I've got a Skywatcher 70x900 refractor and I'm slowly upgrading a few bits and pieces as time/money permits. I've got my sights set on a new diagonal but I'm not sure what I should be looking at exactly. Should I get a prism diagonal for "correct" images or just get a semi-decent mirror diagonal? I mostly use my scope for planetary & Lunar viewing, with a view to upgrade to an 8" dob in the next 12-24 months.
You won't need a diagonal with a reflector so you'll have to sell it at a mark down price.
But, using a refractor (or an SCT) without a diagonal for observing must be a real struggle (like me trying to use my straight-through finderscope at higher elevations - Ouch!).
Now correct image for star-gazing? I don't think so since you'll get used to the movement of the image versus movement of the scope and you can certainly flip/invert Stellarium (to name one planetarium program) views to suit your observed image.
It seems to my reading that the mirror diagonals are preferred. One mirror surface versus several surfaces/interfaces and glass transit in a prism should mean less light loss and no CA and other nasty things that light does when it transits glass.
Hahaha - I should have mentioned that I already have a diagonal but it's the cheap & nasty one that came with the scope! Just thinking of using my scope without the diagonal makes my neck hurt! Thanks for your help Eric.
Wade, the SCT 2" dielectric will not fit on your scope - an SCT focuses further back - i am pretty sure your scope would have a 1.25" focuser slightly limiting your options. Andrews Comms sells WO 1.25" diagonals - in either correct image or traditional (do you do any land viewing?-correct mage would be better) - from memory the WO are about $80, might be better if you are going to get a dob anyway to save your money - or buy a good ep instead
I had a poke around on the Andrews website and they have the Williams optics D-125D 1.25" Dielectric diagonal for $129 which I might go for. Thanks all for your help.
Thanks for your help Eric.
