[Aavso-photometry] UBV Photon Counting

[Jeff Hopkins]

Hello Gary,

Thanks for the message and information.

I use the "Yale Bright star Catalog" for almost all my star 
information. As I recall the AAVSO charts do not give the UBVRI 
values for the stars (just V or visual values). In addition, it is 
usually best to find a comparison star close in color and magnitude. 
With bright stars, finding close companions is usually hard to do.

Regarding the LX-90 UV problem, I too suspect it is in the corrector 
plate. It may be thicker of different material or both from the old 
C-8.

BTW, I was out last night doing UBV work on epsilon Aurigae. It was 
near 60 degress at 10 PM. Love Arizona.

Jeff


At 06:58 -0700 1/19/05, BailyHill at aol.com wrote:
Hello Jeff;

Saw your note about not finding comp stars within the field of your 
ccd camera and c8/lx90.  I too have been doing photometry from the 
suburbs of Boston, and doubt if Phoenix could be any worse.

Were you using AAVSO "F" charts.  I find that I use them exclusively. 
There are comp stars within a 10-12 arc minute field.  Most of my 
program stars (CV's and faint LPV's) actually have a comp and check 
star within 3 or 4 arc minutes.  I am using a field of 9 arc minutes 
(10mm chip and 3570mm focal length).

Is your ccd field smaller than this?

CCD photometry with a c8/lx90 focal length scope is certainly very 
doable.  Hope this helps.

I have no comment on your U and B transmission question with the 
lx90.   Perhaps it has something to do with the material for the 
corrector plate.

Clear Skies

Gary


-- 
Jeff Hopkins
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