RE: Disk Set 20: dates and times

[<aah@nofs.navy.mil>]

Mike asked:
>...I noticed that Tom is storing the time of exposure start
>while Michael is storing the tie of mid exposure.  Which should we be using?
>Which is more common amongst professionals?
  Most common is start of exposure, especially for the UT keyword.
Some systems have added UTSTART and UTEND, but these are less common.
Programs like iraf automatically create final times using
UT and EXPLEN to give midpoint values.
Arne