extract-2dspec uses a
map file to extract 2-dimensional spectra from a set of image files.
Spectra are extracted onto a rectangular array of wavelength and slit
position.
Output data are stored as a set of image extensions in a 3-dimensional
fits
file, one spectrum per extension The 2-d file consists of two planes,
the first of which is the spectrum, and the second of which contains
the 1-sigma errors of the spectrum, pixel by pixel. extract-2dspec
automatically handles nod&shuffle data.
USAGE
extract-2dspec
-f framename -m mapfile
INPUT
framename
is a set
of image files from which the spectra are extracted
mapfile is the map file which
applies
OUTPUT
framename_2spec.fits
PARAMETERS
deltalambda
wavelength interval of extracted spectrum
deltaslit
slitposition interval of extracted
spectrum, in arc sec
minlambda
minimum wavelength of extracted spectrum
maxlambda
maximum wavelength of extracted spectrum
telscale
telescope scale arc sec/mm
search
half-width of spectrum
search region, in pixels
Details:
If the parameter search has a
non-zero value, one may optionally search for a shift in the mean slit positions of all spectra (such as might be
caused by less-than-perfect setup on the sky or by telescope drift).
This is necessary if multiple spectrum files are later to be combined
using sumspec,
particulary if CR rejection is used.
The header of the first spectrum contains the following parameters:
N_SLITS = number of slits extracted
D_SLIT = interval along slit, in arc seconds
CRVAL1 = wavelength of first pixel
CDELT1 = wavelength interval of pixels
EXPTIME = total exposure time of the spectrum
The headers of all spectra contain the following parameters:
CNTRLINE = the line in the 2-d spectrum centered on the object
OBJECT = object name, as defined in the SMF file
for the mask
SLITNUM = slit number in SMF file for the mask
Nod & shuffle data:
The shuffle region is extracted along with the primary slit region and
subtracted from the primary slit data