Quote Originally Posted by Paul McSweeney
However a Canon 600mm f/4 hasa bigger aperture than the telescope you used, which was 600mm f/7.5 if I read it right. I have no idea which is more expensive. The canon lens is not cheap.

I'll bet the 600 f/4 would do far better (due to its larger aperture) than the 80mm Celestron ED, but it is much more expensive and much heavier (thus requiring a far more expensive mount). A more balanced comparison would be between a fast 6" refractor and the 600 f/4, or between a 5.5" refractor and the 800 f/5.6.


Quote Originally Posted by Paul McSweeney
In my limited exposure to telescopes I've encountered the term "light bucket"

The term "light bucket" originally referred to a large aperture telescope of not-so-great optical quality- usually a large dobsonian. Today people use the term for any big dob (I've never heard anyone refer to anything but a dob as a light bucket). The term, as far as I know, has nothing to do with focal length. But today's big dobs are getting *fast*. f/3.3 in apertures of 20" and up is no longer unusual.