immatch

Example 1.
Match Image Stars with HST GSC

IMAGE
Click on image for larger version 		This sample image contains world coordinate system fit by imwcs in Example 1. The following header keywords define the WCS: 
EQUINOX =                 2000
CTYPE1  = 'RA---TAN'
CRVAL1  =              243.987
CRPIX1  =                  512
CDELT1  =         -0.000179207
CROTA1  =           -0.0727298
CTYPE2  = 'DEC--TAN'
CRVAL2  =              31.4185
CRPIX2  =                  512
CDELT2  =          0.000179207
CROTA2  =                    0
IMWCS   = 'IMWCS 1.0, 28 June 1996, Doug Mink SAO'

To list the HST Guide Stars in the image, the threshold for a pixel to be checked out as a possible star was set to 5000, and the program was run. 

$ immatch -c gsc -i 5000 testx90mwg.fits
giving the results 
# Arcsec/Pixel: -0.645145 0.645145  Rotation: -0.072730 degrees
# Optical axis: 16:15:56.880  +31:25:06.60 J2000 at (512.00,512.00)
# Optical axis: 16:13:59.776  +31:32:29.78 B1950 at (512.00,512.00)
# 12 matches between gsc and testx90mwg.fits:
 2580.1629 16:15:55.896 +31:19:58.40 13.91  528.5   33.5  -2.15   0.50   1.65
 2580.1878 16:16:10.956 +31:21:42.41 14.92  229.8  196.1  -2.11  -0.12   1.54
 2580.1909 16:15:37.282 +31:23:51.97 14.76  899.7  396.1  -0.99  -0.10   0.73
 2580.1798 16:15:34.867 +31:24:43.45 14.16  947.9  475.8  -0.78  -0.03   0.57
 2580.1485 16:15:52.958 +31:25:15.56 14.88  588.8  526.6  -0.87  -0.51   0.81
 2580.2291 16:16:08.345 +31:26:15.76 13.81  283.5  620.5  -1.06  -0.63   0.99
 2580.1943 16:15:41.477 +31:26:37.54 14.84  817.0  653.4  -0.60  -0.46   0.64
 2580.1696 16:15:49.339 +31:26:42.40 13.38  661.3  661.0  -0.44  -0.45   0.55
 2580.1207 16:15:45.511 +31:27:48.64 13.50  737.1  763.5  -0.61  -0.35   0.56
 2580.1158 16:16:12.139 +31:28:54.01 13.99  209.4  861.3  -0.41   2.37   2.39
 2580.2147 16:16:21.072 +31:29:28.82 14.47   30.2  921.7  -2.36  -1.57   2.32
 2580.1403 16:15:34.330 +31:30:06.66 13.59  960.5  978.4   0.78  -1.07   1.21
# Mean  dx= 1.0915/1.4499  dy= -0.3127/1.4632  dxy= 1.8041
# Mean dra= -0.9669/1.2849  ddec= -0.2007/0.9435 sep= 1.1639
In the table, the first column is the star identifier. The second, third, and fourth columns are the catalog right ascension, declination, and magnitude for the star. The next two columns are the center X and Y coordinates of the center of the star in the image. The last three columns are the offset of the catalog position from the image star center in arcseconds in the right ascension and declination directions (horizontally and vertically) and radially.

The verbose mode gives more information about how the fit is going: 

$ immatch -vc gsc -i 5000 testx90mwg.fits

Last updated 25 March 1999 by Doug Mink dmink@cfa.harvard.edu

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