Reduce time between observations

[wtgee]

@jamessynge was asking about time between exposures so I did a quick plot and we are definitely too high right now.

Note that this is likely related to #361 regarding why observations are not getting scheduled quite correctly. Often for PAN001 it gets through something like 55/60 exposures and then does meridian flip or ends night. The scheduler doesn't account for the time between exposures so after a while this adds up to a lot of extra time for an observation.