adjust-map

adjust-map uses a comparison arc image to make small corrections to the mapping created by map-spectra.

USAGE
 adjust-map  -m mapfile  -f framename[s]
INPUT
 mapfile.map is the name of an existing map file
framename[s] is one or two sets of image files with images of a comparison arc
OUTPUT
 framename.map is a new mapfile
PARAMETERS
linelist
 file with list of comparison lines to use
search_height
 half-height (in pixels) of region searched for line
search_width
 half-width (in pixels) of region searched for line
slit_width
 width of slit (in pixels)
ord_disp
 order of fit to adjustment along wavelength axis
ord_sag
 order of fit to adjustment along slit length axis



Details:

Using an existing spectral map, adjust-map searches in the region of each spectral line to calculate an offset. All offsets for one spectrum are fit to a  polynomial  which is used to correct the polynomial solutions in the spectral map. Take care if using higher order fits: unless you have very many comparison lines you may make things worse rather than better.
The parameters search_height and search_width should be set with care. If set too large, the line search may find the incorrect line- either a neighboring comparison line in the same spectrum, or a line in an adjacent spectrum. If the initial map errors are comparable to the spacing between comparison lines and/or spectra, begin with a value of the search parameters which is sufficiently small so that no misidentifications will occur, and iterate the solution several times until it converges.
If the initial errors are expected to be large (greater than a few pixels) you may want to use spectral-map to produce an overlay of the predicted positions before and after each iteration.

It is often useful to interpolate between two comparison arc exposures which, for example, bracket an object spectrum. If two framenames are provided, the map adjustment is the mean of that of the two frames. The output mapfile name is a composite of the two framenames; e.g.  from ccd0029 and ccd0030, a mapfile ccd0029-30.map is produced.

Suggested fit order is 5 for ord_disp, 1 for ord_sag.

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