Posted: Fri Oct 21, 2005 4:35 pm Post subject: Question about spectra reduction
I am Paola Rodriguez Hidalgo, a graduate student from UF. I am
experimenting problems when using the task "apall" to extract spectra
from 2D images. Sometimes a weird "bump" shows up in the spectra. It
happens sort of randomly, although I have the suspicion that it might be
related to a hot pixel you can see in the 3 images at physical=
(2048,280) or image=(1549,102). However, we cannot explain how a single
point created such a huge and wide bump. Unexpected bumps have actually
shown up in other spectra too.
I am sending you:
- 3 different spectra extracted from 3 different images
- the 3 images (fBb,0041,fBb,0042,fBb,0043)
- a text file with the parameters I used by default when running "apall"
- other 2 spectra extracted with different parameters (see below)
The data was taking on September 29th with the GoldCam at the 2.1 m
telescope (Kitt Peak).
(Since I was running "apall" interactively, the final images had a trace
order of 7, instead of 4.)
We had set the parameter "clean" off because, for previous experience in
our group, clean on has created changes in the continuum flux or troughs
in the spectrum. Just for this spectrum we have tried with clean=yes or
setting the saturation to a number lower than the value of the hot
pixel. Both have removed the bump (see apredo42b.0001 for the clean=yes
and apredo42.0001 for saturation=6500). Still, we would like to
understand the problem and be sure that this hot pixel is really the
responsible of this bumps before attacking the problem.
Thank you very much,
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