| filename
| Name of FITS or IRAF image file. This must be present.
|
| -a rotation angle
| Initial WCS rotation angle in degrees. This angle is used in the nominal
plane tangent WCS used to match references stars with image stars and as the
initial value for the fit. (default 0)
|
| -b RA Dec
| Initial center right ascension and declination in degrees or
sexigesimal in B1950 (FK4). Sexigesimal coordinates are
hours:minutes:seconds degrees:minutes:seconds.
This center is used in the nominal plane tangent WCS used to match
references stars with image stars and as the initial value for the
fit. (default RA, DEC, and EPOCH keywords in
the image header).
|
| -c name
| Reference catalog (GSC, USAC, UAC, or
Starbase table filename)
|
| -d name
| Use this DAOFIND-format output catalog of X, Y, and magnitude instead
of searching for stars in the image. The format is simply
white-space-separated numbers on a line, with # at the beginning of comment
lines. The fourth and later columns are ignored. The file should be sorted
by magnitude, as a number of sources no greater than the number of catalog
sources will be used, unless the -s option is used to increase the proportion
of the larger of catalog or image sources used.
|
| -e
| Erase the old WCS projection from the image header before reading an
initial WCS from it. This is useful when there is an error in the initial
CRVALs and CDELTs or CD matrix and you just want to ignore them and use
either the RA, Dec, SECPIX and image center or values from the imwcs command
line.
|
| -f
| Write FITS output whether the imput image is FITS or IRAF .imh.
|
| -g class
| Guide Star Catalog object class (-1=all,0,3 (default -1)
|
| -h number
| Maximum number of reference stars to use (10-200, default 25).
(Added in version 1.7)
|
| -i value
| Set the minimum peak value for a star in image. If value is
less than zero, the minimum peak is -value image pixel standard
deviations. Setting this number rejects faint stars early in the
selection process for a significant saving in computing time.
|
| -j RA Dec
| Initial center right ascension and declination in degrees or
sexigesimal in J2000 (FK5). Sexigesimal coordinates are
hours:minutes:seconds degrees:minutes:seconds.
This center is used in the nominal plane tangent WCS used to match
references stars with image stars and as the initial value for the
fit. (default RA, DEC, and EPOCH keywords in
the image header).
i
|
| -l
| Reflect image left <-> right before rotating and fitting WCS
|
| -m mag1 [mag2]
| Initial reference star faint and bright limiting magnitudes if two numbers
are given or faint magnitude limit, if only one number is given. Order does
not matter. (Second magnitude limit added in version 1.7)
|
| -n number
| Fit number parameters to a plane tangent WCS (default is 4).
If a single digit is given, 2= center, 3= center + plate scale ,
4= center + plate scale + rotation, 5= center + rotation + X plate scale
+ Y plate scale, 6= center + CD matrix, 8= center + CD matrix + reference
coordinates. If 0, no fit is done, and the initial fit, from the command
line and/or the header is written to the header using the standard keywords.
Any parameters can be fit by specifying them in a single multi-digit
number, where 1= center RA, 2= center Dec, 3= X (or both) plate scale,
4= Y plate scale, 5= optical axis rotation, 6= chip-centered rotation,
7= reference pixel X, and 8= reference pixel Y.
If number is negated, a second fit is run rejecting matches
which miss the fit by more than two sigma in radius.
If n is 0, no fit is attempted, and header parameters
are used to insert a default world coordinate system: CRPIX1 and CRPIX2
are assumed to be the center of the image, unless they are already in the
header or set on the command line. RA and DEC are used
for CRVAL1 and CRVAL2, respectively, unless a different
value is entered on the command line. CDELT1 and are
set to identical values based on an arcseconds/pixel plate scale from the
command line -p or the SECPIX, SECPIXi, or
PIXSCALi keyword values. Rotation, CROTAi is set to
be 0 unless it is set by the -a command line option.
| -o [filename]
| Write output to the file in the next argument. If another argument
preceded by a "-" follows, WCS parameters are added to the input file.
The default is to write to a new file named by adding a w to
the root of the input filename, keeping the same file extension. Thus,
in the default mode, the WCS-added version of test.fits is
written to testw.fits.
|
| -p plate scale
| Initial plate scale in arcseconds per pixel. This is used when
matching iamge and reference stars and as an initial value for the fit.
(default SECPIX or SECPIX1 and SECPIX2 keywords
in the image header).
(default 0)
|
| -q option list
| Add optional processing steps:
- i: iterate. Use the first fit WCS to define the image area for a
second catalog search, star match, and WCS fit of the same parameters
as the first pass.
- p: polynomial. Fit a quadratic polynomial after fitting
a CD matrix or CDELTn asnd CROTA2. Residuals are usually improved,
and the first-fit WCS is saved in the header for programs which cannot
read the polynomial keywords.
- r: recenter. Use the WCS coordinates of the image center
as obtained by the first WCS fit (where the reference coordinates as
well as WCS value may have been fit) as the reference values for the
image center as the reference point for a second fit. This is done
after the second fit if -q i is set.
- s: sigma clip. Use only matches where the radial distance
between the reference star position and the matching image star position
using the first WCS fit was within two standard deviations of the mean.
This is reapplied after each iteration.
|
| -r rotation angle
| Rotate by this angle in degrees before fitting WCS. It must be a
multiple of 90 degrees. Initial values which are position related,
-a rotation angle (CROTA2 or CD), -p plate scale, if set in two dimensions,
and -x pixel coordinates of optical axis are set, and image coordinates for
stars to be matched must be computed, after this rotation is made.
(default 0)
|
| -s fraction
| If there are more image stars (ni) than reference stars found in
the image area (nr), match the nr reference stars against
fraction * ni image stars.
If there are more reference stars found in the image area than stars
found in the images, match fraction * nr reference stars
against ni image stars. This is useful if there is a spectral
mismatch between the image and the reference catalog so that the n brightest
stars in the image are likely to be quite different from the n brightest
stars in the reference catalog.
|
| -t offset tolerance
| Offset tolerance in pixels (default 10)
|
| -u match file
| Use this file of X,Y,RA,Dec matches to fit a WCS instead of trying to
automatically find stars and match them to a catalog. If a catalog is
specified, these matches are used to fit an initial WCS, before trying
to match image and catalog positions for a second fit. This command
used to specify a plate number from which to accept reference star
positions from USNO catalogs.
(Changed in of version 2.8.7)
|
| -v
| print more information about process
|
| -w
| Write new file or header (default is to compute the WCS without
writing it out)
|
| -x Xref Yref
| Pixel coordinates of the reference pixel used in the WCS projection
(Added in version 1.6)
|
| -y frac
| Multiply image dimensions by this for search (default 1.0)
The maximum number of reference stars used will be multiplied by the square
of this factor so that the density is the same as for image stars. Use this
if your center is uncertain by a significant fraction of the image size.
(Added in version 1.7)
| |
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[WCS programs]
[IMWCS]