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4 The Mask Fabrication Process

Below are the steps necessary to make the masks. Since significant manpower costs are involved in producing these masks, the Observatory cannot supply unreasonable numbers of masks to meet every conceivable situation which may arise during an observing run. It is felt among the staff experienced with multi-slit observations that six masks per night is ample for most programs. The observer need only be concerned with obtaining the astrometric positions and running the trial solutions for the slitlet pattern.

  1. Accurate coordinates of the program objects must be obtained from the Sky Survey or other suitable material (CCD frames) to 0.1 to 0.3 arc-second precision (see Section 2). It is important to have a true astrometric solution including any secondary standards as may be needed. Taking short-cuts, such as creating fictitious "astrometric coordinates" from CCD xy positions, usually ends up wasting everyone's time and can cause some real surprises on that first night at the telescope.

  2. Running the MSLIT program is most profitably done by the observer so that the various trade-offs for the design of the pattern can be seen firsthand. Several trials per plate are usually required with appropriate changes in the data file.

  3. After the TRIAL solutions have been completed, a final DRILL run is done by a member of the support staff. The printouts and plots are cataloged for archival and data reduction purposes.

  4. The next step is the preparation of specially formatted (gerber) file of the pattern dimensions for a vendor. The final masks are photo-etched using technology from the printed circuit card industry. After chemical blackening, the masks are ready for immediate use at the telescope.

  5. As can be seen, the production of aperture plates is a laborious process. Therefore, observers are requested to submit their MSLIT data files (input files) to Jim De Veny THREE weeks before the run.


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Next: A Sample Run - MSLIT
Previous: The Extractions

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Updated 16Feb1996