[Aavso-photometry] Ensemble photometry question

[Pertti Pääkkönen]

Hi,

I propose that you should associate a noise N_n = ADU_n/SNR_n for each of the 
comp stars n. Then sum the squares of the noises and take the square root to 
get the total noise N = sqrt(sum(N_n)). Ensemble SNR is then: SNR = 
sum(ADU_n)/N. Finally, the uncertainty of the comp star ensemble magnitude is 
Approx. 1.086/SNR. 

Pertti

On Wednesday 11 January 2006 12:19, Robert J. Modic wrote:
> I wondering what the best method was to calculate the
> total error of an ensemble of comp stars.  I know that
> the error decreases with the square root of the number
> of comp stars.  Since each comp star has its own error
> that is usually different from other stars in the ensemble,
> what formula should I use?
>
> Bob Modic (MRV)
>
>
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-- 
Pertti Pääkkönen, PhD, Laboratory engineer
University of Joensuu, Department of Physics, Finland
Tel: +358 13 251 3238
Fax: +358 13 251 3290