Re: brief note on astrometry/ Which catalog to use.

[Chris Albertson <calbertson@logicon.com>]

Tom Droege wrote:
> 

> OK, I am out of my area of experteze here, but it seems to me that we can
> either:
> 
> 1) Check each measurement of a star as it is made for the possibility that
> it is close to another star by using some higher resolution catalog.
> 
> 2) Wait to check until we have accumulated many measurements on a star, and
> it has popped up on a cut list as a possible variable.
> 
> Seems like 1) should be better if it does not take too much time.

I think you only need to do this check once for each star in the "higher
resolution catalog".  You go through the catalog and for each star
compute the distance to its nearest neighbor and store that back in the
catalog.  Now as you process YASS data and match each observation to the
catalog the check is already done so you have no additional work.
So yes, I think #1 is better and it can take zero time after you pay a
small up front cost.

My question is, "Which higher resolution catalog?"  Is ther a good one
to use?

-- 
  Chris Albertson

  calbertson@logicon.com                  Voice: 626-351-0089  x17
  Logicon, Pasadena California            Fax:   626-351-0699