[Aavso-photometry] Errors on AIP

[Radu Corlan]

On Thu, 15 Jul 2004, Michael Koppelman wrote:

> For the SNR, yes, I believe this to be true. The "total" error (total 
> in quotes because I doubt there is such thing) the comp star sigma 
> generally dominates. 

Sure; i was reffering to the SNR of a single instrumental value. It's 
generally very useful to use more than one comp star, because this way not 
only you reduce the noise contribution of those, but you can detect a host 
of other problems (if the comp stars don't fit by more than their expected 
SNR, you detect that there some kind of error (bad comp, thin clouds, a 
wrong filter etc).

Radu

> Currently AIP users can use the K-C standard 
> deviation as their error and get most of the way there. However when 
> the comp stars are brighter than the target, one should really factor 
> in the shot noise as well.
> 
> One other note: AIP has a way to figure out your gain and readnoise 
> that is very quick and easy. It's under the "Measure" menu and is 
> called "Characterize CCD Camera". My spreadsheet requires this info to 
> be accurate.
> 
> Latest version of the spreadsheet is here:
> 
> http://www.lolife.com/astronomy/AIP_Err.xls
> 
> Michael
> 
> 
> On Jul 15, 2004, at 6:50 AM, Radu Corlan wrote:
> 
> > One important thing to note is that in most cases, if the sky is not
> > _very_ bright and the aperture is not too large, photon shot noise
> > dominates by a good margin.
> 
> 

-- 

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Radu Corlan       Snail Mail: Bucuresti sect. 1, 
rcorlan at pcnet.ro  str. Argentina nr. 28, Romania

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