1imwcs(1) General Commands Manual imwcs(1)
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6 imwcs - Set WCS in FITS and IRAF image files
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9 imwcs [options] FITS or IRAF filename
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12 imwcs (pronounced im-W-C-S) is a utility for setting the world coordi‐
13 nate system (WCS) of a FITS or IRAF image. The WCS is the relationship
14 between sky coordinates and image pixels and can be described in a
15 standard way in the header of an image. The program was originally
16 written at the University of Iowa, but has been adapted and amplified
17 by Jessica Mink at the Smithsonian Astrophysical Observatory.
18 imwcs currently works only on images where the rotation about the cen‐
20 ter is known to within a few degrees It has been tested extensively
21 only on images with near-zero rotation.
22 A plane-tangent projection (center right ascension and declination,
24 plate scale, and rotation angle) is fit based on matches between stars
25 in the image and stars in a reference catalog. The HST Guide Star Cata‐
26 log, the USNO A 1.0, SA 1.0, or UJ Catalog, or a user-supplied, tab-de‐
27 limited Starbase catalog may be used.
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31 -a <angle>
32 Initial rotation angle in degrees (default 0)
33 -b <RA> <Dec>
35 Initial center in B1950 (FK4) RA and Dec (default=RA,DEC from
36 file)
37 -c <catalog name>
39 Reference catalog (gsc(=HST GSC), ua2(=USNO-A2.0), TMC(=2MASS
40 Point Source Catalog), gsc2(=GSC II), ub1(=USNO-B1.0), local
41 file, etc.)
42 -d <catalog name>
44 Use this DAOFIND output catalog of X, Y, and magnitude instead
45 of searching for stars in the image. The format is simply
46 white-space-separated X, Y, and magnitue on a line, with # at
47 the beginning of comment lines.
48 -e Erase image WCS keywords, getting initial WCS from command line
50 -f Write FITS output no matter what input
52 -g <class>
54 Guide Star Catalog class (-1=all,0,3) (default -1)
55 -h <number>
57 Change the maximum number of reference stars to match from 25 to
58 -i <counts>
60 Minimum peak value for star in image. If negative, use
61 -<counts> standard deviations as minimum.
62 -j <RA> <Dec>
64 Initial center in J2000 (FK5) RA and Dec (default=RA,DEC from
65 file)
66 -k <magnum>
68 Use this magnitude to sort brightest catalog stars.
69 -l Reflect left<->right before rotating and fitting
71 -m [<bright magnitude>] <faint magnitude>
73 Limiting catalog magnitude(s) (default none, bright -2 if only
74 faint is given)
75 -n <number>
77 Number of parameters to fit (1-8, or digit string). The default
78 is 2 (RA+Dec) if <3 stars are matched, 3 (RA+Dec+scale) if <5
79 stars are matched, or 4 (RA+Dec+scale+rot) if 5 or more stars
80 are matched. Alternatively this may be a list of all of the pa‐
81 rameters to fit, in the form nnnnnn.., where 1=RA, 2=Dec, 3=RA
82 scale, 4=Dec scale, 5=rotation angle, 6=Y axis rotation (CD ma‐
83 trix), 7=RA reference pixel, and 8=Dec reference pixel.
84 -o <filename>
86 Write output to this file; may be the same as input file. This
87 option automatically sets the -w option to write the file.
88 -p <scale>
90 Initial plate scale in arcsec per pixel (default 0)
91 -q <option list>
93 <i>terate, <r>ecenter, <s>igma clip, <p>olynomial, <t>olerance
94 reduce (half for each iteration). A number following an option
95 repeats the option that many times.
96 -r <angle>
98 Rotation angle in degrees before fitting (0, 90, 180, 270) (de‐
99 fault 0)
100 -s <frac>
102 Use this fraction extra stars (default 1.0)
103 -t <num>
105 Offset tolerance in pixels (default 20)
106 -u <file>
108 File of X Y RA Dec assignments for initial WCS
109 -v Verbose listing of processing intermediate results
111 -w Write WCS to a new file (default is read-only) -x X and Y coor‐
113 dinates of reference pixel (default is image center) -y multiply
114 image dimensions by this for search (default is 1) -z Use AIPS
115 classic projections instead of WCSLIB; use CD matrix or CDELT
116 instead of polynomial solution.
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120 http://tdc-www.harvard.edu/software/wcstools/imwcs/
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124 Jessica Mink, SAO (jmink@cfa.harvard.edu)
12530 January 2003 WCSTools imwcs(1)