Rotating the Detector (UHRF)

• Configure UHRF to the laser.
  UHRF: FETCH 6328_LASER
  UHRF: CONFIG
  UHRF: ARC LASER
  Take 10 second exposure, adjust UT and UG to roughly centre the line on the CCD (see Section ), then switch to a small, unbinned central window ( e.g. THOMSON_CENTRE). Adjust UFC/UFF to bring it into focus. (See Section .)

• The detector must now be rotated to align the laser line with the CCD rows. (This contrasts with UCLES and the RGO spectrographs for which the orders are aligned.) This should not be done with the slit angle; this must be SA 2160 for the slit to lie horizontal through the spectrograph and deliver maximum resolving power. FIGARO expects the line to lie vertically, so once the exposure is taken, issue the FIGARO ROTATE command before ROTATION. ROTATION will cross-correlate the ends of the laser line and calculate the amount of camera rotation required. A 4 mm hex-key is required to loosen the clamp on the CCD mount, and the CCD can be physically rotated to the new micrometer setting. Detector rotation should be better than .05 of a pixel.

• UHRF should now be ready for the observer.