[News] Some issues
Luiz DaCosta
ldacosta at eso.org
Tue Nov 11 16:24:12 CET 2003
Hi
As I mentioned I would also like to be kept informed on these tests
we are right now cross-checking EIS vs Bonn reductions and it would
be nice to add others
Luiz
Roberto Silvotti wrote:
>Dear Mark,
>
>As we are planning to compare the AW pipeline results on the
>Capodimonte Deep Field WFI data obtained by Philippe Héraudeau
>with the results that we obtained here with IRAF,
>I would like to ask you a few more details on your tests on AW
>pipeline vs. Bonn pipeline vs. IRAF, in order to better understand
>what you did in Munich and use at best all these tests during our
>future discussions next week in Groningen.
>
>
>
>
>>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?).
>>
>>
>
>I suppose that the master was calculated with the AW pipeline.
>But it is not clear to me what these numbers tell us: just that each raw
>frame
>has a median or average very similar to the master ?
>
>
>
>> - 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
>>
>>
>
>Here again I do not see what these numbers tell us.
>The stddev are relatively small but, for example, we are not able
>to say anything about flatness.
>
>
>
>> - 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
>>
>>
>
>For what concerns astrometry, the mean differences very close to zero
>tell us
>that there are no offsets in the RA and DEC.
>It is less clear the meaning of the mean sigmas:
>0.4 arcsec is an accuracy of the same order of the USNO catalogue
>(~0.3).
>So this values are normal if they represent absolute accuracy.
>But they would be not good enough for our purposes if they represent the
>relative
>accuracy, for example the difference between one dithering and another.
>So it would be interesting to known exactely what are these numbers.
>
>
>
>Thanks in advance, cheers,
>
>Roberto
>
>----------------------------------------
> Dr. Roberto Silvotti
>----------------------------------------
>INAF (Istituto Nazionale di AstroFisica)
>Osservatorio Astronomico di Capodimonte
>via Moiariello 16, I-80131 Napoli, Italy
>----------------------------------------
>tel/fax: +39-081-5575583/456710
>e-mail: silvotti at na.astro.it
>web: http://www.na.astro.it/~silvotti
>----------------------------------------
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