Incorporating files with differing exposure times in a final image

[kslong]

The procedure that decides what files to Swarp allows for the fact that we mostly had a short exposure with one time and long exposure for another time, and tries to construct images from given filter with fixed exposure times; this made it easy to identify what images to combine.

But this does not allow for the fact that there are cases where the "long" exposure was different fields. If one wants to combine data from different fields this leads to issues in constructing the long exposure image that need to be addressed

[kslong]

Dealing with this issue should be done in SwarpSetup. The create_swarp command is already setup to combine multiple exposure times, and is called from create_commands_from one tile. In this routine, we first call a routine to create a table that contains the number of unique exposure times for each exposure, so we just need a clean way to handle the problems. A "kluge" would to intercept the process at this point, presumably by defining limits on exposure time to put into a long and short exposure

This appears to be the distribution of exposures per filter

      N662   30.0  66
      N662  401.0   1
      N662  473.9   1
      N662  590.7   1
      N662  800.0 118
      N673   60.0 207
      N673  400.0  99
      N673  800.0 181
         r    8.0 205
         r   10.0   6
         r   30.0 104
         r   60.0 190

or if you limit to images with 1.4 arcsec or better seeing

      N662   30.0  32
      N662  473.9   1
      N662  800.0  68
      N673   60.0 184
      N673  400.0  97
      N673  800.0 147
         r    8.0 178
         r   10.0   2
         r   30.0 104
         r   60.0 151

For the purposes of combining images, I assume this means

Long N662 - 800 seconds only
Long SII - 400 and 800 seconds
Long r - 30 - 60 seconds

For short exposures - I assume we wnat

N662 30 seconds
N673 60 seconds
r 8 and 10 seconds.

Note that there appears to be a paucity of short N662 exposure with good seeing.

@SeanPoints Please comment on this. I assume you would like to ignore the odd ball exposures.

[kslong]

This should be complete with the latest merge into dev. But I will leave this open until @SeanPoints confirms everything is working properly.