Summary of LBC IQ 22,23,24 June 2013

This page was created to collect plots made from the 3 nights devoted to studying LBC IQ issues: 2013 June 22,23,24 UT and to discuss these.

Data for LBC Collimation Models

Background: The LBC Collimation Models that are in use were determined from months of archival data (2010 December to 2011 June, in /data/RB_CollTables_link/ and /d1/kuhn/RBCollTables/). These use the mirror positions (PSF total collimation) recorded in the headers of the last extra-focal pupil images before dofpia exits. A 0.8 mm offset was added to the mirror Z position (since these were extra-focal pupils), and the X,Y,RX,RY positions were range-balanced, offline, to predict a new set of X,Y,Z,RX,RY positions as a function of T301 and elevation. No copointing could be done. I think Andrew incorporated the copointing, offline, later?
  • Script to do the offline range-balancing is on ohia in ~/iraf/Mytools/oflrangebal.cl

Although the last extra-focal pupil images are, by intention, spherically aberrated, the final Z4 exit correction that accompanies the Z11 exit correction sent to remove the aberration is typically small enough that it should not significantly effect the trend of Z with elevation and temperature. Indeed, from the FPIA logs, we see Z4(exit) is typically ~1000 nm (which corresponds to delt_Z~0.0379 mm). Z4(exit) is computed within DOFPIA as a function only of seeing, so it cannot have much range (Z4(exit)~500-1400 nm or 0.02-0.05mm delt_Z for estimated seeing 0.6"-2").

Z4(exit) = -1.75*Z11(exit) = -1.75 * (FinalZ11zero + FinalZ11scale*seeing), where
Channel FinalZ11Zero FinalZ11scale
Blue -100 -350
Red -75 -350

To check how well the collimation model was doing, for all object observations made during several nights in the spring of 2013, I plotted the mirror Z position against elevation. For objects observed through transit, the track of mirror Z position along which the object rose did not overlap with the track along which the object set. (Attach example plot). Is this due to hysteresis or uncorrected thermal effects?

To address this question, on two nights (23 and 24 June), we obtained data for co-pointed and range balance collimation models. Our procedure was to:
  1. at the start of the night, as usual, clear active optics. Active optics was not cleared during collection of data.
  2. Slew to a target with well-known coordinates. USNO-B1.0 stars were used for these targets.
  3. Run dofpia to focus and collimate
  4. Obtain a pair of 1-sec images of this USNO-B1.0 star.
  5. Run lbcrangebal
  6. Obtain a pair of 1-sec images of this USNO-B1.0 star again.
  7. Repeat 2-6.
The temperature used by the collimation model is T301, the steel temperature at the upper C-ring extension. The range in T301 over the time the data were collected was:
date T301 (deg C)
20130623 12.5 - 9
20130624 11.8 - 9.4

On 23 June:
  • elevation sequence made almost 2 cycles down up and the tracks were (datafiles plotted use the names below: "down 1", "up 1", "down 2", ...):
    • down 1: 85, 75, 65, 60, 55, 50, 45, 35, 25, 15 (dofpia stopped, no data), 20, 15
    • up 1: 15(obs not repeated), 25, 35, 45, 50, 55, 60, 65, 75, 85
    • down 2: 85(obs not repeated), 75, 65, 60, 55, 50, 45, 35, 25, 15
    • up 2: 15(obs not repeated), 20, 30, 40 (twilight)
On 24 June, the elevation sequence repeated that for 23 June, but made only one cycle down and up.
    • down 1: 83, 78, 67, 60, 55, 50, 45, 35, 25, 15
    • up 1: 15 (obs not repeated), 25, 35, 45, 50, 55, 60, 65, 75 (had to close for wind after this).
    • reopened, cleared active optics, and focussed and collimated at 77 deg
      • use the Z data point corrected by 0.8mm on plots (black). *This point falls closer to the original downward track when the T301 term is removed (see sx_lut_20130624.jpg and dx_lut_20130624.jpg).

Dofpia: On both nights, dofpia took many more iterations at low elevation (poor seeing) than at high elevations, and during each of these iterations, it added Z11, Z22 and removed Z4. Is it driven by the fitting of the outer diameter (Z4) or by the ratio Din/Dout (Z11)? We think Z11, and the need to reach the condition that the ratio: Din/Dout = 0.2(blue) or 0.26(red). (Noting here that Din/Dout should be 0.16/0.2 for an unaberrated pupil, but slightly larger for the spherically aberrated pupil to which dofpia converges - and then exits with Z11/Z4 to return to the unaberrated image.) FPIA logs for all three nights are attached: Red/Blue2013-06-22/23/24.Log

The mirror positions along each elevation track are plotted against elevation for SX and DX and 20130623 and 20130624. There are 8 plots total (all in /data/HubMoves).
  • sx_lut_20130623.jpg, dx_lut_20130623.jpg, sx_lut_20130624.jpg and dx_lut_20130624.jpg:
    • X,Y,Z,RX,RY as read from the header, i.e. with the T301 correction made by PSF included. The collimation models are plotted for the temperature range, T301 = 9 (blue), 10.75 (black) and 12.5 (red).
  • sx_lut0_20130623.jpg, dx_lut0_20130623.jpg, sx_lut0_20130624.jpg and dx_lut0_20130624.jpg:
    • X,Y,Z,RX,RY from the header and with the T301 correction subtracted. The collimation models are plotted for T301=0.
  • On all of these the filter focus offset, -0.02 mm for V-BESSEL on LBC-Blue(SX) and +0.069 for V-BESSEL on LBC-Red(DX) is subtracted from the header value (this would be necessary to combine data taken through different filters, but for these nights on which the data are taken through the same filter, it is a constant offset for every datapoint).
  • The mirror positions in the header are the total collimation positions which are the sum:
    • Total = Global_offset + Lookup_Table(elev) + Temp_Corr(T301) + Instrument_Offset + Active_Optics + (Manual_Pointing + Pointing)
      • Lookup_Table is a function of elevation only
      • Temp_Corr is a function of T301
      • Instrument_Offset.
        • for Z, this is filter focus offset
        • for X,Y,RX,RY this holds the cumulative corrections sent by lbcrangebal.
    • So for lut0:
        • Z = Z(hdr) - Tcoeff*T301 - filter_focus_offset
        • X = X(hdr), Y=Y(hdr), RX = RX(hdr) and RY=RY(hdr)
    • And for lut0:
        • Z = Z(hdr) - filter_focus_offset.
        • X = X(hdr), Y=Y(hdr), RX = RX(hdr) and RY=RY(hdr)
Some observations from the plots:
  • The tracks down,up,down do not overlie one another. This is in Z as well as in Y/RX and X/RY and for both SX and DX.
    • High elevation points are separated by delta_Z = 0.35mm, low elevation ones by delta_Z = 0.2 mm. These are with the T301 correction removed. With it, the spread is larger. The spread is similar for both SX and SX.
    • Since the data are co-pointed, trends in Y/RX and X/RY are expected to be coupled for SX and DX.
    • delta_Z = -0.35 mm, the spread in Z at high elevation, corresponds to diff(Z4)~ -9200 nm and delta_Z = -0.2 mm, the spread in Z at low elevation, corresponds to diff(Z4) ~ -5300nm
      • There is a Z4/Z11/Z22 matrix which dofpia uses to account for crosstalk between the application of these Zernike aberrations to M1. So if you apply 1000 nm Z11, you would measure not only the Z11 applied but also Z4 and Z22. If we assume the Z4/Z11 and Z4/Z22 gains used by dofpia, -1.75 and -8: Z4 = -1.75 * Z11 + -8 * Z22. ...
    • Plots of Zernikes Z4, Z5,6 Z7,8 Z11 and Z22 following these down/up/down/up tracks are attached.
        • between the 1st and 2nd high-elev point:
          • Z11 decreased by 100 nm for DX, about same for SX.
          • Z22 decreased by -250 for both.
          • Z4 decreased by ~ 6000 nm (SX), ~7000 nm (DX).
        • between the 1st and 2nd low-elev point:
          • Z11 increased by ~ 1000 nm for DX, ~500 for SX
          • Z22 decreased slightly, but by ~<100 nm, for both.
          • Z4 decreased by 4800 nm (SX) and 7000 (DX)
    • The track in mirror Z position is reflected, at least partly, by the total Z4.
    • The changes in Z11 and Z22 are smaller than what is expected based on the Z4/Z11/Z22 gains and the change in Z4... other factors involved...
    • Note that the Z4/Z11/Z22 FPIA gains are not the same as those used for M1 by the Gregorian active optics.

Best-focus

During 23 June 2013, we obtained through-focus sequences at 3 different elevations, both along the first downward track and along the first upward track. We obtained these at PA=0 and PA=180 (see Focal Plane Tilt, below).

These focus sequences were analyzed with IRAF.obsutil.starfocus to fit the FWHM vs focus data for a number of stars within the central 5 arcmin x 5 arcmin about the rotator center. The results are in the tables below and plots attached.

Analysis procedure was to:
  • create simple FITS file of LBCCHIP2 image only:
    • imcopy lbcb.20130623.hhmmss.fits[2] lfcb.20130623.hhmmss.fits
      • SExtractor runs on MEF or simple FITS, but how can I tell it to run only on extension 2 of a MEF? So I created a simple FITS file.
  • run skybox, a hacked version of skyseeing (itself hacked from allseeing), which is in my LBTtools on ohia. It works on a simple FITS file. It is run on the middle image of the focus sequence (the one supposedly at best focus) to create a catalog of stars in ./Misc. The program uses SExtractor to create the catalog. The output catalog is given a name like Bhhmmss.cat.
  • run readcat.pl (in /data/20130623/Misc) to read this catalog, select stars within a 5' x 5' box around the rotator center (average rotcen for both Blue/Red taken to be 1056, 2918, so region is [390:1723, 2252:3585] and output a image_cursor file, Bhhmmss_starfoc5.cat, in the format used by starfocus.Catalog files stored in subdir under /data/20130623/Misc.
  • run starfocus
    • starfoc @bfoc0a.list focus=focusoff rad=7 sbin=5 swid=5 iter=2 logfile="bfoc0a.log" imagecur="Misc/Bhhmmss_starfoc5.cat"
    • delete stars, starting with those having very high ellipticities or fwhm. For some I deleted a focus point if it looked like it was systematically high (seeing blew up?) and compared the result with and without this point. Though at 25 deg, the seeing did vary (the best-fwhm varied) from ~0.95-1.35", the
    • log files are sometimes named with hhmmss.
  • data files (tables below from these) contain best-focus from starfoc, FWHM corresponding to best-focus, sequence name, filename of middle image of sequence and OB name (truncated, so RB_rV_superfoc7_pa should end with pa180). estseeing is seeing estimated by FPIA on the last pupil image obtained before dofpia exited.

Blue: /data/20130623/bestfoc_1k_x_1k.dat

bestfoc bestfwhm seq filename dd dm ds uty utm utd hh mm ss lbcobnam estseeing
-0.016 2.74 bfoc0a lfcb.20130623.042659.fits +74 53 02.91 2013 06 23 04 26 59.451 RB_rV_superfoc7 1.32
-0.033 3.10 bfoc180a lfcb.20130623.043357.fits +74 41 15.69 2013 06 23 04 33 57.512 RB_rV_superfoc7_pa 1.32
+0.022 3.02 bfoc0b lfcb.20130623.051208.fits +55 13 17.69 2013 06 23 05 12 08.036 RB_rV_superfoc7 1.05
+0.0017 3.20 bfoc180b lfcb.20130623.051902.fits +55 09 50.86 2013 06 23 05 19 02.616 RB_rV_superfoc7_pa 1.05
+0.032 4.52 bfoc0c lfcb.20130623.061507.fits +25 47 06.75 2013 06 23 06 15 07.682 RB_rV_superfoc7 1.23
+0.07 5.64 bfoc180c lfcb.20130623.062204.fits +25 47 55.64 2013 06 23 06 22 04.642 RB_rV_superfoc7_pa 1.23
+0.086 5.21 bfoc0d lfcb.20130623.071804.fits +24 57 42.91 2013 06 23 07 18 04.562 RB_rV_superfoc7 1.23
+0.138 5.42 bfoc180d lfcb.20130623.072457.fits +24 58 42.76 2013 06 23 07 24 57.236 RB_rV_superfoc7_pa 1.23
+0.008 3.45 bfoc0e lfcb.20130623.080835.fits +55 08 32.43 2013 06 23 08 08 35.276 RB_rV_superfoc7 0.95
-0.003 2.85 bfoc180e lfcb.20130623.081529.fits +55 05 17.58 2013 06 23 08 15 29.133 RB_rV_superfoc7_pa 0.95
+0.0110 2.75 bfoc0f lfcb.20130623.084848.fits +75 03 13.75 2013 06 23 08 48 48.104 RB_rV_superfoc7 0.85
+0.016 2.73 bfoc180f lfcb.20130623.085539.fits +74 52 06.29 2013 06 23 08 55 39.805 RB_rV_superfoc7_pa 0.85

Red: /data/20130623/rbestfoc_1k_x_1k.dat

bestfoc bestfwhm seq filename dd dm ds uty utm utd hh mm ss lbcobnam estseeing
0.022 2.83 rfoc0a lfcr.20130623.042625.fits +74 53 32.43 2013 06 23 04 26 25.588 RB_rV_superfoc7 0.94
0.011 2.74 rfoc180a lfcr.20130623.043327.fits +74 41 55.49 2013 06 23 04 33 27.416 RB_rV_superfoc7_pa 0.94
0.025 2.90 rfoc0b lfcr.20130623.051138.fits +55 13 25.25 2013 06 23 05 11 38.151 RB_rV_superfoc7 0.68
0.0259 3.02 rfoc180b lfcr.20130623.051833.fits +55 10 02.35 2013 06 23 05 18 33.463 RB_rV_superfoc7_pa 0.68
0.046 4.26 rfoc0c lfcr.20130623.061442.fits +25 47 05.30 2013 06 23 06 14 42.463 RB_rV_superfoc7 1.05
0.057 5.94 rfoc180c lfcr.20130623.062134.fits +25 47 52.57 2013 06 23 06 21 34.041 RB_rV_superfoc7_pa 1.05
0.092 4.62 rfoc0d lfcr.20130623.071735.fits +24 57 40.86 2013 06 23 07 17 35.744 RB_rV_superfoc7 1.18
0.095 5.64 rfoc180d lfcr.20130623.072425.fits +24 58 39.01 2013 06 23 07 24 25.635 RB_rV_superfoc7_pa 1.18
0.03 3.78 rfoc0e lfcr.20130623.080806.fits +55 08 39.54 2013 06 23 08 08 06.229 RB_rV_superfoc7 0.65
0.026 3.33 rfoc180e lfcr.20130623.081455.fits +55 05 32.80 2013 06 23 08 14 55.213 RB_rV_superfoc7_pa 0.65
0.051 3.0 rfoc0f lfcr.20130623.084819.fits +75 03 36.81 2013 06 23 08 48 19.760 RB_rV_superfoc7 0.56
0.062 2.88 rfoc180f lfcr.20130623.085507.fits +74 52 51.74 2013 06 23 08 55 07.588 RB_rV_superfoc7_pa 0.56

The best-focus determined from starfocus is seen to depend on seeing or elevation. I concentrated first on plots of best-focus against seeing, given the behavior of dofpia at poor seeing (note: look through FPIA logs. Does dofpia always do this, at any elevation, for est-seeing >~1.5"?)

Attached jpgs, bestfocus_vs_seeing.jpg and bestfoc_vs_seeing_zoom.jpg, plot the seeing (bestfwhm converted to arcsec) on the X-axis and the best-focus (mm), FPIA-estimated seeing (arcsec) and elevation on the Y-axis.
    • Thick red line connects points, (best-focus,seeing)
    • Light magenta line is linear fit to these data (best-focus,seeing)
    • green line connects points, (estseeing,seeing)
    • Thick green line is estseeing=seeing
    • cyan line is linear fit to (estseeing,seeing)
    • Blue points mark elevation vs seeing.

Linear least squares fits to the data of: best-foc[mm] = seeing[arcsec] * a + b and est-seeing = seeing[arcsec]* c + d yield:
chan a b c d filter focus offset filter
blue 0.16 -0.11 0.35 0.81 -0.02 V-BESSEL according to fit, filter focus offset of -0.02 mm corresponds to seeing 0.56", 0.05 mm for 1"
red 0.075 -0.018 0.66 0.28 0.036 r-SLOAN according to fit, 0.7" seeing -> 0.036 mm

Notes from plots:
  • Both the best-focus and estimated seeing have a stronger dependence on seeing for blue than for red channel.
  • The best-focus determined from starfoc does have a lot of scatter at poor seeing. Could the fit be affected by seeing variations during the 5-min superfoc sequence?
    • The 7-point curves, with delta_focus = 0.06mm, pretty well described a parabola or "V". There were one or two focus points which lay above the curve and I deleted these in star-foc when it seemed warranted.
    • The second 75 deg field (b/rfoc0/180f.list) had many stars, a huge and unreasonable, range of FWHM and ellipticities measured by starfoc. I need to figure out what starfoc was doing here.
  • This type of plot: best-focus vs seeing;
    • illustrates the scatter in the measurements of filter-focus offset, that it is larger for Blue than for Red.
    • That there is a trend in best-focus with seeing may be explained by the behavior of dofpia in poor seeing conditions.
      • There may be also elevation and temperature dependences.

Does adding the offset between best-focus and nominal filter focus offset explain the difference between in the down/up tracks? No. This offset is very small (0.1 mm max) compared to the difference ~0.2 - 0.5 mm between the down/up Z vs elevation tracks.

Focal Plane Tilt

Procedures and Programs:
  • Created IRAF program "startilt" (again modified from others, namely allseeing and iqplot) to:
    • read a list of images taken in a superfocus sequence
      • find the one nominally at 'best-focus' (the focus offsets for V-BESSEL and r-SLOAN are hardwired into the program)
    • create simple fits files, one per extenstion, from this best-focus MEF LBC image
    • run SExtractor on each simple fits file.
    • read the catalog file output by SExtractor, select stars meeting certain criteria, and write out a list of x y coordinates for these stars.
    • create a script (SF.cl) to input to starfocus
      • starfocus is picky --- it sometimes crashes when it comes upon an 'invalid flux profile'. Therefore it is not run within "startilt"
    • cl < SF.cl to run starfocus on each image extension and create a logfile.
  • Use perl script, "fptilt.pl" (currently only on my laptop: /home/olga/Programs/lbcIQ/IQProgs) to parse the log output of starfocus and return best-focus, fwhm, ellipticity referenced to the detector coordinates using the header CRPIX1,CRPIX2 values. Where x,y are coordinates in the focal plane and xc,yc are detector coordinates:
    • for chips 1-3, x = xc - CRPIX1(chip) and y = yc - CRPIX2(chip)
    • for chip 4, x = -yc + CRPIX2(chip4) and y = xc - CRPIX1(chip4)
    • and CRPIX1, CRPIX2 are, for the 4 chips:
chip LBC-Blue LBC-Red
chip CRPIX1 CRPIX2 CRPIX1 CRPIX2
1 -1087 2924 -1044 2913
2 1035 2924 1078 2913
3 3157 2924 3200 2913
4 -1709 2271 -1719 2239

Pupil images (LBC and MODS)

Skirt:

Orientation of LBC extra-focal pupil:
  • Pupil Orientation
    • "Diving" board attached to outer rim of mirror cell near MV hoses, so, nearly 180 deg from the instrument platform, but a little closer to the base of the swing arm than to the 'back', near the gallery. The board can be seen in the extra/intra-focal pupil images attached.

-- OlgaKuhn - 28 Jun 2013

I Attachment Action Size Date Who Comment
bestfoc_vs_seeing_zoom.jpgjpg bestfoc_vs_seeing_zoom.jpg manage 80 K 28 Jun 2013 - 21:56 OlgaKuhn best-focus vs seeing (zoom)
bestfocus_vs_seeing.jpgjpg bestfocus_vs_seeing.jpg manage 91 K 28 Jun 2013 - 21:56 OlgaKuhn best-focus and est-seeing vs seeing
blue2013-06-22.LogLog blue2013-06-22.Log manage 8 K 28 Jun 2013 - 23:07 OlgaKuhn  
blue2013-06-23.LogLog blue2013-06-23.Log manage 21 K 28 Jun 2013 - 23:05 OlgaKuhn  
blue2013-06-24.LogLog blue2013-06-24.Log manage 13 K 28 Jun 2013 - 23:06 OlgaKuhn  
dx_lut0_20130623.jpgjpg dx_lut0_20130623.jpg manage 156 K 28 Jun 2013 - 20:24 OlgaKuhn DX: X,Y,Z,RX,RY vs elev for 20130623 with T301 scaling removed
dx_lut0_20130624.jpgjpg dx_lut0_20130624.jpg manage 143 K 28 Jun 2013 - 20:30 OlgaKuhn DX: X,Y,Z,RX,RY vs elev for 20130624 with T301 scaling removed
dx_lut_20130623.jpgjpg dx_lut_20130623.jpg manage 180 K 28 Jun 2013 - 20:23 OlgaKuhn DX: X,Y,Z,RX,RY vs elev for 20130623
dx_lut_20130624.jpgjpg dx_lut_20130624.jpg manage 159 K 28 Jun 2013 - 20:29 OlgaKuhn DX: X,Y,Z,RX,RY vs elev for 20130624
dxzern20130623.pngpng dxzern20130623.png manage 176 K 29 Jun 2013 - 01:27 OlgaKuhn DX: Z4,Z5,Z6,Z7,Z8,Z11,Z22 vs elev for down/up/down/up tracks
red2013-06-22.LogLog red2013-06-22.Log manage 8 K 28 Jun 2013 - 23:07 OlgaKuhn  
red2013-06-23.LogLog red2013-06-23.Log manage 21 K 28 Jun 2013 - 23:05 OlgaKuhn  
red2013-06-24.LogLog red2013-06-24.Log manage 13 K 28 Jun 2013 - 23:06 OlgaKuhn  
sx_lut0_20130623.jpgjpg sx_lut0_20130623.jpg manage 152 K 28 Jun 2013 - 20:24 OlgaKuhn SX: X,Y,Z,RX,RY vs elev for 20130623 with T301 scaling removed
sx_lut0_20130624.jpgjpg sx_lut0_20130624.jpg manage 133 K 28 Jun 2013 - 20:29 OlgaKuhn SX: X,Y,Z,RX,RY vs elev for 20130624 with T301 scaling removed
sx_lut_20130623.jpgjpg sx_lut_20130623.jpg manage 172 K 28 Jun 2013 - 20:22 OlgaKuhn SX: X,Y,Z,RX,RY vs elev for 20130623
sx_lut_20130624.jpgjpg sx_lut_20130624.jpg manage 149 K 28 Jun 2013 - 20:28 OlgaKuhn SX: X,Y,Z,RX,RY vs elev for 20130624
sxzern20130623.pngpng sxzern20130623.png manage 175 K 29 Jun 2013 - 01:27 OlgaKuhn SX: Z4,Z5,Z6,Z7,Z8,Z11,Z22 vs elev for down/up/down/up tracks
Topic revision: r13 - 01 Sep 2015, OlgaKuhn
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