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.help awcspars Mar00 astcat
.ih
NAME
awcspars -- edit the default world coordinate system parameters
.ih
USAGE
awcspars
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PARAMETERS
.ls wxref = "INDEF", wyref = "INDEF"
The image header keyword names or the numerical values of the x and y reference
point in pixels. If wxref = "INDEF" and wyref = "INDEF" the reference
point defaults to the center of the image.
.le
.ls wxmag = "INDEF", wymag = "INDEF"
The image header keyword names or the numerical values of the x and y scale
factors in arcseconds per pixel. If wxmag or wymag = are undefined a new
wcs cannot be created.
.le
.ls wxrot = "180.0", wyrot = "0.0"
The image header keyword names or the numerical values of the x and y rotation
angles in degrees measured counter-clockwise to the positive x and y image
axes. The default orientation is east=left, north=up. Wxrot values of 0.0,
90.0, 180.0, and 270.0 correspond to east=right, up, left, and down
respectively. Wyrot values of 0.0, 90.0, 180.0, and 270.0 correspond to
north=up, left, down, and right respectively.
.le
.ls wraref = "RA", wdecref = "DEC"
The image header keyword names or the numerical values of the reference
point in celestial coordinates. If wraref and wdecref are undefined
a new wcs cannot be created.
.le
.ls wraunits = "", wdecunits = ""
The units of the reference point celestial coordinates. The options are
"hours", "degrees", and "radians" for the ra coordinate and "degrees"
and "radians" for the dec coordinate. If wraunits and wdecunits are undefined
they default to the preferred units of the reference system.
.le
.ls wproj = "tan"
The sky projection geometry. The most commonly used projections are "tan",
"arc", "sin", and "lin". Other supported projections are "ait","car", "csc",
"gls", "mer", "mol", "par", "pco", "qsc", "stg", "tsc", and "zea".
.le
.ls wsystem = "EQUINOX"
The image header keyword name or string defining the celestial coordinate
system of the reference point. The most common values for wsystem are
"2000.0", "1950.0", "J2000.0", and "B1950.0". Type "help ccssytems" to get
a full list of options.
.le
.ih
DESCRIPTION
The default wcs parameters are used to create an approximate FITS wcs for
an images which do not have one. Creating an approximate header
from the telescope pointing position and the known scale and orientation
of the detector can make later steps like locating the catalog stars
for computing an accurate plate solution simpler.
In coordinates of the reference point in pixels and celestial coordinates
\fIwxref\fR, \fIwyref\fR, \fIwraref\fR, \fIwdecref\fR, the scale factors
\fIwxmag\fR and \fIwymag\fR, and the orientation \fIwxrot\fR and \fIwyrot\fR
can be read from the image header or set by value. The coordinate system
and units of the celestial coordinates of the reference point \fIwsystem\fR
and \fIwraunits\fR and \fIwdecunits\fR must be set explicitly. The image
projection function \fIwproj\fR must also be set separately.
.ih
EXAMPLES
1. List the default wcs parameters.
.nf
cl> lpar awcspars
.fi
2. Edit the default wcs parameters.
.nf
cl> awcspars
... edit the parameters in the usual way
... type :wq to quit and save the edits
.fi
3. Edit the default wcs parameters from the agetim task.
.nf
cl> epar agetim
... edit the agetim parameters
... move to the agetim parameter line and type :e
... edit the awcspars parameters
... type :wq to quit and save the awcspars edits
... continue editing the remaining awcspars parameters
... type :go to execute the task
.fi
4. Save the current awcspars parameter values in a text file called
awcs1.par. Use the saved parameter set in the next call to the agetim
task.
.nf
cl> epar awcspars
... edit some parameters in the usual way
... type :w awcs1.par
... type :q to quit
cl> agetim ... awcspars=awcs1.par ...
.fi
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TIME REQUIREMENTS
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BUGS
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SEE ALSO
agetim, ahedit
.endhelp
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