MODS1 and MODS2 rotator centers (during cloudy LUCI-AO night)

MODS1 and MODS2 were mounted on 2017 October 21 and 20, respectively, but MODS2 required realignment of the laser launch block and the red grating turret sensors before it could be used on-sky. So while the initial checkout, which included measurement of rotator centers on both blue and red channel cameras, was done on October 30 for MODS1, it was only done tonight for MODS2. MODS1 was used also and the rotator centers measured tonight are consistent with the results from Com20171030, which were, for MODS1B (1539.5,1541) and for MODS1R (1537.0,1547.1).

Image filenames are all: modsNc.20171129.000n.fits where N=1,2, c=b,r and n = 3,4,5,6. Each of these images is a track mode preset at the given position angle.

A version of modsrc (LBTtools.LBC.modsrc) which uses only the source extractor detections within the 3K x 3K field, excluding a 100-pixel buffer zone around the edges. The x,y coordinates of the detected sources for a pair of images were matched with IRAF.immatch.xyxymatch and then geomap was used to determine the mapping between the two images, using only the most basic fit=rotate and order 2 (not much difference for a fit with more free parameters). The fit rms was ~0.6-1.5 pixels. The output of geomap: xshift, yshift, rotation was used to determine the rotator center (xrc,yrc) as follows:
xrc = (a + c*ycor)/(1-b)
yrc = -1*(a*e + d*(1-b))/(c*e - (1-f)*(1-b))

where
   gcos = cos(grot/d2r)
   gsin = sin(grot/d2r)
   b = cos(rotation)
   c = sin(rotation)
   e = -sin(rotation)
   f = cos(rotation)
   a = xshift
   d = yshift

preset posangle mods2b mods2r mods1b mods1r
track 0 3 3 3 3
track 180 4 4 4 4
track 270 5 5 5 5
track 90 6 6 6 6

approx avg 180 1513 1511 1506 1535 1537 1538 1536 1545
Rotator Centers
    M2B M2R M1B M1R
pair dtheta xrc yrc xrc yrc xrc yrc xrc yrc
3 & 4 180 1512.34 1512.05 1506.6 1537.1 1536.4 1537.09 1534.6 1544.9
5 & 6 180 1513.02 1509.86 1506 1532 1538.4 1538.4 1537.0 1545.1
4 & 6 90 1517.25 1508.40 1511 1533.8 1542.4 1540.5 1540.4 1549.9
3 & 6 90 1508.7 1507.12 1503.0 1532.5 1539.5 1531.2 1539.6 1539.1
3 & 5 90 1510.07 1514.12 1506.7 1534.4 1531.3 1537.4 1531.0 1542.6
4 & 5 90 1514.28 1514.30 1503.7 1536.8 1536.6 1542.2 1532.3 1548.5
avg all 1512.6 1511.0 1506.2 1534.4 1537.4 1537.8 1535.8 1545.0
sig(n-1) pix 3.0 3.0 2.8 2.1 3.7 3.8 3.8 3.9
sig(n-1) arcsec 0.36 0.36 0.34 0.26 0.44 0.45 0.47 0.48

-- %USERSIG{OlgaKuhn - 2017-11-30}%

Comments

 
Topic revision: r3 - 20 Aug 2018, OlgaKuhn
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding Foswiki? Send feedback