N.B. The new PNS controller software has a bug:
Everytime we press the OPEN button for the uniblitz we actually CLOSE it. And viceversa. Also the log on the control software is misleading. So, the CLOSE and OPEN buttons have the opposite meaning: CLOSE actually means OPEN THE UNIBLITZ... and OPEN means CLOSE THE UNIBLITZ.
Moreover, every time we EXPOSE on the PNS control software, the comand OPENS the shutter and CLOSES the uniblitz (even if in the log it is written that it has opened it). Every time that the exposure is completed.... the comand CLOSES the shutter and OPENS the uniblitz (even if in the log it is written that it has it).

PNS MANUAL: Taking Twilight Exposures

Twilight sky exposures are best taken as if they were science exposures, i.e. controlling the exposure duration with the shutter even though it is a little slow. The alternative, of leaving the shutter open and reading out the CCD introduces far greater nonuniformities as the readout takes longer than the shutter motions.

So twilight sky exposures should be taken in the same manner as regular science exposures.

Sky flats are now handled by the DAS script with the alias "skys"; like "expose" this allows time for the PNS shutter to open and close but gives the images the correct OBSTYPE. PNS Left and PNS Right sky flats

  1. At the DAS enter skys t "SKY"
  2. After the CCDs start integrating, at the PNS Laptop enter: expose t
where t is exposure time.

PNS Halpha arm sky flats:

  1. PNS Laptop: SHUTTER OPEN
  2. PNS Laptop: close the uniblitz shutter (i.e. Halpha arm shutter)
  3. At the DAS enter run pnsHa t+10 "SKY"
  4. After the CCD starts integrating open the uniblitz shutter on the PNS Laptop
  5. PNS Laptop: wait for t seconds and close the uniblitz shutter on the PNS Laptop
where t is exposure time.

PNS Left and PNS Right sky flats simultaneously at PNS Halpha arm sky flats:

  1. At the DAS enter skys_all t "SKY"
  2. After the CCDs start integrating, at the PNS Laptop enter: expose t
  3. PNS Laptop: open the uniblitz shutter if not already open
where t is exposure time.
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