[Issues] MasterFlat missing the overscan correction option

heraud at astro.uni-bonn.de heraud at astro.uni-bonn.de
Sun May 20 14:33:33 CEST 2007

Hi John,

> Hi Philippe,
> It was decided when the overscan correction became a process parameter
> that
> the MasterFlatFrame did not require it.  This is because the
> MasterFlatFrame
> is derived from reduced calibration frames and not raw calibration frames.
yes but these reduced calibration frames (i.e. masterdome and
mastertwilight) depend on the overscan correction which was chosen to make

> As there is no overscan correction to be done, the parameter is
> unnecessary.
So it means you don't care if the masterflat is made of a masterdome and 
a mastertwilight wich were obtained with a different overscan correction?
Of course the bias level is supposed to be negligable compared to the dome
and twilight levels but then what is the point of having an OC for dome,
twilight and masterflat if we don't use it properly?
> Have you seen any overscan-related issues in your MasterFlatFrames?  If
> so, what is the nature of them?
It is simply not consistent as it is now.
If there would be a overscancorrection parameter in the masterflat it
would ensure that it is made from a masterdome and mastertwilight with the
_same_ OC which seems logical.

> Cheers,
> -=John
> On Fri, 18 May 2007, Philippe Heraudeau wrote:
>> Hi All,
>> The MasterFlat recipe misses the overscan correction option,  which
>> means it
>> will pick up the last created master dome and master twilight
>> indpendant of their overscan correction  parameter.
>> This should be updated to  be consistent  with the dome and twilight
>> creation
>> and avoid using the wrong master dome or twilight.
>> Cheers,
>> Philippe
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