The user can supply the position, brightness and label of a source. The position can be specified in either of two styles, controlled via the parameter positionstyle: if positionstyle=`radec' (the default), the source J2000 right ascension and declination can be entered (in decimal degrees) via the parameters ra and dec; if positionstyle=`wrtatt', the source position with respect to the spacecraft pointing direction, in the cartesian dispersion/cross-dispersion basis, can be entered via the parameters deltadisp and deltaxdsp. The units of the latter two are arcminutes.
The estimated brightness in counts per second can be entered via the parameter rate; the user source label via label.
More than one user source can be added to the RGS list by running rgssources several times in `modify' mode on the same RGS set, with addusersource=yes each time. Note that a different value of label must be chosen each time, in fact label must be different to any of the values in column LABEL of the old list.
Note that all LABEL values are converted to upper case, hence a source with label given as `Fred' will conflict with a previous source supplied with label=`fred' since they each get translated to `FRED'.
