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Star Diagonals


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Hi all.

This topic may have been covered some time ago, but I will ask the question again. I am contemplating upgrading my SD to either one with ED glass or one without, the two I'm interested in are the Sky-Watcher Gold ED 2" (with 1.25" converter) or the Stellarvue 1.25".

Which one (if any) is best and would this make my viewing experience better than using the standard diagonal supplied with my telescope? :icon_eek:

Thanks.

Richard.

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If you go for a 2" diagonal you have access to 2" eyepieces of course and the wide views they can deliver.

I'm not sure that the ED glass makes much difference as light does not travel through the glass in a mirror diagonal - unless these are the prism types ?.

Dielectric coatings are worth having as they are more robust over time than standard ones but the performance gains between modest and high cost diagonals are very slight IMHO. You may not notice the difference over the standard item, apart from better build quality.

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Thanks for the info John.

Just changing the subject for a momemt, I am also considering buying an APO barlow lens, but not sure if it would make much difference from a standard one or not?!

What do you think?

Many thanks,

Richard.

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There's a little confusion there. I've seen those both advertised on Buy'n'sell. The 2" is not ED, it's the standard Skywatcher 2" diagonal as supplied with the 'Gold ED Pro' scopes. Nothing fancy about it and a bit over-priced. Worth £30 tops really.

The Stellarvue is a really good quality Dielectric diagonal with 99% coatings. It's a step above the Skywatcher 2" above. The price is reasonable for that one too. If you don't plan to use 2" eyepieces, the Stellarvue is an excellent choice.

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Just want to say, just in case the seller is a member of SGL, that i'm sure he isn't deliberately over pricing the 2". With it being a larger diagonal, it could be easy to assume it's worth more than the 1.25" diagonal. :icon_eek:

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Regarding the barlow lens question... I have the Tal x2 and the Celestron Ultima x2, the Tal is a really good value for money barlow and well built. But it's not as good optically as the Ultima (which I believe is an APO barlow). Visually, I've not done any form of comparison, but I think the limiting factor under those circumstances is less the barlow and more my eyes :icon_eek:. Still the Tal doesn't get a lot of use anymore.

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The Celestron Ultima 2x and the Orion Shorty Plus 2x (which is a clone of the Ultima) are really excellent barlow lenses. The Tele Vue 2x barlow can be had for around the same price and is extremely good as well.

These 3 are another step up from the TAL but so is the price of course :icon_eek:

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It's not explicitly stated as APO on the FLO page, but it's a triplet

From the Celestron site

"This Ultima Barlow lens is, without doubt, the #1 choice among amateur astronomers who want the best performance from their optics. The Ultima Series Barlow (2x - 1-1/4") is an air-spaced, 3-element apochromatic design with a 27mm clear aperture. "

Ultima 1.25 in - 2x (item #93506) / Barlow lenses / Accessories / Products / Celestron.com

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