Big dither: only the primary guide dither is passed from ORViewer

[jeanconn]

This one is a bit in the weeds but:

For an HRC observation, detector nominal dither is 20x20.

For obsid 20168 , a big-dither HRC observation with 64x8 dither, ORViewer calls proseco with 64x8 dither to check for imposters and bad pixels near guide stars. However, dither reverts to 20x20 for the last 5 minutes of the observation. This means that there are pixels in the region of z dither that are not checked (20 - 8) by proseco.

I think it would be wise to check that pixel region in starcheck now, and to eventually set ORViewer to use the max dither in each axis if there are multiple dither amplitudes in the observation (obsid 20168 should really use guide dither 64x20). For ACIS "nominal" big dither observations this isn't an issue (8x64 -> 8x8).

[jeanconn]

Seems like we might want to add a hack on this for aca_preview, just to avoid the case where the star is too close to the dither-padded edge in the axis that goes from 8 to 20 at the end.