Focusing StanCam - a quick help

1. Stop auto-guiding
2. Start a focus sequence with the command: focusexpose (focus start-value) (focus step-size) (exptime)
   A good first guess is focusexpose 22000 100 15
   The image should look like this:
   

3. Use the sequencer script focus-auto focus-step-size [image] to analyse the image.
   E.g. focus-auto 100

4. You can also use the Postprocess Imexam to measure the FWHM of the images (use a-key), quite imexam by typing q-key
   Take another focus sequence with finer focus step size if needed.

   If you have problems with the BIAS/imexam you can use iraf/imexam at florence.

   • in florence xterm window type xgterm &
   • in xgterm window type ecl and ds9 &
   • display saved stancam image displ /data/stancam/STnnmmxxxxx[1] 1 fi+ where nnmmxxxxx stands for the prefix and the number of the image
     (see the testimage " /data/stancam/EXfocus.fits")
   • type imexam and move the cursor on top of the star and press r for radial profile and/or a or , for aperture photometry
   • quit imexam by pressing q
   Note, that the telescope focus vs FWHM curve is rather broad around the optimum focus.