[Aavso-photometry] Ensemble photometry question

[Robert J. Modic]

Thanks Pertti and Arne.  Let me clarify what I'm trying to 
do.  I already know the errors of each comp star (taken from 
one of Arne's .dat files for example).  I'm just trying to 
calculate the portion of the error due to the ensemble of 
comp stars.  Adding all the errors in quadrature results in 
an error that is too large.  I then tried dividing the previous 
result by the square root of number of stars used.  This gives 
an error that is very close to a simple average of all the 
comp star errors.  Since the error should be reduced by the 
square root of the number of comp stars, the result of this 
second method still seemed too large.  The only way I can 
calculate an error that looks right is to add all the errors in 
quadrature and then divide this by the number of comp stars
(not the square root of the number).

I read the Honeycutt paper on ensemble photometry.  The
methods mentioned in that paper are meant for a non-homogenous
set of comp stars and seem too complicated for the more
simple type of homogenous ensemble photometry that I'm trying
to do.

Again, I'm just trying to find a simple way to calculate the 
component of the error due to the comp stars (the zero point
error).  This will then be added in quadrature to the other
errors (measurement, transformation, etc.) to get my total
error for each magnitude measurement.

Bob