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WFI Contamination Event 19 August 2005

During a warm up of the WFI Dewar during 19 August 2005 the system that controlled the temperature malfunctioned and the Dewar was brought to temperatures in excess of 90 degrees celsius. This contaminated the Dewar window and the CCDs. The system was later decontaminated but it started slow process of re-contamination. Data taken before 19 August 2005 should not be calibrated with data taken after this date, and vice versa. This page was born to keep track of the contamination and to determine the duration/validity of dome and sky flats. As of 20 October 2005 we have seen a change in beta-light frame characteristics of 1.5%/month.

QC1 at WFI

For those of you who would like some additional information, please note the following:

• The bias frames are combined in a master bias frame after overscan subtraction.
• Dome flat field frames are overscan subtracted, then the master bias is subtracted, and the resulting frames are combined.
• Sky flat field frames are overscan subtracted, master bias subtracted, and combined.
• The dome flat is divided by a fiducial dome flat. Statistics are extracted in each of the 4 corners, at the center of each of the 8 chips, and at 4 small regions near the center.
• The skyflats are divided by a fiducial skyflat frame. Statistics are extracted in each of the 4 corners, at the center of each of the 8 chips, and at 4 small regions near the center.
• The statistics are displayed in this page for each of the filters.

Evolution of dome flat fields

Evolution of sky flat field

Latest beta-light ratio contour map.

Time evolution of DOME flat field

• Latest U/50 ratio contour map.
• Latest B/123 ratio contour map.
• Latest V/89 ratio contour map.
• Latest Rc/162 ratio contour map.
• Latest I/203 ratio contour map.
• Whole archive.

  The plot below shows the evolution of the dome flat fields. Each point marks the value of the ratio of the dome flats over a fiducial one. Sixteen areas are ploted: the four corners where the contamination effects are maximal, four areas around the center of the mosaic; and 8 regions one near the centers of each of the chips.

  
  
  

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  Time evolution of SKY flat field

  • Latest U/50 sky ratio contour map.
  • Latest B/123 sky ratio contour map.
  • Latest V/89 sky ratio contour map.
  • Latest Rc/162 sky ratio contour map.
  • Latest I/203 sky ratio contour map.
  • Whole archive.

    The plot below shows the evolution of the SKY FLAT field frames. Each point marks the value of the ratio of the dome flats over a fiducial one. Sixteen areas are ploted: the four corners where the contamination effects are maximal, four areas around the center of the mosaic; and 8 regions one near the centers of each of the chips.

    
    
    

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    Latest beta-light ratio contour map

    The spacing between the contours below is 0.1%

    

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    Send comments to <ls-sciops@eso.org> Last update: Oct 19, 2005

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