[Aavso-photometry] Need High-dec (B-V)~0 stars & Secondary Extinction Pairs (3 new additions for your lists);

[arne]

Daniel Majaess wrote:
> Hi, I've derived the local parameters for Halifax Nova Scotia by 
> following an extinction pair across various values of airmass and the 
> secondary coefficients appear to be essentially zero---especially in the 
> visual band.  So I am now thinking of shifting gears and adopting the 
> protocol outlined in Henden's book whereby a bunch of different stars 
> (at varying airmass) with (B-V)~0 are imaged.  I was wondering if anyone 
> had a list of high-dec, bright (7.5-9.5 mag) stars with a color (B-V)~0, 
> and also they need to have well-defined visual and blue magnitudes so 
> Hipparcos data will not cut it.   Any suggestions would be lovely =)
> 
> Also, here are some nice secondary extinction pairs that I am using and 
> you may want to add to your respective lists.  I *believe* I got them 
> from scanning through Dave Lane's ECU but I was sent a number of 
> suggestions from wonderful AAVSO members =)  Anyways, here they are: 
> HD96730 ( 11:06:52.69 +36:42:29.2 ), HD 97184 ( 11:16:01.55 +42:24:01.0 
> ), HD92454 ( 10:42:31.14 +68:34:22.2 ).
> 

Certainly there is a list in Henden's book of bright zero-color (A0) stars.
As for Hipparcos stars (such as Richard Miles' nice red-blue pair list),
I wonder why you feel that "Hipparcos data will not cut it."  For
the all-sky extinction method, you only need stars with approximate
zero color, as transformation is a second-order effect.  For example,
say that you have one star with zero color and another with
(B-V) = 0.2  (Hipparcos colors are *much* better than this!).  If
your V-band transformation coefficient is 0.05, pretty typical, then
the error made by not transforming the instrumental magnitude of
the second star is 0.2*0.05 = 0.01mags, which will usually be about
your limit for handling all-sky measures.
Arne