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XMM-Newton Science Analysis System


evproject (attcalc2-1.0) [xmmsas_20050815_1803-6.5.0]

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Projecting the events

The projection direction (ie, the direction of the point at which the projection plane is tangent to the celestial sphere) is user-selectable from the following alternatives, chosen via the parameter tangdirstyle:

• tangdirstyle=nom: task uses the current nominal pointing direction of the s/c, as defined in the RA_NOM etc keywords of the event list;

• tangdirstyle=obj: task uses the pointing direction of the celestial object, as defined in the RA_OBJ etc keywords of the event list

• tangdirstyle=pnt: task uses whatever value was calculated for the RA_PNT etc keywords (see section 3.4);

• tangdirstyle=user: the task reads the RA and dec supplied by the user via parameters tangdirra and tangdirdec.

As said in the introduction, the `pixel size' of the X and Y values is fixed at 0.05 arcsec; the remaining thing to be specified is the maximum allowed X and Y values. This is specified in a somewhat roundabout way via the parameter imagesize, which specifies the total half-width and/or half-height of the projection plane in decimal degrees. After offsetting by imagesize, X and Y can therefore run from 1 to $2 \times$ imagesize $\times 3600 / 0.05$.