XMM-Newton Science Analysis System
backscale (backscale-1.3.2) [xmmsas_20050815_1803-6.5.0]
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To improve the execution time of the task the source region is divided into
a grid which is used to check whether pixels lie on a CCD.
The width of each grid element is set to be 10 detector pixels ( arcseconds) for small regions (region half-width less than 2 arcminutes)
and 20 detector pixels ( arcsecond) for larger regions. It has
been chosen like this to give good coverage of CCD gaps where they make a
significant contribution to the total area while keeping reasonable
execution times for larger areas.
This results in an execution time of 1 minute for a
circular source region of 1 arcminute radius and 5 minutes for
a circle of radius 5 arcminutes.
XMM-Newton SOC/SSC -- 2005-08-16