Quote:
Originally Posted by Satchmo
So in an F4 scope for a given number amount of time I have available I will be able to increase my signal to noise more efficiently than an F8 scope of same aperture as my raw image is already 4X brighter.
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For an equivalent aperture and the same exposure time the answer is no.
It once again boils down to the fact your are still dealing with the same number of photons in both cases.
The best way of explaining this is with an example.
Suppose with your f/8 scope you take an image of 4 equally bright stars. Lets assume the photons from each star fall on four separate pixels. You therefore have 4 separate pixel S/N ratios.
Now you change from f/8 to f/4 by reducing the FL.
All the photons from the 4 stars are now superimposed on a single pixel and saturation hasn't occurred.
While the photon count on that pixel has increased by a factor of 4 as has the signal, it is due solely to the sum total of photons from 4 separate stars. It is not the same as increasing the signal from a single star by 4X which will increase the S/N ratio (N=Photon noise) by 2X.
You would probably find the S/N value will not be significantly different.
Stan Moore's comparison image supports the case.
Regards
Steven