Request for linearized WCS in .ch.fits images to have CRPIX[12] in center of chip rather than FPA

[Michael Wood-Vasey]

The linearized WCS written to the .ch.fits files in the 200901 data release uses the center of the FPA as the reference for the linear WCS. This leads extrapolation errors near the edge of the FPA. I suggest that the linear solution use the center of each chip. I believe this would significantly improve the quality of the linearized WCS solution.

I looked through 'magic/remove/src/streaksastrom.c', 'psLib/src/astro/psCoord.c', and 'psModules/src/astrom/pmAstrometryWCS.c', and read through the notes at the end of 'streakastrom.c' but couldn't quite trace through what should be changed.

Example of CRPIX1, CRPIX2. The CRVAL1, CRVAL2 are the same for each image: 35.8749731512529 -4.25000889796096.

[wwoodvas@iliadaccess03 MD01_20081002_1]$ gethead CRPIX1 CRPIX2 36475/chip/*[0-9].ch.fits
o4741g0234o.36475.ch.11948.XY01.ch.fits -15004.7837922089 -10418.4040333303
o4741g0234o.36475.ch.11948.XY02.ch.fits -15000.9896760033 -5290.12598817358
o4741g0234o.36475.ch.11948.XY03.ch.fits -15016.1747549677 -74.3838630063315
o4741g0234o.36475.ch.11948.XY04.ch.fits -15001.6079393223 5044.39263953862
o4741g0234o.36475.ch.11948.XY05.ch.fits -15010.8859640919 10186.9451977694
o4741g0234o.36475.ch.11948.XY06.ch.fits -15012.6921363265 15341.6585583353
o4741g0234o.36475.ch.11948.XY10.ch.fits -10041.5404914163 -15532.0353241814
o4741g0234o.36475.ch.11948.XY11.ch.fits -10028.5427592865 -10432.1992066181
o4741g0234o.36475.ch.11948.XY12.ch.fits -10022.8451218727 -5292.00262132451
o4741g0234o.36475.ch.11948.XY13.ch.fits -10043.7165582872 -142.584418283285
o4741g0234o.36475.ch.11948.XY14.ch.fits -10041.7096958073 5013.34390868683
o4741g0234o.36475.ch.11948.XY15.ch.fits -10059.779584053 10175.3029823195
o4741g0234o.36475.ch.11948.XY16.ch.fits -10089.9126445275 15320.0186777458
o4741g0234o.36475.ch.11948.XY17.ch.fits 69569.6806217463 36197.2648429808
o4741g0234o.36475.ch.11948.XY20.ch.fits -5077.15160630519 -15558.428746925
o4741g0234o.36475.ch.11948.XY21.ch.fits -5089.1292514725 -10393.1676791935
o4741g0234o.36475.ch.11948.XY22.ch.fits -5075.11800369091 -5260.26385270211
o4741g0234o.36475.ch.11948.XY23.ch.fits -5074.31020638533 -97.5946782684938
o4741g0234o.36475.ch.11948.XY24.ch.fits -5069.37580530681 5047.81783751341
o4741g0234o.36475.ch.11948.XY25.ch.fits -5076.05922695554 10190.9773601644
o4741g0234o.36475.ch.11948.XY26.ch.fits -5073.1045875733 15336.7466833954
o4741g0234o.36475.ch.11948.XY27.ch.fits -5088.13546969399 20478.30651256
o4741g0234o.36475.ch.11948.XY30.ch.fits -51.0667401204102 -15546.2346285717
o4741g0234o.36475.ch.11948.XY31.ch.fits -90.563596826204 -10413.7081851949
o4741g0234o.36475.ch.11948.XY32.ch.fits -92.2688792876398 -5252.17731153943
o4741g0234o.36475.ch.11948.XY33.ch.fits -97.6726138915179 -97.7760148992492
o4741g0234o.36475.ch.11948.XY34.ch.fits -91.2626791021934 5037.12548072602
o4741g0234o.36475.ch.11948.XY35.ch.fits -93.5617064752887 10186.270142933
o4741g0234o.36475.ch.11948.XY36.ch.fits -78.202511819518 15351.1661164999
o4741g0234o.36475.ch.11948.XY37.ch.fits -102.564259657763 20492.702872569
o4741g0234o.36475.ch.11948.XY40.ch.fits -23.3714907117367 20403.7983650403
o4741g0234o.36475.ch.11948.XY41.ch.fits -30.9545943132476 15262.9212869079
o4741g0234o.36475.ch.11948.XY42.ch.fits -16.4347557547518 10125.0565809475
o4741g0234o.36475.ch.11948.XY43.ch.fits -27.6692277242369 4968.3227935852
o4741g0234o.36475.ch.11948.XY44.ch.fits -25.4790735424882 -180.603291110531
o4741g0234o.36475.ch.11948.XY45.ch.fits -40.6868869460475 -5322.21257043545
o4741g0234o.36475.ch.11948.XY46.ch.fits -28.9575823299045 -10486.5467418967
o4741g0234o.36475.ch.11948.XY47.ch.fits -24.3605869006741 -15613.2271132766
o4741g0234o.36475.ch.11948.XY50.ch.fits -4978.86207714216 20417.0437163425
o4741g0234o.36475.ch.11948.XY51.ch.fits -5014.00984915671 15264.6285098334
o4741g0234o.36475.ch.11948.XY52.ch.fits -4996.53516631847 10125.4897860093
o4741g0234o.36475.ch.11948.XY53.ch.fits -4999.63497982995 4962.90503433352
o4741g0234o.36475.ch.11948.XY54.ch.fits -4997.35247968921 -181.767683814719
o4741g0234o.36475.ch.11948.XY55.ch.fits -5001.71386385374 -5339.00232815702
o4741g0234o.36475.ch.11948.XY56.ch.fits -5017.59378561791 -10475.3324223995
o4741g0234o.36475.ch.11948.XY57.ch.fits -5022.46632934941 -15620.2629456785
o4741g0234o.36475.ch.11948.XY60.ch.fits -9987.43552233357 20398.0621243
o4741g0234o.36475.ch.11948.XY61.ch.fits -9988.42970835103 15270.9865308615
o4741g0234o.36475.ch.11948.XY62.ch.fits -9972.08835274121 10142.4433172826
o4741g0234o.36475.ch.11948.XY63.ch.fits -9980.13442110098 4958.01202847471
o4741g0234o.36475.ch.11948.XY64.ch.fits -9974.97223958305 -205.88119037875
o4741g0234o.36475.ch.11948.XY65.ch.fits -9996.10695529205 -5327.32145408791
o4741g0234o.36475.ch.11948.XY66.ch.fits -10001.8389058899 -10468.7729156031
o4741g0234o.36475.ch.11948.XY67.ch.fits -9977.9332645378 -15633.9093896935
o4741g0234o.36475.ch.11948.XY71.ch.fits -14927.7025414871 15248.8913393407
o4741g0234o.36475.ch.11948.XY72.ch.fits -14948.9184546813 10119.5642841248
o4741g0234o.36475.ch.11948.XY73.ch.fits -14940.4852931566 4979.25994573107
o4741g0234o.36475.ch.11948.XY74.ch.fits -14944.1694266201 -180.612074393042
o4741g0234o.36475.ch.11948.XY75.ch.fits -14951.9664061967 -5320.0081595705
o4741g0234o.36475.ch.11948.XY76.ch.fits -14949.23833074 -10472.6088945878

[eugene]

I believe this bug is addressed now by the fixes to the astrometry implemented in r27461

[bills]

Fix integrated Wed May 5 13:36:06 HST 2010