GMOS data reduction notes

Spectroscopy

Some URLs for other peoples advice:

For imaging - could only find old flats in the archive. Anyway, procedure:

gprepare the raw data files (not the processed flats)
gireduce them using trimming, no bias (but overscan), and the right flat
gmosaic them
imcombine with no offsets and eg. median - then smooth this with big median filter (suggest larger in Y than X to try to avoid the chip gap becoming an issue) to make a delta-flat, just for large scale. Divide all images by this delta-flat. [NB this step might be best achieved using smartflat on some occasions, then median smoothing the output of that]
imcombine with offset=world

Put all frames in directory raw
gemini.gmos
run gprepare with fl_addm=yes
run gsflat with subtraction of overscan rather than bias (I would suggest -- unless you have bias)
From here I generally follow the steps in file:///Users/nrt1/Desktop/SoftwareStuff/GMOS_reduction/gemini_reduction.html
NB. I have put the sensitivity functions from reduction of standard star data in a directory on my desktop GMOS_specphot.
NB2. recommend at least skysub and extract be done with an element of interactivity (e.g. defining range for sky, order of fit etc.)
TIP: use skysub region fairly close to the trace of interest, not whole chip!
Perhaps see GRB 121128A, for quite a good job by me.