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

[Greg Crawford]

Working my way along the path to converting instrumental measurements to
standard measurements, I seem to have coped with Transformation
Coefficients. The next step is First Oder Extinction values. 

 

I have found that working with a small field of view (11'x 11' - an ST9XE at
f/10 on a C11) that not every Landolt Equatorial Standard field is as good
as another. Some put more stars in a standard field. Such was the case with
SA110. However, SA110 is drifting out of my sky. I got enough use of it
earlier on to nail T/Cs, but it sets too early now to use for F.O.E.s.

 

What are the best choices for First Order Extinction calculations? Must one
use Landolt Standards? Will Arne Henden's fields (culled for a minimum of 3
obs) do for FOE? Are colour differences important for FOEs? (I am hoping to
observe in V and R, or possibly I.)

 

I suppose my questions boil down to two:

 

Suggested catalogues of stars for FOEs.

 

Rationale for using those catalogues.

 

- Greg