ARTDATA: Making artificial slitless spectroscopy images

Frank Valdes wrote on Oct 29, 1998

Q:	I am trying to simulate slitless spectra, and for that purpose
I have thought to use mk2dspec, with an appropriate set of 1d input
spectra. However the problem I am finding is that, while I can easily
move the template spectrum around in the X coordinate by changing the
"center" parameter in the "model" file I have not figured out (by
reading the docs!) how to shift them around in the Y direction (to
simulate, in the case of a slitless system, the different positions of
different stars).

	Is there a way of using mk2dspec to do this? Or alternatively,
is there some other tool which could be used for this?


A:  Since there are no specific tools in IRAF for slitless spectroscopy
there are also no tools for simulating such data.  The main problem is
that APEXTRACT currently requires the spectra to run the entire length
of the 2D format and so this is basically what MK2DSPEC produces.
Someday I hope to work on the slitless spectroscopy problem.

This is not to say you can do something along the lines of what you
want.  What I suggest is you use MK2DSPEC to make you artificial
spectra at the resolution and size you want without noise.  You might
want to do something to taper the ends of this to simulate the fall off
of the response at the ends of the spectrum (this might be easiest in
the 1D spectrum used as input to the MK2DSPEC).  Then use MKPATTERN to
make a blank (all zero) template image of the size for the slitless
exposure.  Then use IMCOPY to copy all or pieces of the MK2DSPEC image
to parts of the MKPATTERN image, for example:

	ar> imcopy mk2dspec slitless[121:220,40:49]

where mk2dspec is 100x10 (the size of the output section must match the
size of the input which could also include a section to make the input
smaller).  After you have pieced together what you want on the output
you could then use MKNOISE to add noise and a background.  All this
would be easiest to develop and add to by using a CL script.

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Last post on Oct 29, 1998