Quote:
Originally Posted by Ribodab
Maybe you should look to see why they use refractors, so many more advantages and in astrophotography unless planetary its not often about aperture, an f5 4 inch refractor will still have a shorter wider field, often Newtonians, unless modified may not be able to get enough focus. The defraction spikes can be bothersome. One of the best astrophotographers on You tube, Trevor Jones often uses a small 4" apo and even a 60mm and would not even know were done on a small aperture. With astrophotography light continues to gather and build up, unlike the eye. Also a bigger scope can give poor results due to atmosphere contains and a refractor often gives better steadier conditions. Beginners don't often grasp that in astrophotography its not always about aperture less important than for planets and visual, both totally different.
Also the bigger the scope the more beefy it needs to be and most costly. Also more likely effected by wind and collimation issues
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Hi R,
I don't need to see why
others use refractors: You are preaching to the choir as
that's all* I have: refractors. I understand and have espoused their potential advantages (no central obstruction, contrast , etc....) a few times. My point was about aperture, focal ratio and entendue. I did not say that needed to be achieved by using a reflector as excellent as some are.
Best
JA
*Full disclosure - sorry I did forget one (unused) 10inch Newtonian