Diagonals ... quality under scrutiny

[emadmoussa]

I always had doubts about the quality difference between different diagonals.

The Di-electric 2" one that comes with the 80ED DS Pro supposedly has a 99% reflectivity. It feels like a quality item and the views through it are pretty good indeed.

Also, I've got a Telescope Service 91% reflectivity 2" diagonal, which by comparison with the Sky-watcher version above didn't show less or better image quality. Unless the Sky-watcher version is not 99% reflectivity.

Which makes me wonder, in this sense what does for instance make the William Optics of a similar caliber cost thrice as much as the Sky-watcher?

I tried a bunch of 1.25" diagonals (you know, you always get one with every new SCT or refractor) and for the life of me didn't show less noticeable quality than other versions twice or three times the price. 2" diagonals are a different case.

I was looking at a WO quality diagonal to replace the TS for the 6" refractor (since I need the best of quality for DSOs) and now I'm starting to have serious doubts about having better quality than what I already have at the moment.

What's the catch? Am I missing something here?

[David Smith]

Interesting. I have a bog-standard Skywatcher diagonal as came with my Evostar 120 but nothing to compare it with. I was considering an upgrade but think I will hold off and see what responses you get here

[emadmoussa]

Interesting. I have a bog-standard Skywatcher diagonal as came with my Evostar 120 but nothing to compare it with. I was considering an upgrade but think I will hold off and see what responses you get here

Same here.

[jgs001]

There was a comparison done some time ago between the different diagonals, and from memory the general conclusion was that the premium diagonals didn't show a significant improvement over the basic ones. However, the build quality variation is significant. I upgraded a basic to a WO (second hand) and it feels a lot more sturdy and well made.

A couple of threads

http://stargazerslounge.com/topic/65466-can-we-have-a-discussion-on-diagonals/page__hl__diagonal%20comparison

http://stargazerslounge.com/topic/18781-diagonal-dilemma-%E2%80%93-part-1-updated/page__hl__diagonal%20comparison#entry198088

[m.tweedy]

I went for a baader clicklock

http://www.harrisontelescopes.co.uk/acatalog/Baader_Clicklock_Diagonal_2_.html

Not because the views were better BUT when you have big ethos eyepieces the locking system is superb. It holds like a vice but can be undone with cold gloved hands in safety. I always felt the weak point was the little thumb screw that was holding something heavy and expensive.

[earth titan]

I went for a baader clicklock

http://www.harrisontelescopes.co.uk/acatalog/Baader_Clicklock_Diagonal_2_.html

Not because the views were better BUT when you have big ethos eyepieces the locking system is superb. It holds like a vice but can be undone with cold gloved hands in safety. I always felt the weak point was the little thumb screw that was holding something heavy and expensive.

I also use the Clicklock on the back of my SCT, but put a diagonal in to that. I think the system is brilliant.

[Pig]

Unless it is a very poor unit the human eye would probably not be able to determine any difference.

Collectively throughout the whole set up you would notice a difference if there is a weak link.

You wouldn't buy an Aston Martin and put remould tyres on it.

[John]

I've used loads of 1.25" and 2" diagonals from the stock ones to expensive units like Tele Vue Everbrights. It's one component in the optical chain where I feel spending lots of money seems to deliver the least significant gains in terms of optical performance. Mechanical security for heavy eyepieces is one thing that the better built ones do deliver though.

I've currently got three 2" dielectric diagonals, an Istar, a GSO / Revelation and a Tele Vue Everbright. The new prices of these range from £89 to £240 but optically I can't tell them apart. The Tele Vue is better engineered than the other two though.

[nightfisher]

I have a dialectric bought used and a Tal one, both are very good but the tal one has a great feature.......it can be collimated

[Moonshane]

I agree about build quality. to my knowledge the Televue ones are CNCd from one block?

[John]

I agree about build quality. to my knowledge the Televue ones are CNCd from one block?

Yes they are. Neat bit of engineering and nothing can unscrew

[emadmoussa]

Speaking of build quality, the TS piece is actually built like a tank...seems like one chunk of metal