Convenient charts for identifying offset guide stars for CASPIR observations of southern objects can be obtained using the COSMOS database at the AAO, or the southern Digitised Sky Survey.
To access the COSMOS database, telnet to the COSMOS machine at Epping by typing:
telnet cosmos.aao.gov.au username: cosmos password: UKSTcosmos
Enter your object coordinates into a text file one object per line in free-format, e.g.,
cat > input.dat 08 06 30.24 -10 18 50.0 21 52 58.01 -69 55 40.4 <cnrtl>d
Start the COSMOS program and take the defaults on all the questions except for those listed below:
cosmos >> Change default parameters (n)? y >> Min, Max BJ magnitude (0.00 25.00): 0.0 20.0 >> No. plots across, down page (1 1): 5 3 >> Please select an output device: 1 (postscript) >> Filename => output.ps >> Text output filename (<CR> for none): output.dat >> Input coordinate file (<CR> for none): input.dat (coordinate file) >> Equinox (J2000.0): B1950.0 >> Diameter of charts (6.0 arcmin): <CR> (good size) ... >> More plots (y)?: n
Now ftp the results (output.ps and output.dat) back to your home machine and print them. The COSMOS charts are contained in the file output.ps (e.g., Figure 18). The output.dat file is a text listing of source positions, brightnesses, etc. These can be used to calculate offsets to suitable guide stars in arcsec on the sky. The users guide for the COSMOS program can be found in the file /cosmos/disk1/doc/Userguide.tex. Contact Michael Drinkwater at the UKSTU for further information (mjd@aaocbn3.aao.gov.au).
Figure 18: Typical COSMOS charts for 
regions of sky.
The southern Digitised Sky Survey is best accessed via CDROM. The World Wide Web SkyView Basic (http://skyview.gsfc.nasa.gov/skyview.html) or STScI (http://stdatu.stsci.edu/dss/dss_form.html) nodes can also be used, but these can be slow and the file headers differ from those of the CDROM versions. Convenient lists of stars from the Hubble Guide Star Catalog within a specified radius of an object (specified by name or coordinate) can be obtained from the ESO web site (http://archive.eso.org/gsc/gsc). SkyView Advanced (http://skyview.gsfc.nasa.gov/cgi-bin/v3.0/skyview_advanced.pl) can also be used to select Digitized Sky Survey images by specifying object names, overlay HST Guide Star Catalog stars as well as many other cataloged objects, and print the image and coordinates of overlayed objects in one streamlined, but slow, process.
To extract a Digitized Sky Survey image from CDROM type
getimage and follow the instructions for loading the relevant
CDROM disk.
When all the FITS files have been obtained, enter the filenames into a text file one per line, e.g.:
cat > files.dat 3c195.fits 2152-699.fits <cntrl>d
Then form a postscript mosaic of these images using DSSPLOT (e.g., Figure 19) by typing:
dssplot files.dat
DSSPLOT is part of the CASPIR IRAF package. Refer to §6 for information on how to obtain copies of this package. Print the mosaic by typing, e.g.:
lpr -s -Plaser_d dssplot.ps
Figure 19: Typical southern Digitised Sky Survey charts formatted with DSSPLOT.
Positions of objects in the image can be obtained using IRAF. Load the STSDAS and GASP packages, then first form the RA/DEC world coordinate system for file image.fits by typing:
makewcs image
Then display the image and measure positions with the image cursor by typing:
display image 1 rimcursor wcs=world wxformat=%12.2H wyformat=%12.2h
Alternatively, if the (x,y) coordinates of the object are known, convert these to RA and DEC by typing:
xy2rd image x y