OSMOS Long Slit Acquisition Procedure

John Thorstensen (Dartmouth) has developed a pyraf script called osctrtask that is extremely helpful for long slit acquisition. The acquisition process is as follows:

1. Point the telescope to the desired field and acquire a guide star with the JSkyCalc24mGS (also by John Thorstensen).

2. Take two setup exposures: an acquisition image and a slit image (both ideally with an ROI to speed readout). The disperser should not be in the beam for this step. Note that if the ROI is at least 4x1k, the acquisition image should have a sufficient number of stars for the centering task to calculate a WCS solution.

3. ssh to agung, start ds9, type "cd Scripts/" from the obs24m home directory, and type "pyraf" to start pyraf. Confirm that there are no other instances of IRAF or ds9 running on agung.

4. Type:

pyexecute('osctrtask.py')

pyexecute('osqlsp.py')

pyexecute('osbias.py')

and then run osctrtask with the appropriate file names. Note that the entry for (prefix) should end in a '.', e.g. 'os100929.' and that (getwcs) is successful most of the time if the acquisition image is at least 1x4k pixels.

5. The script creates bias-subtracted temporary images called acqimage and slitimage and displays them in frames 1 and 2 in ds9. Mark the slit with an x and the object of interest with an a, then type q to quit.

6. Transcribe the output DX and DY values into xmis

7. Turn off guiding and move the guide probe.

8. Move the telescope (not the guide box) with the hand paddle so that the star is back in the guide box and resume guiding.

Updated: 2010 Sept 29 [pm]