Note: see the UCAC4 document, and the
the fix for high proper motion stars.
The UCAC home page is available at
Please acknowledge the usage
of the UCAC4
Note: SDSS is also available from http://www.sdss3.org/dr9/
Note: The column expnum provides an access to details on the exposures, and a link to the Preview and Retrieval System via the CADC