Spectroscopic observations must also be linearized as described in §6. A convenient environment in which to conduct this and the remainder of the basic cross-dispersed grism reduction is provided by the redxspec task. The redxspec task is the cross-dispersed grism equivalent of the redimage task used for imaging data reduction and the redgspec used for long-slit grism reduction. For example, to linearize a set of images obtained with a 180 sec exposure time, first form a list file of the image filenames using the csplist task by typing
csplist time 180 images=@allfiles > 180files
redxspec overwrites the input images so copy the input images to temporary files and work on these. This can be done by typing
imcopy @180files @180files//t
Now use epar to set the redxspec parameters as listed below.
I R A F
Image Reduction and Analysis Facility
PACKAGE = caspir
TASK = redxspec
(images = @tfiles) List of CASPIR input images
(spectru= ) Base name of spectrum file
(linear = yes) Linearize data?
(combine= no) Combine individual 2D spectra?
(flatten= no) Divide by flatfield?
(fixbad = no) Fix known bad pixels?
(clean = no) Interactively clean additional pixels?
(transfo= no) Straighten orders and subset?
(illumin= no) Correct non-uniform slit illumination?
(extract= no) Extract 1D spectra?
(fluxcal= no) Flux calibrate spectra?
(merge = no) Merge spectrum segments?
(flatdiv= no) Divide by flat spectrum star?
(plot = no) Plot merged spectra?
(bias = bias) Bias frame to use
(dark = dark180) Dark frame to use
(obstype= abba) Type of observation made
(zerosec= [190:195,10:90]) Zero level image section
(flatfil= ) Flatfield frame to use
(badfile= caspirdir$grism) Bad pixel file
(badtype= interp) Type of bad pixel correction
(illfile= ) Illumination frame to use
(reffile= ) Comparison extraction reference file
(fluxspe= ) Flux calibration spectrum to use
(weights= ) Merge weighting function file to use
(flatspe= ) Flat spectrum star file to use
(verbose= yes) Verbose output?
(imglist= )
(mode = ql)
The flags linear, combine, flatten, fixbad, clean, transform, illumination, extract, fluxcal, merge, flatdiv, and plot define the reduction steps that will be performed. The remainder of the parameters are used in the execution of these basic functions.
The parameters relevant to the linearization of a particular dataset are bias and dark. These are used in the same way as described in §6 for redimage.