RE: TASS database vs. other databases

[Thomas Droege <tdroege2@earthlink.net>]

Others can reply to this better than I but I have been looking at the data.


We seem to get positions to 1 arc second sigma.  This is a problem since
many of the old famous variable stars are out of position.  

Looking at the pipeline documentation at:

http://spiff.rit.edu/tass/pipeline/pipeline-latest/pipeline.html

I am reminded that we use separate catalogs for the astrometric and
photometric steps.  We use a big tycho2 set for the astrometry, and it
seems to be pretty good.  A look at  
http://www.astro.ku.dk/~cf/CD/docs/guide.pdf  found a number in the 2-300
mas range for position accuracy.  So this is much better than the 1 arc
second we see from the big pixels.  

As to matching positions, if you enter a tass position into VizieR, one
usually gets the star that is expected.  Patrick Wills has done this for a
lot of tass stars and this is available on the tass Wiki.  

So the real answer to your question is that it has not been done for all
the stars in the tass data base.  We think the position is pretty good so
when compared to a data set which also has good position then you will get
a lot of matches at the 1 arc second level.  Early on we decided that we
would not try to give tass stars separate catalog numbers since there were
already enough catalogs.  So we just mark them with position.  

I think a lot of work has already been done matching IRAS to tass stars and
I think this was not a problem.  At least no one complained that it was
hard.  ;^)

Tom Droege


> [Original Message]
> From: Robert J. Bradbury <bradbury@aeiveos.com>
> To: TASS <tass@listserv.wwa.com>
> Date: 8/24/2004 4:25:21 PM
> Subject: TASS database vs. other databases
>
>
> Ok, at the risk of asking some more stupid questions
> (yes Tom I'm aware of your "if you aren't clever enough
> to figure this out you shouldn't be here policy -- and
> do appreciate the time you have taken to respond to my
> queries to date... :-;)
>
> I've already posted some offlist comments to Michael with
> respect to problems getting at the archived data and
> performing analysis on it.  (I consider myself reasonably
> clever and getting at the data does not seem (at first glance)
> to be a climb up a rocky mountainside much less a walk in the
> park at this time... :-().
>
> One of the questions that comes up from what I've read
> thus far is the extent to which TASS stars are matched
> to those in other catalogs.  I seem to see that there
> is at least some matching to the GCVS (which I'm aware
> of) and the NSV (which I'm unaware of).
>
> But to what extent are *all* (most?) of the stars identified
> in the TASS images precisely matched to other (earlier)
> surveys (e.g. Hipparcos, Tycho, Palomar, etc.)?
>
> This would appear to be a critical requirement if one
> is going to begin to match things to IRAS data (which
> from my perspective may be essential).
>
> Thanks,
> Robert
>
>