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2.2.6 Selection Rules for "Drilled" Objects

Frequently, while running trial aperture plate solutions, difficulties arise getting all the high weight objects "drilled". Below is a list of possible reasons why an object may NOT be "drilled".

  1. The slitlet may be competing for space with an object of higher weight. The higher weight object will be selected.
  2. The slitlet may lie on or beyond the limiting radius for the mask. The radius is 23.60mm (156.3 arcseconds) for the RC Spectrograph and Cryogenic Camera. Moving the field center coordinates (central object) or decreasing SKYRAD may correct the problem. Slitlet lengths less than the default, however, are not generally recommended as this will limit the amount of sky available for good sky subtraction.
  3. The slitlet may lie within 3.0 arc-seconds of another object(any weight). To prevent contamination from nearby objects, no slitlets may be "drilled" within this radius of another object regardless of weight. Removing one of the conflicting objects from the data file may "solve" the problem.
  4. Occasionally the program will run but will not produce a solution resulting in all objects winding up in the undrilled list. If the field is sufficiently crowded, it may not be possible to drill the setup stars without hitting one of the targets in the list. Setup holes have the highest priority on a mask and if one of them cannot be drilled no solution is possible. Changing the field center or deleting the conflicting object may fix the problem.
  5. Difficulties can arise when too many restrictions are placed on a field and may result in no solution. For example, setting the position angle to 90° and having setup stars of similar RA could result in no solution. The setup stars and possibly the field center(if non-zero weight) would all compete for the center line of the mask.


kessel@noao.edu
Fri Jun 23 09:48:03 MST 1995