[Comm2011] archival OmegaCAM detector data?

[Gijs Verdoes Kleijn]

Dear Dietrich and Ewout,

In a raw domeflat frame on chip ESO_CCD_#66 I found a saturated column
at columnnumber 276.
Hope this is what you are in need of.

Ewout can retrieve all information regarding this observation using:
http://dbview.astro-wise.org/DbView?mode=object_view&class_str=RawDomeFlatFrame&object_id=f542f1b80228eee2e0307d814c063747

For convenience I have put the fits frame also on-line as:
http://www.astro.rug.nl/~verdoes/OmegaCAM/OCAM.2005-04-13T09:41:54.629_2.fits

Best wishes, Gijs

Dietrich Baade wrote:
> Hi Gijs, John,
>
> we have run into some apparent problem with the OmegaCAM science 
> mosaic, and Konrad amd Ewout suggested that I contact you.
>
> *What we see*
> Bright stars saturate well below 2^16-1 ADU.  Often, this happens at 
> 57,000 ADUs; only the brightest stars reach 62,500 ADU.  The cores of 
> such images have a flat plateau.  This is true for all CCDs (quite a 
> few) in the mosaic that I've checked. 
>
> *What else we know*
> The CCD test reports from e2v show full-well capacities of between 
> 220,000 and 340,000 e-/pixel.  You have previously determined gains of 
> 2.2-2.4 e-/ADU.  A quick on-line estimate here suggests ~2, which I 
> consider consistent.  A gain of 2.3 e- would imply 150,000 e- @ 65,535 
> ADUs, well below physical full well.  FORS2 CCDs from the same batch 
> have a gain of 2.4 and don't run into physical saturation before the 
> limit of the A/D converter is reached.
>
> *What we suspect*
> The numbers for OmegaCAM do not match.  Since the entire science 
> mosaic seems affected, the problem must be basic.  It could be a wrong 
> gain setting by S/W or H/W or similar.  Olaf had no time yet to look 
> into this. 
>
> *What could help us
> *It would be great if you could search your archive for images* 
> *containing saturated pixels with a value of 65535 (=2^16-1).  Don't 
> send us such images.  It will be sufficient if you could provide a 
> brief description.  Ideal would it be if you found a CCD with a 
> (partial) hot column.  In that case, give as us the location or name 
> of the chip and the column number.  The faulty CCD that was replaced 
> in 2009 might also have shown such saturated columns. 
>
> If you do not find anything quickly, suspend your work and let us know 
> how you've proceeded.  We would, then, tell you whether it makes sense 
> to continue.  
>
> Many thanks in advance for your help. 
> *
> *Best regards,
>
> Dietrich.  *
> *
> -- 
> Dietrich Baade    
> ESO - European Organisation for Astronomical Research in the Southern Hemisphere
> Karl-Schwarzschild-Strasse 2,  85748 Garching bei Muenchen,  Germany 
> Email: dbaade at eso.org    Tel: +49 89 3200-6388    Fax: +49 89 3202362 
>   

-- 
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|dr Gijs Verdoes Kleijn         |   astronomer                     |
|e-mail: verdoes at astro.rug.nl   |   OmegaCEN / Kapteyn Institute / |
|www: www.astro.rug.nl/~verdoes |   Target                         |
|tel: +31-50-3638326            |   University of Groningen        |
|mobile: +31-654658050          |   postal address:                |
|                               |   Kapteyn Astronomical Institute |
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