Subject: Grim H & K spectroscopy

From: Marianne Takamiya

Submitted: Wed, 14 Aug 1996 12:40:33 -0500

Message number: 27 (previous: 26, next: 28 up: Index)

Last Friday (Aug 9), we attempted to observe H and K spectra
(in f/10) of nearby galaxies.  While moving the galaxie's core
across the slit, we noticed that the response in both quadrants
between columns 129-256 is noticeably lower than in the other
quadrants (columns 1-128), at the level that we could no longer see 
the sky-subtracted spectra of the galaxy at all. (When the
galaxy was centered somehwere between columns 1-128, we could distinguish 
its spectra almost clearly.) 
We checked that the core of the galaxy was centered on the slit, 
that it wasn't cloudy, and that we were getting sky-lines. All of
which checked out ok. 
Has anyone noticed this drop in the detector's response before?  
Could this be due to the instability of the bias level? 


Also, we got all worried about the saturation level at 4 in the morning.
The soft-saturation level is quoted to be ~28,000 counts. In what
format? Iraf or Fits?
(The issue here is that the iraf images have a bias level of +8,000 counts,
whereas the fits images that are *later* read with iraf, have bias
levels of -2,000 counts.)


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