Plotting the USNO UCAC2 Catalog on a Telescope Image
Using SAOimage and imucac2

This SAOimage display shows the alignment of USNO UCAC2 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, saoucac2: saoimage -reg `imucac2 -r 10 $1` -wcscom sucac2_-ha_%s $1 where the argument to the task is the name of the file to be displayed. The immatch program will provide a list of the stars in the image which match catalog stars.

Click on the image for full-screen view

imucac2 finds all of the USNO UCAC2 Stars in the image based on the world coordinate system parameters in its header and writes them to the region file testx90mw.fits.ucac2, 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 UCAC2 Catalog Stars (10" radius) CIRCLE(737,763,16) # ucac2 243.072534 CIRCLE(661,661,16) # ucac2 243.072535 CIRCLE(960,978,16) # ucac2 244.071712 CIRCLE(283,620,16) # ucac2 243.072550 CIRCLE(948,475,16) # ucac2 243.072529 . . . CIRCLE(230,196,16) # ucac2 243.072555 CIRCLE(607,773,16) # ucac2 243.072537 CIRCLE(18,666,16) # ucac2 243.072565 CIRCLE(986,507,16) # ucac2 243.072527 CIRCLE(209,861,16) # ucac2 243.072558

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:

sucac2 3.5, 22 August 2003, Doug Mink SAO  Find closest star
     ucac2 16:15:56.174 +31:24:23.36 J2000 r= +00:15:00.0 at epoch 2000.0000
UCAC2_num     RA2000       Dec2000      MagJ   MagH   MagK   MagC  Arcsec
243.072538  16:15:52.975 +31:25:15.55  13.72  13.29  13.23  14.78   66.34