The task converts sky positions, each specified by an RA/dec pair, to camera-centric coordinates. For the output coordinate system, the user has a choice between DETX/Y or RAWX/Y coordinates. If the latter is specified, the task also calculates and writes the relevant CCDNR. If positional uncertainties are provided by the user, these are also translated into the output coordinate system.
The DETX/Y focal-plane coordinates are the same system as the CAMCOORD2 system described in the cal documentation, except that the units of DETX/Y are 0.05 arcseconds rather than the millimetres of CAMCOORD2. RAWX/Y coordinates correspond to the PIXCOORD1 system and thus have units of CCD pixels. The position in this system depends on the readout node, which is specifiable via the parameter mosccdnode. (Note that this parameter is ignored if the instrument is PN, since its CCDs only have the one readout node.) The default setting mosccdnode=`primary' reflects the fact that nearly all the XMM EPIC MOS data has been taken with that node setting.
The source positions may either be specified one at a time on the command line (ie, 1 source per invocation of esky2det) or in bulk via a FITS file. These two formats are described in more detail below.