dsavransky
commented
8 years ago Recovering rm journals for issue:
mperrin: Oddly the POFFSET and QOFFSET keywords don't seem to be set in all cases - e.g. the 131212 dataset for HR4796A has the offsets=0 even for the skies. Does this depend on how the OT skies are set up?
Keywords to check for offset include POFFSET, QOFFSET, RAOFFSET, and DECOFFSE.
mperrin: This seems reasonable to tackle in the next 6 months sometime.
Probably needs some coordination with Fredrik and Pascale to understand what the deal is with the offset keywords.
mperrin: Hi Pascale,
Could you help me understand the FITS header keywords for telescope offsets, so that I can ensure the data parser knows enough to tell the difference between on-target observations and sky frames? Thanks.
phibon: Hi Marshall,
The POFFSET and QOFFSET keywords are the indicators for telescope offsets. We designed the sky observations in the OT with a POFFSET=20 and QOFFSET=0. (You could also use the RAOFFSET and DECOFFSE.) I looked at the 131212 data and the skies for HR4796A were not taken from a OT sequence. But the skies for HD100546 on 131212 were and do have the correct offset values in the header.
Other keyword for which the value changes between the target and sky observations are M2OFFLOAD, CALLOOP, AOCLOOP, WOFLOOP, AOTTLOOP.
mperrin: auto reducer now recognizes and works with skies. data parser too, mostly. Needs a little more work but getting close.
kfollette: OK to close this Marshall?
We should teach the pipeline about sky frames. These can be recognized from the P and Q offset keywords in the headers.
1) GPITV should check these keywords and append "sky" to the displayed object name if you're offset more than an arcsecond or two 2) The data parser should check these keywords, mark the sky frames as a separate sequence from the science target data, and use the sky reduction recipe for them.