Making DEIMOS Guider Images from the DSS

The lastest revision of DSIMULATOR (Rev. 0b) prints out the coordinates of the center of the guider field. These can be used to create a finding chart as follows(*):

(1) Go to and retrieve a Second Generation Red FITS image at the given coordinates. A box 5 arcmin square should be adequate.

(2) In IRAF, execute the following, where angle = (91.4 - Mask_PA)

> imlintran  dss_im  tv_im  angle angle  0.203 0.203 ncol=1024 nline=1024

(3) This produces an image in the correct orientation for the DEIMOS guider. However, the guider coordinates start in the upper left coordinates, so if you want the y-coordinates to agree you should flip the image in Y:

> imcopy  tv_im[*,-*]  tv_im2    # (input and output names can be the same)

You can then display this image with ximtool or ds9, reverse the Y display (top for bottom), and you'll see the correct orientation and y-pixel values. NB: The xy-coordinates in these images will only agree to within a few pixels of those in the guider image when masks are correctly aligned, as the guider has some distortion. Use the plots or printed coordinates from DSIMULATOR for more accurate expected positions of guide stars.

(*) The next release of the DEIMOS package will contain a small script, DSS_CHART, which will do the IRAF above operations in one step.

Last modified: 27sep2002

Andrew C. Phillips / Lick Observatory