|
1 - very roughly, the light cone is so narrow at high powers that the barrel does not need to be 2" wide. It varies a bit with the focal ratio of the scope - faster scopes need wider barrels before slower scopes. Manufacturers seem to choose 26mm as the transitional point between 1.25" and 2".
2 - maybe add a barlows to provide more use for your existing eyepieces. a 1.25" X2 barlows will effectively add a 6.5 and 5 etc - although you might want something in the 20mm range.
3 - on those rare nights of really good seeing you can really up the power, a 5mm planetary with good eye relief or barlowed existing 10 or 12.5mm eyepiece will certainly give you the possibility of some great views of Jupiter etc. The problem with a dob is that you have to tap it round and then let the planet drift across the view (you cannot follow it manually), rinse and repeat. It only take 10-20 seconds to cross your view at high mag.
4 - sorry I do not follow your question here
cheers
|