASSEGRAIN ROTATOR
> Sub-system :
>
> Assigned to Group : Instrumentation
> Assigned to Person : mriquelm
> CC List :
> andrea.baruffolo at oapd.inaf.it
> par-tios at eso.org
> uweilenm at eso.org
> msterzik at eso.org
> vst at eso.org
> par-vst at eso.org
> acarlier at eso.org
> akaufer at eso.org
> jspyromi at eso.org
> kuijken at strw.leidenuniv.nl
> pietro.schipani at oacn.inaf.it
>
> Telescope Downtime : 01:45
> Workload (hrs.) : 0
> Detailed Description :
> Dear Instrumentation team,
>
> tonight we experienced a sudden strong degradation of Image quality while crossing the meridian at around 82 degrees altitude. The IQ would degrade by 30-40% in a ring toward the outer part of the FOV. Please have look at the PSF anisotropy maps by doing
>
> firefox /diska/home/astro/awehome/cache/OMEGACAM_IMG_OBS277_005*psfanisotropy.png
>
> from a wocoff xterm.
>
>
> The affected time range is UT 03:00 to 03:15. Before and after this the IQ distribution is more or less OK. Here a list of the images taken around that time, the two most affected ones are 0055 and 0056.
>
> wocoff astro:/data/raw/2011-10-03 1040 > dfits *005*fits | fitsort ADA.ABSROT.START ADA.ABSROT.END ORIGFILE ARCFILE TEL.ALT TEL.AZ
> OMEGACAM_IMG_OBS277_0050.fits 128.18119 132.05155 OMEGACAM_IMG_OBS277_0050.fits OMEGA.2011-10-04T02:31:17.696.fits 79.951 312.336
> OMEGACAM_IMG_OBS277_0051.fits 133.04768 137.65534 OMEGACAM_IMG_OBS277_0051.fits OMEGA.2011-10-04T02:41:18.952.fits 80.847 316.573
> OMEGACAM_IMG_OBS277_0052.fits 138.14856 143.50017 OMEGACAM_IMG_OBS277_0052.fits OMEGA.2011-10-04T02:46:00.635.fits 81.564 321.156
> OMEGACAM_IMG_OBS277_0053.fits 144.04696 150.35415 OMEGACAM_IMG_OBS277_0053.fits OMEGA.2011-10-04T02:50:44.328.fits 82.206 326.548
> OMEGACAM_IMG_OBS277_0054.fits 151.67927 158.75065 OMEGACAM_IMG_OBS277_0054.fits OMEGA.2011-10-04T02:55:28.031.fits 82.701 333.606
> OMEGACAM_IMG_OBS277_0055.fits 159.82803 167.64855 OMEGACAM_IMG_OBS277_0055.fits OMEGA.2011-10-04T03:00:13.294.fits 83.096 341.216
> OMEGACAM_IMG_OBS277_0056.fits 171.36590 178.62316 OMEGACAM_IMG_OBS277_0056.fits OMEGA.2011-10-04T03:10:01.369.fits 82.470 352.136
> OMEGACAM_IMG_OBS277_0057.fits 179.58848 186.89678 OMEGACAM_IMG_OBS277_0057.fits OMEGA.2011-10-04T03:14:45.942.fits 82.569 359.773
> OMEGACAM_IMG_OBS277_0058.fits 187.73194 194.83066 OMEGACAM_IMG_OBS277_0058.fits OMEGA.2011-10-04T03:19:26.015.fits 82.526 7.366
> OMEGACAM_IMG_OBS277_0059.fits 195.67887 199.70319 OMEGACAM_IMG_OBS277_0059.fits OMEGA.2011-10-04T03:24:09.918.fits 82.248 14.739
>
> OMEGACAM_IMG_OBS277_0052.fits 138.14856 143.50017 OMEGACAM_IMG_OBS277_0052.fits OMEGA.2011-10-04T02:46:00.635.fits
> OMEGACAM_IMG_OBS277_0053.fits 144.04696 150.35415 OMEGACAM_IMG_OBS277_0053.fits OMEGA.2011-10-04T02:50:44.328.fits
> OMEGACAM_IMG_OBS277_0054.fits 151.67927 158.75065 OMEGACAM_IMG_OBS277_0054.fits OMEGA.2011-10-04T02:55:28.031.fits
> OMEGACAM_IMG_OBS277_0055.fits 159.82803 167.64855 OMEGACAM_IMG_OBS277_0055.fits OMEGA.2011-10-04T03:00:13.294.fits
> OMEGACAM_IMG_OBS277_0056.fits 171.36590 178.62316 OMEGACAM_IMG_OBS277_0056.fits OMEGA.2011-10-04T03:10:01.369.fits
> OMEGACAM_IMG_OBS277_0057.fits 179.58848 186.89678 OMEGACAM_IMG_OBS277_0057.fits OMEGA.2011-10-04T03:14:45.942.fits
> OMEGACAM_IMG_OBS277_0058.fits 187.73194 194.83066 OMEGACAM_IMG_OBS277_0058.fits OMEGA.2011-10-04T03:19:26.015.fits
> OMEGACAM_IMG_OBS277_0059.fits 195.67887 199.70319 OMEGACAM_IMG_OBS277_0059.fits OMEGA.2011-10-04T03:24:09.918.fits
>
>
> Together with the azimuth offsets consistently failing around this region (PPRS 041851), we may be facing a serious issue here.
>
>
> Thanks,
> Steffen
>
> ----- Worklog & Comments Section ---------------
>
> Worklog and Comments :
> 2011-10-04 11:32:55 joneal
> Assignee changed: mriquelm
> Status Changed: Assigned
> Modified By: joneal
> Modified Date: 2011-10-04 11:32:55
> Assignee changed: mriquelm
> Status Changed: Assigned
> Modified By: joneal
> Modified Date: 2011-10-04 11:32:55
> 2011-10-04 20:59:35 vst
> I copy&paste the ocam log of the aberration corrections sent during the affected time. No peculiar aberration measured during that time.
>
> I also include Andrea Barrufolo in CC. Andrea, how would the 2 star guiding react to a residual rotation introduced by the VST rotator?
>
> Oct 4 02:50:03 wocam seqWish: 2011-10-04 02:50:03.964204 wocam seq bob_21460 199 0 about to send WRTABER 0 15.2 0.0 0 0 -112.6 0 -50.1 0 0 -10.2 0 0.0 0 0 0 0 0, 0 0 0 0 0 141.2 0 14.6 0 0 11.4 0 0.0 0 0 0 0 0
> Oct 4 02:50:10 wocam seqWish: 2011-10-04 02:50:10.368627 wocam seq bob_21460 199 0 WRTRABER returned 0
> Oct 4 02:54:46 wocam seqWish: 2011-10-04 02:54:46.813276 wocam seq bob_21460 199 0 about to send WRTABER 0 1.6 0.0 0 0 -217.6 0 -35.7 0 0 -12.0 0 0.0 0 0 0 0 0, 0 0 0 0 0 -29.4 0 -55.3 0 0 147.8 0 0.0 0 0 0 0 0
> Oct 4 02:54:53 wocam seqWish: 2011-10-04 02:54:53.244474 wocam seq bob_21460 199 0 WRTRABER returned 0
> Oct 4 02:59:32 wocam seqWish: 2011-10-04 02:59:32.596885 wocam seq bob_21460 199 0 about to send WRTABER 0 10.0 0.0 0 0 -38.7 0 -47.1 0 0 -17.0 0 0.0 0 0 0 0 0, 0 0 0 0 0 34.8 0 -108.0 0 0 74.2 0 0.0 0 0 0 0 0
> Oct 4 02:59:36 wocam seqWish: 2011-10-04 02:59:36.001536 wocam seq bob_21460 199 0 WRTRABER returned 0
> Oct 4 03:04:15 wocam seqWish: 2011-10-04 03:04:15.865658 wocam seq bob_21460 199 0 about to send WRTABER 0 126.6 0.0 0 0 -219.2 0 -66.8 0 0 -11.4 0 0.0 0 0 0 0 0, 0 0 0 0 0 47.4 0 -79.3 0 0 16.0 0 0.0 0 0 0 0 0
> Oct 4 03:04:22 wocam seqWish: 2011-10-04 03:04:22.297129 wocam seq bob_21460 199 0 WRTRABER returned 0
> Oct 4 03:14:03 wocam seqWish: 2011-10-04 03:14:03.788125 wocam seq bob_21460 199 0 about to send WRTABER 0 -56.6 0.0 0 0 -42.9 0 -36.7 0 0 -29.2 0 0.0 0 0 0 0 0, 0 0 0 0 0 102.1 0 -174.4 0 0 161.2 0 0.0 0 0 0 0 0
> Oct 4 03:14:10 wocam seqWish: 2011-10-04 03:14:10.196940 wocam seq bob_21460 199 0 WRTRABER returned 0
> Oct 4 03:18:48 wocam seqWish: 2011-10-04 03:18:48.556040 wocam seq bob_21460 199 0 about to send WRTABER 0 12.9 0.0 0 0 -110.0 0 -17.6 0 0 -26.9 0 0.0 0 0 0 0 0, 0 0 0 0 0 -177.0 0 -2.4 0 0 -120.7 0 0.0 0 0 0 0 0
> Oct 4 03:18:52 wocam seqWish: 2011-10-04 03:18:52.954627 wocam seq bob_21460 199 0 WRTRABER returned 0
> 2011-10-05 05:00:33 vst
> Tonight we experienced again this strong residual rotation, amounting to about 5 pixels during a 4 min integration at the edge of the FOV. The effect starts to become notable in our case at about 25-30 min before meridian crossing, for an observation which reached a maximum altitude of 83 degrees at meridian.
>
> We made tests with single and double star guiding. With single star guiding, the region close to the single guide star remains more or less still, and the rotation is more or less around that single guide star.
>
> For double star guiding, the rotation pattern is tyically pointsymmetric to the center of the FOV. In both cases, the IQ degradation due to the rotation is, as written above, very strong of order 1".
>
> I elevate this to critical.
>
> Below more details. Until 04:00 UT these were two OB executions with two star guiding. After 04:00 UT is an execution with a single guide star, with a starting rotator angle similar to the previous executions.
>
> First is the list of IQ, note the IQ_degr. Below that is the list of images with rotator angles etc.
>
> Finally, I have transfered the anisotropy maps taken during that time to vst at odyssey4:smieske_mod and will send them to Pietro Schipani and Konrad Kujken via email.
>
>
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------
> Date OBid Filter | ImaQuality Ellipticity | N_Ell | MeanIQ | IQ_degr | MeanELL | N_reduced
> | Chip65 Chip76 Chip85 Chip96 | | Ima OB/F | Ima OB/F | Ima OB/F |
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> 2011-10-05T03:12:20.487 581565 i_SDSS 0.62 0.06 0.53 0.04 0.56 0.04 0.62 0.07 0 0.58 1.12 0.05 8
> 2011-10-05T03:17:05.209 581565 i_SDSS 0.63 0.06 0.52 0.04 0.64 0.05 0.70 0.08 0 0.60 1.15 0.06 8
> 2011-10-05T03:21:47.532 581565 i_SDSS 0.69 0.04 0.52 0.06 0.53 0.07 0.70 0.05 0 0.61 1.32 0.06 8
> 2011-10-05T03:26:31.335 581565 i_SDSS 0.69 0.04 0.53 0.05 0.55 0.06 0.73 0.04 0 0.63 1.35 0.06 8
> 2011-10-05T03:31:13.678 581565 i_SDSS 0.85 0.08 0.56 0.07 0.56 0.08 0.77 0.08 0 0.70 1.48 0.09 8
> 2011-10-05T03:41:38.524 581565 i_SDSS 0.68 0.09 0.51 0.11 0.54 0.11 0.95 0.19 1 0.69 1.60 0.13 8
> 2011-10-05T03:46:19.987 581565 i_SDSS 0.95 0.17 0.49 0.05 0.79 0.08 0.91 0.09 0 0.75 1.60 0.10 8
> 2011-10-05T03:51:03.980 581565 i_SDSS 0.76 0.17 0.57 0.10 0.66 0.10 0.90 0.12 0 0.71 1.38 0.12 8
> 2011-10-05T03:55:48.473 581565 i_SDSS 0.57 0.09 0.58 0.10 0.61 0.09 0.90 0.11 0 0.63 1.16 0.09 8
> 2011-10-05T04:00:33.125 581565 i_SDSS 0.56 0.09 0.47 0.06 0.46 0.05 0.78 0.10 0 0.56 1.38 0.07 8
> 2011-10-05T04:18:38.716 581565 i_SDSS 1.10 0.21 0.73 0.09 0.64 0.07 0.65 0.08 1 0.79 1.30 0.11 8
> 2011-10-05T04:23:24.289 581565 i_SDSS 0.69 0.11 0.60 0.06 0.57 0.04 0.72 0.10 0 0.64 1.19 0.08 8
> 2011-10-05T04:28:04.872 581565 i_SDSS 1.79 0.29 0.79 0.12 0.67 0.08 0.69 0.09 2 0.96 1.63 0.14 8
> 2011-10-05T04:32:48.665 581565 i_SDSS 1.43 0.39 0.94 0.27 0.80 0.21 0.83 0.14 7 1.00 1.31 0.26 8
> 2011-10-05T04:37:32.437 581565 i_SDSS 2.58 0.41 1.42 0.22 0.99 0.13 0.93 0.14 3 1.48 0.76 1.48 1.36 0.23 0.11 8
>
>
> FILE ADA.ABSROT.START ADA.ABSROT.END TEL.PARANG.START TEL.PARANG.END DATE-OBS
> OMEGACAM_IMG_OBS278_0001.fits 110.49936 112.10833 -69.453 -67.842 2011-10-05T02:40:57.268
> OMEGACAM_IMG_OBS278_0002.fits 112.22919 114.00605 -67.714 -65.932 2011-10-05T02:45:44.191
> OMEGACAM_IMG_OBS278_0003.fits 114.13537 116.06165 -65.803 -63.871 2011-10-05T02:50:24.614
> OMEGACAM_IMG_OBS278_0004.fits 116.60931 118.78075 -63.323 -61.146 2011-10-05T02:55:08.426
> OMEGACAM_IMG_OBS278_0005.fits 119.16396 121.56444 -60.771 -58.355 2011-10-05T02:59:49.099
> OMEGACAM_IMG_OBS278_0006.fits 123.01324 126.23083 -56.890 -53.663 2011-10-05T03:12:20.487
> OMEGACAM_IMG_OBS278_0007.fits 126.55547 130.28839 -53.351 -49.593 2011-10-05T03:17:05.209
> OMEGACAM_IMG_OBS278_0008.fits 130.67843 134.99884 -49.184 -44.886 2011-10-05T03:21:47.532
> OMEGACAM_IMG_OBS278_0009.fits 135.98795 141.10800 -43.858 -38.766 2011-10-05T03:26:31.335
> OMEGACAM_IMG_OBS278_0010.fits 141.97007 147.78661 -37.880 -32.073 2011-10-05T03:31:13.678
> OMEGACAM_IMG_OBS278_0011.fits 157.66749 165.31345 -22.136 -14.472 2011-10-05T03:41:38.524
> OMEGACAM_IMG_OBS278_0012.fits 166.22350 174.42180 -13.560 -5.322 2011-10-05T03:46:19.987
> OMEGACAM_IMG_OBS278_0013.fits 175.38152 183.99390 -4.394 4.221 2011-10-05T03:51:03.980
> OMEGACAM_IMG_OBS278_0014.fits 185.24729 193.49301 5.505 13.681 2011-10-05T03:55:48.473
> OMEGACAM_IMG_OBS278_0015.fits 194.52127 199.66569 14.708 0.000 2011-10-05T04:00:33.125
> OMEGACAM_IMG_OBS278_0016.fits 143.79050 149.89131 -36.056 -29.915 2011-10-05T04:18:38.716
> OMEGACAM_IMG_OBS278_0017.fits 150.61490 157.68455 -29.215 -22.100 2011-10-05T04:23:24.289
> OMEGACAM_IMG_OBS278_0018.fits 158.47231 166.21013 -21.340 -13.557 2011-10-05T04:28:04.872
> OMEGACAM_IMG_OBS278_0019.fits 167.53416 175.85983 -12.265 -3.905 2011-10-05T04:32:48.665
> OMEGACAM_IMG_OBS278_0020.fits 177.07371 185.42379 -2.692 5.660 2011-10-05T04:37:32.437
>
> Priority Changed: Critical
> Modified By: vst
> Modified Date: 2011-10-05 05:00:32
> Priority Changed: Critical
> Modified By: vst
> Modified Date: 2011-10-05 05:00:32
> 2011-10-06 03:36:00 vst
> Add email report sent to INAF/OCAM on the issue. Anisotropy plots are found on vst at odyssey4:smieske_mod/
>
> **************************************************************************************
>
> Steffen Mieske wrote:
>
> Hi Pietro,
>
> tonight we did a number of tests of the rotation pattern, with several sequence that went through the meridian. Below the list of IQ measurements, and the corresponding list of telescope positions. I also attach all corresponding anisotropy plots.
>
> Explanation of what was done, image numbers OMEGACAM_IMG_OBS279_00xx:
>
> Images 1-14: Altitude at meridian 84.8 degrees
> Images 15-19: Altitude at meridian 74.8 degrees
>
> 1: Guiding with telescope, OCAM IA converged immediately before. Strong rotation pattern.
>
> 2&3 Guiding without telescope, with same OCAM IA setup as image 1. Overwhelmingly strong rotation pattern.
>
> 4 useless, aborted due to rotator on limit
>
> 5-9: Guiding with telescope, with OCAM IA converged before first image. We actually converged the IA without the guide probe in, then paused and put the guide probe in, started guiding. Rotation pattern strongest in the first image, then aligned image elongation in 4th and 5th image.
>
> 10-14: Guiding with 2 stars on OmegaCAM, with OCAM IA converged before first image. Consistent rotation pattern in images 3-5, image alignment in image 1, intermediate pattern in image 2.
>
> 15-19: [at 74.7 altitude] Guiding with 2 stars on OmegaCAM, with OCAM IA converged before first image. Very good IQ throughout, only marginal weak rotation pattern visible.
>
> *I would currently conclude to avoid +- 30 min of meridian within ~12 degrees in altitude.*
>
> Cheers,
> Steffen
>
> LIST OF IQ MEASUREMENTS:
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------
> Date OBid Filter | ImaQuality Ellipticity | N_Ell | MeanIQ | IQ_degr | MeanELL | N_reduced
> | Chip65 Chip76 Chip85 Chip96 | | Ima OB/F | Ima OB/F | Ima OB/F | --------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> 2011-10-06T00:23:44.503 607484 i_SDSS 1.10 0.22 0.75 0.05 0.78 0.07 1.12 0.10 1 0.94 1.45 0.11 8
> 2011-10-06T00:28:29.686 607484 i_SDSS 1.18 0.26 1.36 0.25 1.34 0.31 2.35 0.38 6 1.65 1.37 0.26 8
> 2011-10-06T00:33:10.119 607484 i_SDSS 1.35 0.31 1.51 0.33 1.53 0.31 2.11 0.41 7 1.67 1.17 0.32 8
> 2011-10-06T00:37:54.352 607484 i_SDSS 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
> 2011-10-06T00:53:52.031 607484 i_SDSS 0.98 0.18 0.75 0.11 0.60 0.06 0.80 0.09 0 0.78 1.33 0.10 8
> 2011-10-06T00:58:37.013 607484 i_SDSS 0.75 0.08 0.63 0.09 0.57 0.07 0.79 0.05 0 0.69 1.23 0.08 8
> 2011-10-06T01:03:18.377 607484 i_SDSS 0.82 0.09 0.66 0.12 0.69 0.06 0.83 0.03 0 0.74 1.24 0.08 8
> 2011-10-06T01:08:02.450 607484 i_SDSS 0.91 0.14 0.83 0.19 0.73 0.15 0.95 0.10 0 0.86 1.16 0.14 8
> 2011-10-06T01:12:43.082 607484 i_SDSS 2.20 0.59 2.31 0.61 2.22 0.62 2.25 0.58 8 2.24 0.99 0.60 8
> 2011-10-06T01:28:35.792 607484 i_SDSS 0.82 0.19 0.61 0.15 0.60 0.12 0.73 0.13 1 0.68 1.27 0.15 8
> 2011-10-06T01:33:18.595 607484 i_SDSS 0.84 0.04 0.51 0.05 0.54 0.05 0.98 0.11 0 0.71 1.74 0.07 8
> 2011-10-06T01:38:02.767 607484 i_SDSS 1.00 0.17 0.61 0.08 0.64 0.04 1.03 0.09 0 0.82 1.63 0.10 8
> 2011-10-06T01:42:43.200 607484 i_SDSS 1.03 0.21 0.77 0.08 0.71 0.07 0.88 0.09 1 0.83 1.27 0.10 8
> 2011-10-06T01:47:27.343 607484 i_SDSS 0.73 0.11 0.67 0.03 0.67 0.05 0.83 0.09 0 0.74 1.22 0.08 8
> 2011-10-06T02:03:43.633 607484 i_SDSS 0.55 0.04 0.57 0.05 0.60 0.05 0.63 0.04 0 0.59 1.00 0.05 8
> 2011-10-06T02:08:25.935 607484 i_SDSS 0.57 0.05 0.67 0.04 0.68 0.05 0.64 0.04 0 0.64 0.91 0.05 8
> 2011-10-06T02:13:11.328 607484 i_SDSS 0.61 0.07 0.59 0.05 0.61 0.04 0.61 0.04 0 0.60 0.99 0.05 8
> 2011-10-06T02:17:52.141 607484 i_SDSS 0.50 0.03 0.54 0.04 0.56 0.06 0.62 0.06 0 0.54 0.95 0.05 8
> 2011-10-06T02:22:36.144 607484 i_SDSS 0.65 0.05 0.65 0.04 0.67 0.05 0.74 0.04 0 0.67 0.91 1.04 1.22 0.04 0.13 8
>
>
> --------------------------------------------------------------------------------------------------------------------------------------------------------------------
> Date OBid Filter | ImaQuality Ellipticity | N_Ell | MeanIQ | IQ_degr | MeanELL | N_reduced
> | Chip65 Chip76 Chip85 Chip96 | | Ima OB/F | Ima OB/F | Ima OB/F | --------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>
>
> CORRESPONDING LIST OF TELESCOPE POSITIONS:
>
> wocoff astro:/data/raw/2011-10-05 1590 > dfits *OBS279_00*fits | fitsort ADA.ABSROT.START ADA.ABSROT.END TEL.PARANG.START TEL.PARANG.END TEL.AZ TEL.ALT DATE-OBS
> FILE ADA.ABSROT.START ADA.ABSROT.END TEL.PARANG.START TEL.PARANG.END TEL.AZ TEL.ALT DATE-OBS OMEGACAM_IMG_OBS279_0001.fits 164.47242 174.49593 -15.383 -5.347 345.354 84.564 2011-10-06T00:23:44.503
> OMEGACAM_IMG_OBS279_0002.fits 175.71610 186.22770 -4.130 6.425 356.070 84.760 2011-10-06T00:28:29.686
> OMEGACAM_IMG_OBS279_0003.fits 187.45648 197.40237 7.613 17.590 7.273 84.752 2011-10-06T00:33:10.119
> OMEGACAM_IMG_OBS279_0004.fits 198.60563 147.39008 18.788 0.000 17.860 84.445 2011-10-06T00:37:54.352
> OMEGACAM_IMG_OBS279_0005.fits 142.90366 150.39486 -36.994 -29.450 324.928 83.588 2011-10-06T00:53:52.031
> OMEGACAM_IMG_OBS279_0006.fits 151.50894 160.39227 -28.332 -19.461 333.011 84.143 2011-10-06T00:58:37.013
> OMEGACAM_IMG_OBS279_0007.fits 161.60301 171.54466 -18.248 -8.290 342.622 84.551 2011-10-06T01:03:18.377
> OMEGACAM_IMG_OBS279_0008.fits 172.86473 183.40449 -6.968 3.579 353.319 84.774 2011-10-06T01:08:02.450
> OMEGACAM_IMG_OBS279_0009.fits 184.69984 194.84389 4.916 15.015 4.617 84.793 2011-10-06T01:12:43.082
> OMEGACAM_IMG_OBS279_0010.fits 143.79346 151.51175 -36.038 -28.327 325.816 83.668 2011-10-06T01:28:35.792
> OMEGACAM_IMG_OBS279_0011.fits 152.58166 161.58312 -27.254 -18.228 334.089 84.207 2011-10-06T01:33:18.595
> OMEGACAM_IMG_OBS279_0012.fits 162.85029 172.94208 -16.920 -6.856 343.807 84.593 2011-10-06T01:38:02.767
> OMEGACAM_IMG_OBS279_0013.fits 174.23008 184.70970 -5.526 4.955 354.697 84.794 2011-10-06T01:42:43.200
> OMEGACAM_IMG_OBS279_0014.fits 186.08491 196.19874 6.288 16.393 6.011 84.787 2011-10-06T01:47:27.343
> OMEGACAM_IMG_OBS279_0015.fits 170.31934 173.89151 -9.613 -6.040 351.878 74.643 2011-10-06T02:03:43.633
> OMEGACAM_IMG_OBS279_0016.fits 174.35183 177.97861 -5.579 -1.966 355.278 74.763 2011-10-06T02:08:25.935
> OMEGACAM_IMG_OBS279_0017.fits 178.48581 182.11053 -1.444 2.181 358.770 74.819 2011-10-06T02:13:11.328
> OMEGACAM_IMG_OBS279_0018.fits 182.55949 186.16824 2.616 6.225 2.214 74.810 2011-10-06T02:17:52.141
> OMEGACAM_IMG_OBS279_0019.fits 186.59925 190.20773 6.656 10.279 5.625 74.737 2011-10-06T02:22:36.144
> wocoff astro:/data/raw/2011-10-05 1591 >
>
>
> *******************************
>
>
> Pietro Schipani wrote:
>
> Hola Steffen,
>
> unfortunately I do not think this is the problem [refering to rotator running on 4 encoders]: now we are working with 1 encoder (I have just checked with Laurent), we had archived the correct version. Laurent did a test just a few minutes ago in the same conditions (meridian, small zenith angle) and the rms error was about 0.15-0.2 arcsec, very small for the rotator. After refilling of LN2 he will try again.
>
> - If the problem is in the control loop, we should see a dramatic increase of the tracking error in the panel (what we are trying to reproduce with Laurent at day-time), something like error = 50-100 arcsec. We should try to save error data associated with bad images, but even a visual inspection may be sufficient for the moment.
> - If there is a problem in the quality of feedback (i.e. what the encoder says is not totally true), we should likely see the effect on any image (at meridian, and not). This does not seem to be the case.
> - If the problem is related to the amplitude of rotator movement during the image, we should see the effect also on images far from meridian, with the same rot excursion (5-7 degree). This might in theory happen in case of slightly wrong gear ratio, that we had excluded in the past and would strongly affect the pointing. So far I did not have this feeling from your plots, and as far as I know the pointing for rotator angles now is working fine.
>
> As usual we should try to know the enemy, to understand how we can defeat it... we need more information.
>
> Ciao,
> Pietro
>
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