[News] sub window statistics

[Roberto Silvotti]

Hi Oliver,

> Hi!
>
>> From the previous mails I think that somebody are concerned that smaller 
>
> subwindows lead to poor statistics in the case of science frames when 
> stars are laying in this fields. To avoid stars in whatever sized 
> subwindow you can compute the mode of the subwindow/ccd which gives 
> you the "mean" value of the background which only is important to 
> characterize the image. 

This is not the goal in our case.
Just to clarify: we are speaking about BIAS, FF and fringing patterns, 
NOT scientific images.

> We are doing this in Bonn in our pipeline. For this case the mode 
> can't be determined  by only doing some straight statistics, you have 
> to do some fitting which costs time. So a  smaller number of windows, 
> e.g. 9 or 16 would be sufficient.
>
> Cheers,
>     Oliver

Before deciding what should be the best dimensions of the subwindows we 
should consider what are the goals of the subwindow statistics in AWE; 
these goals are described in the manual (section 23.2).
I suggest to look carefully to this description (and may be to do some 
testing) before proposing to change something.
We did some testing and the dimensions we  proposed seem reasonable at 
least for WFI images (but of course everything can be improved). For 
sure we will have to re-test and optimize everything as soon as we will 
have the first OmegaCAM data.

Cheers,
Roberto

 
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         Dr. Roberto Silvotti
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INAF (Istituto Nazionale di AstroFisica)
Osservatorio Astronomico di Capodimonte
via Moiariello 16, I-80131 Napoli, Italy
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tel/fax:  +39-081-5575583/456710
e-mail:   silvotti at na.astro.it
web:    http://www.na.astro.it/~silvotti
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