The output file (in either format) directs the plotting package (gaia or ds9) to draw a circle of a certain radius at a certain sky position. The radius can be made an arbitrary function of column values in the input source table. The task first calculates the value of the column expression in parameter radiusexpression. What happens next depends on the value of the radiusstyle parameter. If this is `raw' (the default), the task does no further processing: the result of evaluating radiusexpression is used directly as the radius of the circle to be plotted. However this procedure is clearly somewhat vulnerable to error by the user. One can envisage a situation in which several iterations might be necessary before the sizes of the plotted circles attained a pleasing appearance. This is unavoidable if precise control over the source circle radii is desired; however there may be other occasions on which the user just wants the source circle radii to display qualitative information. It is for this purpose that the other setting, `auto', of radiusstyle was designed. Under this setting, slconv does its best to scale the circle radii already evaluated from radiusexpression such that the maximum and minimum radii will be sensible fractions of the image size, and so that the circles are distributed fairly evenly between these extrema.
XMM-Newton SOC -- 2021-11-30