.help specshift Oct92 noao.onedspec
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NAME
specshift -- Shift dispersion coordinate systems
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USAGE
specshift spectra shift
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PARAMETERS
.ls spectra
List of spectra to be modified.
.le
.ls shift
Dispersion coordinate shift to be added to the current dispersion coordinate
system.
.le
.ls apertures = ""
List of apertures to be modified.  The null list
selects all apertures.  A list consists of comma separated
numbers and ranges of numbers.  A range is specified by a hyphen.  An
optional step size may be given by using the 'x' followed by a number.
See \fBxtools.ranges\fR for more information.  This parameter is ignored
for N-dimensional spatial spectra such as long slit and Fabry-Perot.
.le
.ls verbose = no
Print a record of each aperture modified?
.le
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DESCRIPTION
This task applies a shift to the dispersion coordinate system of selected
spectra.  The image data is not modified as with \fBimshift\fR but rather
the coordinate system is shifted relative to the data.  The spectra to be
modified are selected by specifying a list of images and apertures.  If no
aperture list is specified then all apertures in the images are modified.
For N-dimensional spatial spectra such as long slit and Fabry-Perot the
aperture list is ignored.

The specified shift is added to the existing world coordinates.  For linear
coordinate systems this has the effect of modifying CRVAL1, for linear
"multispec" coordinate systems this modifies the dispersion coordinate of
the first physical pixel, and for nonlinear "multispec" coordinate systems
this modifies the shift coefficient(s).

It is also possible to shift the linearized coordinate systems (but not the
nonlinear coordinate systems) with \fBsapertures\fR or possibly with
\fBwcsedit\fR or \fBhedit\fR if the coordinate system is stored with a
global linear system.

The \fIverbose\fR parameter lists the images, the apertures, the shift, and
the old and new values for the first physical pixel are printed.
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EXAMPLES
1.  To add 1.23 Angstroms to the coordinates of all apertures in the
image "ngc456.ms":

.nf
	cl> specshift ngc456.ms 1.23
.fi
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REVISIONS
.ls SPECSHIFT V2.10.3
First version.
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SEE ALSO
sapertures, dopcor, imcoords.wcsreset, hedit, ranges, onedspec.package
.endhelp
