.help velset apr94 rvsao
velset -- Artificially change the redshift of spectra.
velset input output
This task changes the wavelength scale of spectra, moving them from one
given redshift to another one. The input spectra are specified by an
image template list. The output is either a matching list of spectra or
a directory. The task works by copying the input spectra to the output
destination, and then modifying the header keywords that describe the
wavelength axis, on the output spectra only. A spectrum may not be
copied onto itself; this prevents original wavelength information from
being accidently overwritten. Image sections are ignored both on input
and output, because it is assumed that the user wants a copy of the
input with the wavelength scale modified.
*** WARNING ***
Use this task on log-wavelength spectra ONLY
This task looks in the header for keywords describing the wavelength
axis; keywords are sought in the following order: first, IRAF keywords
'W0' and 'WPC'; next, CD keywords 'CRVALn' and 'CDn_1'; and finally,
FITS keywords 'CRVALn' and 'CDELTn' (n is the value of task parameter
'axis', unless the IRAF header keyword 'DISPAXIS' is found, in which
case it takes precedence over the parameter). Logarithmic wavelength
scale is treated correctly if either the 'log' task parameter is set to
"yes" or if the IRAF header keyword 'DC-FLAG' is found in the header
with value 1. 'HISTORY' records are appended to the header.
.ls input [file name template]
Name(s) of the input files containing spectra.
.ls output [file name or directory name]
The output file, or directory, to which the transformed spectra will be
Is the new redshift in Z (yes) or km/sec (no)
.ls newz = 0.0
The redshift of the output spectra.
.ls (verbose = yes) [boolean]
If set to "yes", the wavelength origin and step for
both the input and output spectra are listed as the task progresses.
1. Transform a set of spectra with root name 'cluster*'
to redshift 0.0. The result will be stored in subdirectory
'local/'. The input spectra are in STSDAS format (extension
to> setvel cluster*.hhh local/ newz=0.0
Source Code · Search Form · STSDAS