Building Sequence Database Files for the Hopkins Ultraviolet Telescope

When you have selected 1 to 3 guide stars, edit the SDF and change the "no" to "yes" beside each of the selected stars, using the HST guide star ID number as a cross reference. You may find it useful to mark the selected stars on the clear overlay with a viewgraph marker for future reference. All materials should be returned to the target folders when you are finished. The information you enter on the guide stars will be used in the observation set-up to produce fiducial marks on the HUT TV at the expected positions of guide stars. (This information is also used by our s/w that produces the Target Book pages to mark the guide stars on the field image -- see section 4.)

The BUILDSEQ program also uses magnitude information to set the TV camera settings appropriately for locating the object and for guiding. Because most targets are stellar and continuum sources, BUILDSEQ uses Target_V_Mag (rounded down to the next fainter integer magnitude) to calculate the TV settings for locating the object. Likewise, the program averages the guide star magnitudes, and chooses the next lower integer magnitude for calculating the TV settings for guiding. In certain instances, it will be advantageous to override these default calculations and specify directly the magnitudes you want BUILDSEQ to use. For instance, emission line objects or extended nebulae may not have appropriate V magnitude information. In these cases, you should enter the optional line "TV_target_mag" into your SDF and fill in an appropriate V magnitude (presumably the desired guide star magnitude so that the guide stars will be visible during the set-up). There may also be cases where the average magnitude calculation from the guide stars needs to be overridden; this can be done with the optional parameter "TV_guide_star_mag". Let's say you had a situation with two relatively bright guide stars (V=11.8 and 12.1) that weren't very close to the object, and one fainter guide star (V=14.3) that was well placed near the object; you decide you want to make sure the fainter star is visible for the set-up. Left to its own devices, BUILDSEQ will choose V=13 for the set-up. You could specify "TV_guide_star_mag" to be 14 in order to skew the set-up toward the fainter star.