[Comm2011] light leaking in through aux filters

[Edwin A. Valentyn]

yes, illumination coorection u  is huge and poorly understood

On 6-8-2011 11:16, Konrad Kuijken wrote:
> I guess it is only apparent when you cover the aux CCDs, something we had not done before. But the effect is pretty unambiguous.
> One prediction is a gigantic 'illumination correction ' in u - has anyone seen that?
> Off to bed 'early' today - Gert graciously granted me a few hours extra sleep tonight! Thanks!
> Koen
>
>
> On Aug 6, 2011, at 11:12, Edwin A. Valentyn wrote:
>
>> Thanks Koen,
>> but why didn't we spot this on the flats taken earlier???
>> Edwin
>>
>>
>> On 6-8-2011 9:40, Konrad Kuijken wrote:
>>> Here are some pictures of the results of Bernards tests covering one of the aux filters in dome flats. Clearly some light does leak through in this way. With the dome lamps the peak contamination of the flat fields are are
>>>
>>> u ~ 30%
>>> v ~ 5%   (Stroemgren)
>>> z ~ 1.2%
>>> r ~ 0.2%
>>>
>>> They affect at least the two ccds near the aux ccds.
>>>
>>> r106, r107, r107-106: r filter from night 217   (ie FLAT217_0106 etc)
>>> u01,u02, u02-01: u filter from night 214
>>> v29,v30,v30-29: v stroemgren from night 216
>>> z27,z28,z28-27: z from night 216
>>>
>>> Notice also how in a few cases dust specs on the filters came and went: they cause a<0.05% effect.
>>> Certainly for u this is going to make data reduction even more complex.
>>> Koen
>>>
>>> <Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg><Mail Attachment.jpeg>
>>>
>>>
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>>>
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>> Prof. Dr. Edwin A. Valentijn       University of Groningen
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-- 
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Prof. Dr. Edwin A. Valentijn       University of Groningen
Coordinator Target                 www   : www.rug.nl/target
Head OmegaCEN                      www   : www.astro.rug.nl/omegacen
Kapteyn Astronomical Institute     tel   : +31 (0)50 3634011/4036 (secr)
P.O.Box 800                        mobile: +31 (0)6 48276416
NL-9700 AV Groningen               e-mail: valentyn at astro.rug.nl
The Netherlands                    www   : www.astro.rug.nl/~valentyn
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