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Up: SUGGESTIONS FOR CREATING THE TARGET FIELDS

Sky Positions

• Select many (we mean lots, many more than will get assigned) sky positions so that fibers can get assigned to the desired number of them with minimal impact on the assignment to target objects.

• In cases where sky is important, but not dominating the signal, on the order of a dozen fibers should probably be assigned to observe the sky. It is ideal to measure blank sky positions in all cases, but random sky positions are probably OK in many situations. Try generating lists of a few hundred random coordinates located on the circumference of circles of varying radii (5 to 30 arc-minutes) centered on the field. The biggest danger of the random sky positions is the risk that a sky fiber will be placed on or near field stars, particularly in crowded fields.

• For objects that are fainter than the sky, more care is required to hand select blank regions of sky. Again, select many positions. Probably half of the fibers should be dedicated to sky. Designing your field to allow telescope beam switching may be beneficial for the best sky subtraction (unfortunately, we don't have any algorithms for generating beam switching configurations).