| This document presents
an overview of MOS mask design based on lists
of objects with accurate celestial coordinates (from pre-existing images
and astrometry). Detailed instructions are provided with the software.
In order to allow accurate centering of the masks, the coordinates must
have relative precision of 0.2 arcsec or better. Compliance with
this technical constraint is responsibility of the Visiting Astronomer. |
| Targets are listed
in plain ASCII files which contain the identifiers and coordinates of all
potentially interesting objects in the field. The targets can extend over
a region larger than a mask, since the software allows spatial selection
within each mask. |
| The first two records
in each target list represent two reference stars
needed for mask pointing. Their coordinates must be on the same reference
system as the science targets. Further, they must be relatively
bright (e.g., V=16-18) in order to be easily marked on the short
exposure image used for telescope pointing. |
| The first time
the program TNG_MASKS is
run (with the ``design'' option), several
files are created for each mask as useful tools for target selection. From
now on, each mask will be treated separately. |
| The SuperMongo
script
draw_mask.sm
is used to verify that the targets do not produce overlap between the spectra.
In the output graph, the spectra are plotted as they are seen on DOLoRes
images, i.e. N is up, E to the right. The red side of the spectra
is to the left. The
individual slit lengths and the object location on the slits are iteratively
adjusted by editing the mask target lists. |
 |
 |
Also, the
Skycat
tool can be used to overplot each mask target list onto a DSS image (or
your astrometric image). Note that only the target centers are plotted.
The Skycat commands are helpful to further select target subsamples. |
| Once the target
selection is finalized for each mask, TNG_MASKS
has to be run again using the final target list (``write
mask'' option). This step includes creation of the actual mask manufacturing
file AOTx_XXX01_z.DXF. |
| Finally, the draw_mask.sm
script is used to record the final setup for each mask as a postscript
hardcopy. A finding chart should also
be printed using Skycat. Both are essential for mask pointing at the telescope. |
