PNS MANUAL: Taking Twilight Spectra

For purpose of calibration, it is useful to take sky spectra all over the field, using the mask. This is useful for mapping filter profile over the field, and for checking the velocity calibration using the sky absorption lines.

The procedure is as follows, to be executed with telescope pointing at blank, bright sky:

  1. on PNS console, insert the mask: MASKC and close shutter: SHUTC.
  2. on DAS, prepare expose time "sky spectrum" (try 60sec exposures at 30min after sunset).
  3. on PNS, open shutter: SHUTO
  4. before CCDs start to read, close shutter: SHUTC
  5. let CCDs read out.
Note that the PNS command EXPOSE cannot be used, as it moves the mask out!
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