The task evselect creates a simple output image file in the following way:
evselect table=inevlist.fits xcolumn=X ycolumn=Y imagebinning=binSize \
ximagebinsize=100 yimagebinsize=100 \
withimageset=true imageset=image.fits
where table specifies the input event list, x/ycolumn the
coordinates used for the image (here sky coordinates), imagebinning is
a switch for an automatic or user defined binsize, x/yimagebinsize is the
user defined bin size of the image in each direction, withimageset is the
switch to create an image and imageset defines the name of the output
image file. In this example the bin size is set to 100 which corresponds in the
sky pixel system (units are 0.05 arcsec) to 5 arcsec.