The following may or may not work as it depends on the data source options specified for your chart. If each point on your chart is represented by a single value in a single record of your found set, you can set up a calculation for the X-Axis values that are blank most of the time, thus "thinning out" the labels shown along the bottom of your chart.
If ( Not Mod ( Get ( RecordNumber ) ; 50 ) ; MergeTest::TimeAndDate )
Will only show a value for every 50th record in your found set.
Thanks Phil, I see what your suggesting, good idea, I'll have a play. Thanks