[News] Some issues

[Dr. Mark Neeser]

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