We suggest that DEIMOS slitmask observers who are observing fields
near the Galactic poles come prepared with a set of finder charts
which show the alignment stars and targets to which slits have
been assigned. Such charts are helpful in case the
coarse-alignment stars are not visible on the guider, which can
happen on sparse fields. This document describes how to create
them using the IDL program dsim2regions.
Requirements
To generate these files you will need the following:
A FITS image of the field with astrometric data encoded
in the image header using appropriate World Coordinate System
(WCS) keywords. One way to create such an image is by using
the various WCS-related tasks in the
images.imcoords package of IRAF.
A mask design file (FITS format) generated by the DEIMOS
mask design program DSIMULATOR.
Put the two data files in the same directory as your mask
design file.
Launch IDL.
Create a ds9 regions file in IDL via
dsim2regions, 'foo.fits', 'foo.regions', /LABEL
Use the ds9 image
display tool to open your WCS-enabled FITS image of the
field.
Use the Region > Load Regions... option in
ds9 to open the regions file you created. The slits and
targets should be drawn and labeled, and the FOV of the
guider and DEIMOS should be outlined.
Use the File > Save As > Image option in
ds9 to write the resulting image out as a JPG or PNG file.
