Monday, October 31, 2011

Night Log 2011-10-30

SA: Tim
SO: Siphelo


clouds came over at the end of twilight and then high humidity shut us down for good at 21:30.

used the closed-dome time to determine simpler guidelines for doing QTH flats. it turns out to be very straightforward:

- for the PG0300, PG0900, PG1300, and PG1800 gratings the QTH2 lamp (the one on the right on SOMMI) with the clear-uv filter works best at all wavelengths. with the 1.5" slit and 2x2 binning there were enough counts with 1 second exposures in all cases except the blue-most settings in PG1800 where 3-5 seconds would be better. other slits scale accordingly.

- for PG2300 the clear-uv filter with both QTH lamps turned on works the best. 1 sec sufficient with 1.5". 3-5 seconds probably better in the blue.

- for PG3000 it appears that QTH1+QTH2 plus the red-clear filter works best in the blue (station <=110) as well as the red (station >120). best exposure is 5 seconds with 1.5" slit. in between QTH1 with clear-blocked works the best with 3 second exposures. there is some kind of emission line or ghosting that goes away when QTH2 is turned off (see P72-74). need to look into that more closely.

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