Create a clone of the chart, draw into it markers and star ids for all
the blobs used for estimating magnitude, and redisplay it. Uses the list
of open images to find the ImFrame containing the chart. If the chart
parameter is null it still uses the list of open ImFrames to try to find
one which has a StarChart and that chart has stars with the same ids as
the measured blobs. If no such chart can be found just give up quietly
but put a message in the log.
accurate - tells whether the MagnitudeGraph was constructed using
the accurate brightness measurements (rather than cruder measurements
of the blobs as initially detected).