[Aavso-photometry] Choosing Stars for F.O.E.

[arne]

Bruce Skelly wrote:
> Arne,
>  
> Is there a cut of limit to the magnitude that one should use with A0 stars?  For example, below a certain magnitude, an A0 star is so distant that there could be too much interstellar reddening.  The stars listed in your book are quite bright, for a CCD.
>  
It is true that as you go fainter you are more likely to find an
obscured star.  However, at the limits you are likely to use (say,
11th mag), this should not be a problem.  You can check the Tycho2
BT-VT color index to ensure "zero" color.

Below 18th magnitude, everything is a galaxy anyway. :-)
Arne