Re: Tycho-2 catalog

[Arne Henden <aah@nofs.navy.mil>]

There is no bright star at that location; there is a Tycho2 star
at 81.853 -0.586.  Did you possibly have a typo in the coordinates below?
Arne

Tom Droege wrote:
> 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
> 
> 
> 
>