Quote:
Originally Posted by AXE
The Esprit comes with a flattener included, as far as I've read there's no reducer out there that can be used with it.
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Well, that makes it a simpler comparison then. The FOV will be similar, the speed will be markedly different, guiding will be probably not easier but potentially more accurate with the refractor due to being able to use an off axis guider.
I was actually looking for a good explanation of factoring the F number to imaging speed and found one on the CN forum.
Without using actual figures. Take a given scope and call it F5, say that particular scope at F5 with your camera is at a scale of 1 arc second per pixel and a particular arc second of sky has 100 photons arrive in a given exposure time, those 100 photons will all fall on 1 pixel. Now double the focal length (F10) of the same diameter objective, the image produced at the focal plane will double in size, each pixel is now seeing half an arc second. 100 photons arriving in that same arc second of sky are now falling on a 2 X 2 pixel grid so it is 25 photons each, you need four times as long to gather 100 photons per pixel compared to the "Faster" setup. The resolution of the image is higher, but if seeing limits the resolution you don't get any benefit from that.