[Geoff45 (Geoff)]

Can someone explain the purpose of large format (2.5", 3", 4") focusers on some refractors or as an aftermarket focuser. As far as I can tell from a cursory check on the web, ccd cameras only come with 1.25" and 2" nosepieces, and eyepieces with diameter larger than 2" don't seem to be around.
Geoff