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: http://xmm.vilspa.esa.es/calibration/documentation/CALHB/node912.html
Дата изменения: Tue Sep 20 19:45:21 2011 Дата индексирования: Mon Apr 11 03:36:29 2016 Кодировка: Поисковые слова: 2df survey |
The new distortion map was generated from in-flight observations of the G153 field. The U filter was used and the positions of 813 stars were measured. The old map was based on a LMC field with only 230 sources. Since the main source of distortion is the detector fiber taper, this map is applied to all filters, including two OM grisms. The platescale is a natural by-product of this analysis. In orbit the platescale was found to be 0.4765 arcsec/subpixel for the V-filter.
The distortion map for the grisms, which describes the displacement of the zero orders in the grism image with respect to the direct image was measured in the same way. Observations of the Sco X-1 field in revs. 402 and 688 using the V filter and both grisms have been used to measure the positions of the sources and their respective zero orders. Then a map has been computed following the same method described for the geometric distortion.