Plotting the UCAC3 Catalog on a Telescope Image
Using SAOimage and imucac3

This SAOimage display shows the alignment of USAC3 stars with a test image after a world coordinate system has been fit. The coordinates plotted are based on header keywords describing a plane-tangent system fit by matching HST Guide stars and sources found in the image. This image was produced by a one-line Unix shell script for this task, saoucac3: saoimage -reg `imucac3 -r 10 $1` -wcscom sucac3_-ha_%s $1 where the argument to the task is the name of the file to be displayed. The immatch program can provide a list of the stars in the image which match catalog stars.

Click on the image for full-screen view

imucac3 finds all of the UCAC3 stars in the image based on the world coordinate system parameters in its header and writes them to the region file testx90mw.fits.ucac3, seen on the right. The name of this file is sent to standard output which the backquotes give to SAOimage as a command line argument following the -reg command.

# USNO UCAC3 Catalog Stars (10" radius) CIRCLE(661,661,16) # ucac3 243.117000 CIRCLE(960,978,16) # ucac3 244.112573 CIRCLE(737,763,16) # ucac3 243.116998 CIRCLE(283,620,16) # ucac3 243.117018 CIRCLE(948,475,16) # ucac3 243.116990 CIRCLE(900,395,16) # ucac3 243.116992 CIRCLE(589,526,16) # ucac3 243.117004 CIRCLE(817,653,16) # ucac3 243.116996 CIRCLE(230,196,16) # ucac3 243.117027 CIRCLE(19,666,16) # ucac3 243.117040 CIRCLE(986,507,16) # ucac3 243.116988 CIRCLE(607,772,16) # ucac3 243.117003 CIRCLE(848,786,16) # ucac3 243.116995 CIRCLE(529,33,16) # ucac3 243.117007 CIRCLE(31,921,16) # ucac3 243.117039 CIRCLE(867,236,16) # ucac3 243.116994 CIRCLE(178,795,16) # ucac3 243.117031 CIRCLE(261,28,16) # ucac3 243.117022 CIRCLE(209,861,16) # ucac3 243.117030

If the w key is struck when the SAOimage cursor is centered on the galaxy in the middle of this picture, the following appears on the user's terminal:

sucac3 WCSTools 3.8.0, 13 November 2009, Doug Mink SAO  Find closest star
     ucac3 16:15:56.228 +31:24:23.98 J2000 r= +00:15:00.0 at epoch 2000.0000
Number       RA2000       Dec2000       MagB   MagR   MagI   MagJ   MagH   MagK   MagM   MagA nim ncat  Arcsec
243.117004 16:15:52.975 +31:25:15.50   15.76  14.78  14.27  13.72  13.29  13.23  15.14  15.07   2    2   66.25