[Aavso-photometry] [Norton AntiSpam] Re: Light box question]

[Ben Davies]

Guys,

Thanks for the replies.  It was the S/N ratio that I couldn't see how to 
resolve.  I assume that in this situation you are not going for the 1 
million electrons/pixel that Arne was mentioning in a previous post, and 
are trading signal for accurate frequency matching.  What is reasonable?

And Michael, you mentioned a "chip flat".  Could you explain what that is?

I too, have never had great success at completely removing the ghosts of 
stars in combined images.  I should see Dr Kao soon.  I will ask him 
what software he uses and report back.

Ben Davies

> Hello Ben
>  
> Mike did an excellent job of explaining the dither technique. 
>  
> Like everything in photometry, it has its limitations.  It is very 
> hard to collect enough images to get real high signal to noise ratio 
> in the flat.  As Mike said, you can spend more time doing flats than 
> observing.
>  
> The other trick, is to remove the stars from these flats.  For me, I 
> have NEVER been able to make them really go away.  I can always see 
> residual stars at a low level.  Perhaps there is a trick that I do not 
> know able. 
>  
> I guess the bottom line is that you must match the flat technique to 
> the problem you are working to get the optimum results.  What this 
> probably means is to try several techniques, and see which answer you 
> like.  This technique will not always be the same.  I can tell you 
> that I spend some time almost every day working on flat fielding 
> techniques.  Its that important.
>  
>  
> Clear Skies
> Gary
>  
>  
>
>
>
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