[News] sub window statistics

[Roberto Silvotti]

Hi Ewout,

> Dear all,
>
> We would like to finalize the procedure for deriving and storing 
> statistics in
> subwindows for the images, and it turns out we're still somewhat 
> unsure whether the
> current approach is in fact the best way to do things.
>
> Currently the SubWinStat situation is that for each CCD statistics are 
> calculated
> for:
>
> A) 32 subwindows covering the entire CCD. The windows are 500x500 
> pixels in size.
>
> Our worry is that with this subwindow size, large scale (flat-field) 
> effects and
> stars may be a factor within the subwindows. 

Could you make an example of the possible problems that you mention ?

> Additionally when the idea is to
> characterize the CCD images by a reduced number of numbers, 32
> subwindows may be counter productive, complicating things rather than 
> simplifying
> them.

the computing time and the number of data to be stored seem irrilevant ...

> We could use smaller and fewer windows, for example:
>
> B) 8 subwindows NOT covering the entire CCD. Windows are 50x50 pixels 
> in size.

Yes but then you would not cover the entire CCD and would not 
necessarily detect possible problems.
Moreover how would you decide which are the positions of the subwindows?
Random positions ? Or in some critical parts of the CCD like corners ?

> What are your ideas on this?
>
> Regards,
> Ewout

Regards,
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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