RE: Small adjustment to strategy for TOM1

[Tom Droege <tdroege@veriomail.com>]

Rob and all,

That is the strategy.  The flat field run serves two purposes.  It give a 
once a night measure of a large area.  This can then be used as flat field 
data to reduce both the flat run and the follow run.  The "follow" runs 
give many measurement of the stars in single fields.  The "flat" runs give 
one or two measurements of stars in a larger area.

The idea is to get photometric data on the stars that we measure at all 
time intervals possible.  The "follow runs cover 2.5 hours at roughly 3 
minute spacing.  The "flat" runs get a measurement every night there is a 
run.  Since we cover 30+ degrees, we will get several measurement over the 
month they are in view.  Then next year we get them again and ...

Tom Droege

At 05:24 PM 10/17/01 -0600, you wrote:

>Maybe an odd question, but is there any reason NOT to reduce the images used
>in creating the flatfield?  Buys you extra observations of stars at the
>least.
>
>What if you created your flatfield star exposures by stepping some number of
>pixels in both directions (5, 10 or some small pixel count).  Then you could
>get some repeated measures of a set of stars, while creating good(?)
>flatfield data also.
>
>Or is it better to use 'random', or large offsets for this purpose.
>
>Later,
>Rob
>
> > -----Original Message-----
> > From: Stupendous Man [mailto:richmond@a188-l009.rit.edu]
> > Sent: Wednesday, October 17, 2001 3:18 PM
> > To: tass@listserv.wwa.com
> > Cc: tdroege@veriomail.com
> > Subject: Small adjustment to strategy for TOM1
> >
> >
> >
> >   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
> >
> >