[Aavso-photometry] Errors on AIP

[Radu Corlan]

On Thu, 15 Jul 2004, Pertti Pääkkönen wrote:

> On Wednesday 14 July 2004 23:17, Radu Corlan wrote:
> > > Finally, yeah, I'm not sure how to integrate the read noise into the
> > > noise equation. I'm just adding it in quadrature now. Otherwise the
> > > noise equation makes sense to me.
> >
> > To integrate read noise, you need to take into account your aperture; each
> > pixel contributes read noise.
> 
> ...and photon noise from background, readout noise in your bias, dark and flat 
> frames, scintillation, etc. as discussed in Radu's link. Too complicated, I'm 
> afraid most observers (me too sometimes) just send their observations without 
> considering the uncertainties too much.

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. So one needs only to do a full noise 
evaluation a few times, and verify that on typical images this holds. 
Then just considering photon shot (Poisson) noise for the fainter stars 
and scintillation on the bright ones will give a SNR number very close to 
that of a full noise model.

Radu

> 
> I do hope that some of AIP developers follow this discussion and implement a 
> proper SNR/Uncertainty estimate calculation (and astrometry as wel). 
> Meanwhile, it might be reasonable to use STD of your check star for your 
> uncertainty estimate.
> 
> Pertti
> 
> 

-- 

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

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