Re: Tycho-2 catalog

[Tom Droege <tdroege2@earthlink.net>]

OK, here is the first one on my list:

RA 81.853
Dec. -0.486
refcat I mag 10.03
tass I mag  7.99
refcat V mag 10.957

This star is in the refcat that I am using.  This is selected from 
big_refcat.dat.  The only thing that I do is sort out the Dec. range I am 
covering to produce the tyc2_photom.dat to reduce the search time.  I 
suspect that we need a better algorithm for generating the I entries in 
big_refcat.dat.  I also suspect that some of the V entries should be 
eliminated.

I found an error in my program which I do not think affected this 
measurement so I am re-running everything.

I had no luck looking this up in Vizier.  Somehow I have messed up what 
catalogs are used and I found nothing.  I guess I need to spend a day 
fussing with Vizier.

I am not saying that the tyco2 data is wrong, only that we may need to have 
a better selection process for generating the refcat that we use.

Tom Droege

At 09:29 AM 1/27/03 -0700, you wrote:
>I agree with Michael R.  As long as the Tycho2 stars that
>are being used have magnitudes brighter than V=10 or so,
>they are consistently accurate and never more than 0.05mag
>off in my experience (except for variables and the oddball
>very red star).  If you are seeing 1-2mag errors, then my
>guess is that you are matching to the wrong Tycho2 star.
>Arne