Plotting the USNO-A2.0 Catalog on a Telescope Image
Using SAOimage and imua2

This SAOimage display shows the alignment of USNO-A2.0 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, saoua2: saoimage -reg `imua2 -r 10 $1` -wcscom sua2_-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

imua2 finds all of the USNO-A2.0 Stars in the image based on the world coordinate system parameters in its header and writes them to the region file testx90mw.fits.ua2, 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 A-2.0 Catalog Stars (10" radius) CIRCLE(529,34,16) # ua2 1200.07808132 CIRCLE(661,661,16) # ua2 1200.07807424 CIRCLE(959,979,16) # ua2 1200.07805842 CIRCLE(738,764,16) # ua2 1200.07807023 CIRCLE(208,882,16) # ua2 1200.07809784 . . . CIRCLE(746,33,16) # ua2 1200.07806967 CIRCLE(471,484,16) # ua2 1200.07808428 CIRCLE(95,901,16) # ua2 1200.07810388 CIRCLE(348,981,16) # ua2 1200.07809065 CIRCLE(394,701,16) # ua2 1200.07808825

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:

sua2 2.9.4, 29 June 2001, Doug Mink SAO  Find closest star
USNO A-2.0    16:15:56.256 +31:24:24.82 J2000 r= 120.00 at epoch 2000.00
USNO A2 number  RA2000       Dec2000     MagB  MagR Plate  Arcsec
1200.07808051 16:15:55.118 +31:24:22.11  17.1  16.9  330    14.82