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Guide Star Catalogues

Any of the optical catalogs searchable in the Observing Tool (UCAC2, USNO-A/B, GSC-1/2, CADC or ESO) are acceptable for selecting guide stars for the optical wavefront sensors.  Our tests have shown that the catalog with the best combination of photometry, astrometry, and exclusion of extended sources is the UCAC2.  Therefore, we recommend using this catalog whenever possible. Unfortunately, the sky coverage of the UCAC2 is not complete for declinations greater than +45 degrees (the all-sky UCAC3 is due to be released in 2008), and many of the stars in the UCAC2 are not bright enough for use with the PWFSs.

The Guide Star Catalogues at ESO and CADC tend to list the brighter guide stars in the other catalogues, that are usually bright enough for PWFS2, which is normally used for NIRI f/6 and MICHELLE observations. Deep catalogs such as GSC-2 or USNO-B are useful for selecting faint natural guide stars for use in the ALTAIR + laser guide star mode.

The near-IR 2MASS catalog must be used for selecting guide stars for the near-IR on-instrument wavefront sensors in NIFS or GNIRS.  This catalog should not be used to select stars for the optical WFS.