RE: Survey Strategy

[Tom Droege <tdroege2@earthlink.net>]

Rob,

Yep, I would wait.  I don't think you will be able to fix it so because 
there will still be slack in the chain drive.  This is what I am looking 
at.  The fix I am planning will get around this.  But it is at least a 
couple of months away.  Essentially, I am designing a big pulley to go on 
the carriage to be driven by the motor somewhat moved from it's present 
position.

Note that once you say "start scan" the transfer to memory goes to 
completion and the Stamp is freed up.  You have an exactly 46 second 
wait.  I can generate the exact time but it is very close to 46 seconds and 
is crystal controlled so it will vary much less than 0.1%.  You can then go 
off and do anything you want, including using the Stamp to do things.  When 
you get around to it, you can start testing for done.

So I think you can do what you want to do:

1) close the shutter
2) start the scan
3) look to see what you want to do next
4) move the telescope to the new position
5) start the RA drive going to get rid of backlash
6) test for the block done
7) note the time and open the shutter to start taking the next image
8) go to 1)

Note that with this sequence, or something like it, one is dead for exactly 
46 seconds between frames.  You should always be able to get ready for the 
next frame in this time.  I do not think that you will be able to see any 
effects from moving motors, etc., in the data, but one should check.

Tom Droege

At 12:51 PM 10/4/02 -0600, you wrote:

>I believe I've signed up for #2 already.  It will be implemented with my
>Perl Controller/Driver though...  Currently, I am working on moving during
>the CCD to memory card transfer.
>
>What is your field upgrade?  Since I have not place my Mark IV outside yet
>(this month I will!), I have not 'fixed' the declination sprocket set screw
>wiggle yet.  Should I wait on that?
>
> > -----Original Message-----
> > From: Tom Droege [mailto:tdroege2@earthlink.net]
> > Sent: October 04, 2002 12:37 PM
> > To: Robert Creager; tass@listserv.wwa.com
> > Subject: Re: Survey Strategy
> >
> > Rob and all,
> >
> > Yes, Arne's scheme looks OK to me and he is the expert.  But the present
> > Mark IVs will not do very well at it because they cannot point accurately
> > in declination.
> >
> > I have been worrying about this myself since I got TOM2 and TOM3 running
> > and see how good the dec. drive is.  It is much worse than I thought.  So
> > something needs to be done.
> >
> > I have been designing a fix that could be put in place in the field.  I
> > think it will work OK and get the pointing down to a few minutes in
> > declination.
> >
> > What will then be needed is software that is capable of doing a program
> > such as described by Arne.  I think the particular sky map used is
> > unimportant.  Probably we should all use the same one.  I think a 4 degree
> > grid is just about right.  We get about 4.2 degrees of field and with a
> > better dec. drive the .2 overlap should be enough.
> >
> > Now that I have looked at a lot of data, I think it is important to point
> > at exactly the same spot for each frame with a different epoch.  The data
> > will not be as consistent if stars move around in position in the
> > frame.  This just hides absolute accuracy, but that is life.  By matching
> > position in frames we will do better in relative accuracy, and that is
> > what
> > is needed to detect variables.
> >
> > OK, gang, here are the projects:
> >
> > 1) Get a field kit out to upgrade the dec. pointing.
> >
> > 2) Get table driven software out that will allow following a program such
> > as that described by Arne in TN 48.
> >
> > I will do 1)
> >
> > Tom Droege
> >
> > At 09:36 PM 10/3/02 -0600, you wrote:
> >
> > >Just looking around in the Tech notes, and ran across
> > >http://www.tass-survey.org/tass/technotes/tn0048.html from Arne.  This
> > >still a good strategy?  Does anyone have a copy of "skymap.txt", as it
> > >doesn't reside on Arne's FTP site any more...
> > >
> > >Thanks,
> > >Rob