Quote:
Originally Posted by Camelopardalis
So, I understand the physics behind it, even while my attempts to articulate it may have been lacking previously 
But I have a question - and just to be clear - because I’m uncertain and would like to understand further, not because I’m trying to be funny 
What’s the deal with “extended” objects, and why are they treated differently? Surely they are photon sources subject to the same mathematics?
FWIW, I have example images of a popular galaxy taken with my 4” and with my 8” (with different cameras, so resolution +/- 10%), where the 8” shows better detail, comparable noise levels, but in 1/4 the exposure time. It’s not night and day, but I thought it was a worthwhile experiment. If anyone wishes to seem them, I will post... |
The quick and simple answer is that star sizes on your sensor are determined by the f ratio alone and the size of an extended object, by the focal length (let's ignore the effect of central obstruction). That has implications regarding resolution and S/N ratio.