In order to perform AO observations on an object a guide star of sufficient brightness is required.

This search tool will help the observer locate a star in the vicinity of the target that satisfies a given magnitude limit. Input targets can be given in the fields below, one target on each line, or you can load and submit a prepared target list. The program uses the USNO2.0 catalogue. The magnitude referred to as V magnitudes is the actually the average of the USNO2.0 R and B magnitudes.

The input format is quite flexible, but some limitations apply. Generally the format is: "Target_name Right_ascension Declination Epoch". The target name is optional, and so is the Epoch. If no epoch is specified the default can be changed from J2000 to B1950. Bear in mind the following limitations. 1) The target name cannot contain whitespace. 2) The declination must be prefixed by a sign (to separate it from the RA). 3) Epoch can obly be J2000 or B1950.

NB: The search may take a while for long input lists.