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How do I modify my FIF.tbl so that MOPEX makes my output mosaic the size of my choice?
Posted by z-Vandana Desai on 29 January 2009 11:04 AM
Here is an example FIF.tbl file, which is by default placed in your output directory by the MOPEX module Fiducial Image Frame.

********************************************************************************
\char comment = Output from fiducial_image_frame, version 1.4
\char Date-Time = Jan 28, 2009, 10:13:05
\real CRVAL1 = 217.950767
\real CRVAL2 = 34.074341
\real CRPIX1 = 2455.50
\real CRPIX2 = 2900.00
\real CROTA2 = 0.00000
\real CDELT1 = -6.92842E-04
\real CDELT2 = 7.21978E-04
\int NAXIS1 = 4910
\int NAXIS2 = 5799
\int EQUINOX = 2000
\char PROJTYPE = TAN
\char COORDINATE_SYSTEM = J2000
\char CTYPE1 = RA---TAN
\char CTYPE2 = DEC--TAN
\real EXTENT_X = 3.401852
\real EXTENT_Y = 4.186750
********************************************************************************

Let's say you wish to edit this FIF.tbl so that your mosaic ends up centered at RA = 218 degrees, DEC = 34 degrees, and you want your mosaic to be 1 degree on a side.

Then you would change the following values in your FIF.tbl :

CRVAL1 = desired reference RA of output mosaic in degrees = 218

CRVAL2 = desired reference DEC of output mosaic in degrees = 34

NAXIS1 = desired length of output rectangular region in pixels = | 1 degree / CDELT1 | = 1443

NAXIS2 = desired width of output rectangular region in pixels = | 1 degree / CDELT2 | = 1385

CRPIX1 = pixel coordinate corresponding to CRVAL1, usually the center of the mosaic
= ( NAXIS1 + 1 ) / 2 = 722

CRPIX2 = pixel coordinate corresponding to CRVAL2, usually the center of the mosaic
= ( NAXIS2 + 1 ) / 2 = 693

See this FAQ to learn how to use this information in conjunction with the MOPEX module mosaic_geom in order to make a small mosaic out of a set of BCDs that covers a large area.