Small adjustment to strategy for TOM1

[Stupendous Man <richmond@a188-l009.rit.edu>]

  Tom wrote:

> Here is what I am trying to do every night:
> 
> 1) Take a string of exposures covering about 4 x 30 degrees of sky ...
....
> 2) Follow as many fields as possible for as long as possible for the 
> remainder of the night.  I seem to be getting 2 to 3 fields these days on a 
> good night.  I can follow a field for about 2 1/2 hours.  I just pick up 
> whatever field is available when the previous field is completed.
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^

  If you can arrange it so that the 2 or 3 fields you follow each
night are _roughly_ the same (that is, there's an overlap of at
least one degree in RA from night to night to night), then your
dataset will be much stronger than if the "follow" fields are
different on each night.

  One sort of simple way to ensure this is to move to the home position
in RA at 1:00 AM and start a follow run tonight; then, tomorrow night,
move to the home position at 0:56 AM; and the next night, start at 
home position at 0:52 AM, and so on.  The same stars will rise/transit/set
4 minutes earlier each night.

  If you start the first follow field carefully at the right time 
each night, then all the subsequent follow fields will also be
correct (to within the large 4-degree field of the Mark IV, I believe).

  After a month or so, your first "follow" field will have moved
so that it starts at, say, 11:00 PM instead of 1:00 AM, and it
now cuts into the early sequence of frames.  No problem --- drop
that first field, and just start at the right time to pick up
(what used to be) the _second_ "follow" field.  

  Switching the "follow" fields once a month or so will be about
right, if you can follow each field for two hours.  This will also
allow your "flat" fields to move around the sky, too.

                                              Michael