Top/Reduction/How to Apply Distortion Map


** How to Apply the Distortion Map File [#k5291a01]
The distotion map can be simply applied by IRAF ccsetwcs command;
#pre{{
ccsetwcs (image file) (s11a-band.db) (s11a-band.coo)
}}
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** How the Files are Made [#s04301e7]
The distortion map is measured using the data of galactic plane, where the number density of stars are high.~
The coordinates of the detected stars are matched with those in the 2MASS catalog (which are written in s11a-band.coo), and the distortion map (s11a-band.db) is produced by IRAF ccmap command with 5th order polynominal; 
#pre{{
ccmap s11a-band.coo s11a-band.db lngunit="degree" latunits="degrees" projection="tnx" xxorder=6 xyorder=6 yxorder=6 yyorder=6 maxiter=3 reject=4
}}
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