Advice/opinions on diagonals

[Darth Wader]

Hi all,

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.

Cheers
Wade

[erick]

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.

[Darth Wader]

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!:lol: Thanks for your help Eric.

Cheers
Wade

[erick]

I have this one:-

Bintel Star Diagonal 2"Quartz (SCT)

Came with the SCT I bought secondhand. From an optical point of view, I don't even notice that it is there. It's probably pretty good?

[acropolite]

Ditto what Eric said abouit the GSO quartz dielectric, excellent diagonal at a reasonable price.

[wavelandscott]

I'll add my "me three" to the GSO quartz dielectric...

[dannat]

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

[Darth Wader]

Hi Daniel,

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.

Cheers
Wade