MM-MOS at the TNG


Mask preparation using target lists (``blind mode'')

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 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.  An example of mask setup using DRAW_MASK.SM
Using Skycat to check target sub-samples 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 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. 


The main output files for each mask will be:
a mask-cutting drawing in the standard Drawing Interchange File Format (DXF), for instance AOT9_123_01.dxf
a documentation file (e.g., AOT9_123_01 .log) and two postscript charts.

When all masks are ready, pack all files in one gzipped-tar file (e.g., piname_AOT9_123 .tgz) and notify the DOLoRes Staff Astronomer who will provide file transfer instructions. Masks need to be manufactured by TNG mechanics staff well in advance of the run. Do not forget to specify the requested slit width (1.1 or 1.6 arcsec) for each mask.
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