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: http://xmm.vilspa.esa.es/sas/5.4.1/doc/omfchain/node14.html
Дата изменения: Fri Jan 10 23:33:22 2003 Дата индексирования: Sat Dec 22 10:29:24 2007 Кодировка: Поисковые слова: reflection nebula |
The absolute level of the resulting light curve is dependent on the precision of the current PSF. Relative variations between time bins may also be introduced due to migration of the source centroid within the window when part of the source is beyond the window boundary. It is not possible to fully correct for tracking drift, even when tracking history is available, when the source is near the edge. It is generally advisable to adopt a fixed extraction radius (not less than 6 full-resolution pixels) for a given set of fast mode exposures. This is currently used as the default value for the chain, enhancing S/N for weaker sources.
One may change this parameter by using the command `omfchain srcradius=...'. If srcradius is set to a negative value, it will be fixed while processing all the exposures (this is the default action of omfchain). If changing srcradius parameter one should also remember that the radii of the background annulus scale with it according to the bkginner and bkgouter parameters (see description of these parameters).
implot set= sky_image_file.FIT withsrclistset=y srclistset=osw_source_list_file.FIT device=your_device (e.g. /XW) itv=1 radius=3 maxsrc=10 colour=7.
While often there will be only one object in the image, one should check for spurious detections which could affect the analysis of the target source and also for missed sources or prominent objects in the window, which may contaminate the target. It is possible to change the detection efficiency via the boxscale, smoothsize, nsigma, and contrast parameters (see the description of omdetect.