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Catalogs creation explanations

The first part of the RTAS consists in the reduction of the useful information from 700 Mo (the size of one Megacam image) to a few tens Mo. The pipeline automatically checks the presence of a new image as soon as it has been pre-processed by Elixir and starts the following treatment for each CCD:

  • Conversion of FITS image to JPEG format for future display on comparisons web pages, extraction of the FITS header and addition of new entries, like magnitude and mu-max completness.
  • Creation of a catalog of objects using SExtractor; in this catalog are mentioned X and Y position, RA and DEC, magnitude and mu-max, FWHM and a SExtractor flag
  • Astrometric calibration using USNO catalog
  • Sorting of objects according to their astrophysical properties into stars, galaxies, faint objects, saturated objects and cosmic rays

All these results are then summarized in real time on an automatically generated HTML web page described lower and can be viewed by everyone on the Internet.

Single pages explanations

This page displays the list of the QSO observing runs which have been processed by the RTAS.
The dates of the runs can found here.

Clicking on the name of a run shows a new page entitled 'NNXXNN Catalogs', where NNXXNN is the QSO Run ID. This new page shows the list of exposures taken for the Very-Wide survey during this run. There is one exposure per line. Each line contains the following information:

| 742866p 04AL06 2090p013N | 04AQ03 2004-04-27 8:04:21.76 | 13:49:19.00 -09:47:26.0 | 90 g | 0.65 22.53 322 |
  • Exposure number
  • Run ID (see Observing Programs Identificators)
  • Field of view (see the nomenclature)

  • QSO Run ID (see Megacam Calendar)
  • Date of observation
  • Start time of observation (UT)

  • RA of the center of the field
  • DEC of the center of the field

  • Duration of exposure
  • Filter (g,r, or i)

  • Precision of localization with respect to the USNO-1A catalog
  • Magnitude of completion
  • Number of astronomical objects detected per CCD

These last three numbers are average values over the 36 CCDs of one image.

Clicking on a line displays a new page entitled 'xxxxxxp Catalogs Creation and Calibration', where xxxxxx is the exposure number. This page shows the result of the catalog creation phase in three plots. The program makes one catalog per CCD (there are 36 CCDs in one image), and the abcissa of the plots is the CCD number.
The lower left plot shows the number of objects detected (total=astrophysic sources + cosmic rays).
The upper right plot shows the completeness of the catalogs.
The lower right plot shows the quality of the astrometry with respect to the USNO.

Using an interactive script, collaboration members are able to directly validate or not the night process, and so allow the second stage of the processing which involves the comparison of the image with previous images of the same field.