Quote:
Originally Posted by codemonkey
Now if the bigger aperture means that more light is focused into an area of the same size, I can see why the intensity would increase...
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For a given camera, focal length dictates field of view, nothing else. An 800mm FL f2 scope with an aperture of 400mm will have the same field of view as an 800mm FL f10 scope with an aperture of 80mm. In these systems, the only difference in the final image will be the light collecting area defined by its clear aperture. I think you would do well to google a ray trace of a telescope, what is happening is light from the star or nebula or whatever you image hits EVERY part of your mirror and it is focused onto the sensor. That is why bigger mirrors (for a set FL) will give brighter images.
Another way to show this physically, would be to put a longer focal length eyepiece into your scope. going from a 30mm to a 3mm (increasing magnification) makes the background darker.