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XMM-Newton Science Analysis System


esky2det (esky2det-1.12) [xmmsas_20080701_1801-8.0.0]

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Uncertainties.

If uncertainties are not requested, the uncertainty fields or columns are not included in the output.

Note that a single uncertainty only is provided for DETX/Y output, whereas separate X and Y uncertainties appear for RAWX/Y. There is no particular need for separate RAWX and RAWY uncertainties while the task is restricted to EPIC application, since pixels on the EPIC cameras are square (except for a small number at the PN chip edges), but an extension to RGS would require separate uncertainty values: hence their retention.

It was decided not to allow the user to specify separate RA and Dec uncertainties because the resulting uncertainty ellipse, although orthogonal in the RA/Dec coordinate system, is no longer necessarily so in a camera-centric system. The possible gains were not considered worth the added complication of specifying a rotated ellipse.