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:
Note that the PNS command EXPOSE cannot be used, as it
moves the mask out!
- on PNS console, insert the mask: MASKC and close shutter: SHUTC.
- on DAS, prepare expose time "sky spectrum"
(try 60sec exposures at 30min after sunset).
- on PNS, open shutter: SHUTO
- before CCDs start to read, close shutter: SHUTC
- let CCDs read out.
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Last updated 19-07-2001
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