[News] Some issues
Dr. Mark Neeser
neeser at usm.uni-muenchen.de
Thu Sep 11 13:55:55 CEST 2003
Hello All,
As a test of data reduction routines (astro-wise vs. Bonn pipeline vs.
IRAF) we have immersed ourselves (primarily Jan Snigula and
Yuliana Goranova) in the astro-wise pipeline using our WFI data.
Here some results/comments:
- Dataset used for testing: WiFI- images taken over 6 nights
(approx. 50GB).
Time for testreduction: approx. 1 week (most of the delays were caused
by unannounced pipeline changes occurring during the reduction.
Details:
- COSMICFILTER:
We tried to implement our cosmic filtering routine (cosmicfits from
Claus Goessl) in the pipeline. This attempt failed, due to the
current handling of bad columns/pixels in the images and the
existance of negative pixel values. The latter problem can be
circumvented in the program call, but the bad columns/pixels would
need to be replaced (PRIOR to executing our cosmic filter routine) with
a well defined NaN value, e.g. 0. Essentially, our cosmic filter
routine treats the bad columns as cosmic rays and spends an inordinate
amount of time trying to detect/correct them. It would be easy to
mask these as NaN's prior to running "cosmicfits".
- BAD COLUMNS:
Bad colums in general must be taken care of at an earlier stage of
the pipeline than currently implemented (see example ps
file). This was already discussed by Mark and Roeland.
- SWARP:
The pipeline currently uses a beta version of Swarp (swarp 2.0b),
that fails to create usable weight images. Reasonable weight
images are essential for obtaining a fast run-time with cosmicfits,
and are crucial when the frames on which cosmic rays are detected
have strong intensity slopes.
- UPDATES:
Unannounced pipeline changes that change object definitions, require
changes to the database, that can be time consuming, given the fact,
that we have to figure out the changes from the code, and guess
the needed Database changes. Usually Danny sends out an e-mail
explaining the required changes (usually after talking with Roeland
about the changes in the pipeline), but these e-mail come about 2
days after the changes, causing severe interruptions.
Suggestion: Create a stable branch of the pipeline in the CVS with
weekly? updates from a development branch, and the changes in these
updates should be discussed with the DBAs before, so that updates to
the pipeline cause as few interruptions as possible.
- TESTS:
- Bias:
Subtracting resulting masterbias from its raw input frames
rawbias file name median stddev average stddev
seWFI.2003-01-05T20C54C42.283_4.fits -0.199997 18.876 -0.244914 18.8759
seWFI.2003-01-05T20C55C44.983_4.fits -0.100006 18.9255 -0.161555 18.9254
seWFI.2003-01-05T20C56C42.354_4.fits 0.100006 18.89 0.00905352 18.8897
seWFI.2003-01-05T20C57C39.851_4.fits 0.100006 18.9164 -0.00907611 18.916
seWFI.2003-01-05T20C58C34.232_4.fits 0 18.8818 -0.0418041 18.8818
seWFI.2003-01-05T20C59C33.157_4.fits 0 18.881 -0.0651421 18.8809
seWFI.2003-01-05T21C00C32.066_4.fits 0 18.8516 -0.0559038 18.8515
seWFI.2003-01-05T21C01C33.362_4.fits 0 18.888 -0.0407198 18.888
seWFI.2003-01-05T21C02C30.338_4.fits 0.100006 18.8894 0.000104276 18.8891
seWFI.2003-01-05T21C03C29.919_4.fits 0.100006 18.9252 0.0489991 18.9252
(Is there a numerical round-off occurring in the median computation?).
- DomeFlat:
Flatfielding biassubtracted raw domeflatframes using the processed
domeflat. ( SEM = std. error)
flatfielded raw flatfield filename median stddev average stddev
dseWFI.2003-01-06T21C59C26.278_4.fits 17778.8 90.3731 17778.1 90.3702
dseWFI.2003-01-06T22C00C53.969_4.fits 19056.3 94.5017 19055.6 94.4991
dseWFI.2003-01-06T22C02C15.050_4.fits 19074.4 94.4472 19073.4 94.4418
- TwilightFlats:
Flatfielding biassubtracted raw twilightflatframes using the processed
twilightflat. ( SEM = std. error)
flatfielded raw flatfield filename median stddev average stddev
dseWFI.2003-01-04T00C17C43.159_4.fits 17885.3 122.664 17886 122.662
dseWFI.2003-01-04T00C19C14.085_4.fits 17161.4 134.724 17161.9 134.723
dseWFI.2003-01-04T00C21C01.056_4.fits 16581.6 151.299 16582.4 151.297
- Astrometry:
From visual inspection of stars from the USNO catalog overplotted
on the image, the astrometric solution determined by the pipeline
seems to be very accurate even out to the edges.
Hard numbers:
mean position differences in arcsec:
RA DEC
-0.0002 0.0001
mean sigma of the position differences in arcsec:
RA DEC
0.4199 0.4021
Cheers,
Mark
=====================================================
Dr. Mark J. Neeser
Institute for Astronomy and Astrophysics, _/ _/ _/ _/_/ _/
Ludwig-Maximilians-Universitaet Muenchen _/ _/ _/_/ _/ _/ _/ _/
_/ _/ _/ _/ _/ _/ _/_/
Scheinerstrasse 1, _/ _/ _/_/ _/ _/
D-81679 Muenchen, Germany
Tel: +49-89-2180-5995
Fax: +49-89-2180-6003
email: neeser at usm.uni-muenchen.de
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