A good erecting prism?

[ollypenrice]

I have a Meade-badged erecting prism for terrestrial observing in my elderly Tele-Vue Pronto. It's clean and in decent shape but I feel that the view is just a tiny bit milky or cloudy in places. They are not cheap to replace so I wonder if it's worth it? Has anyone upgraded to a good Amici prism and compared the difference? Or have any recommendations? I only need 11/4 inch.

Thanks,

Olly

[vlaiv]

This one looks decent:

https://www.firstlightoptics.com/diagonals/william-optics-125-45-degree-erecting-prism.html

Baader has similar one.

https://www.teleskop-express.de/shop/product_info.php/info/p2672_Baader1-35--Amici-Prism-45--with-24-mm-clear-aperture.html

Both of them have larger clear aperture than cheap versions by SW and Astro Essentials (24-25mm vs 19mm)

I have no experience with either of them, so can't say much. I do know that SW and other cheap versions are not very high quality (I used to have one that came with the scope - but gave it away).

 

[Roy Challen]

I had this one some time ago - https://www.rothervalleyoptics.co.uk/baader-t-2-90-amici-prism-bbhs-coated-diagonal.html

Definitely not cheap, but very good optically, at least as good as the standard Tak prism diagonal.

[johninderby]

I have one of the Omegon ones and find it excellent for use with my ScopeTech 80 f/15 where it is nearly as good as my regular Baader prism diagonal and at the other extreme works great in my Lumicon SuperFinder.

https://www.omegon.eu/amici-prisms-90d/omegon-1-25-amici-prism-90d/p,14172

Edited April 10, 2021 by johninderby

[Captain Scarlet]

I have the WO one that vlaiv pointed out, and am very happy with it. I use it for terrestrial viewing with my Skymax 180, my Intes M603 and my LZOS 105/650. I have said "Wow" on numerous occasions when looking at birds from a distance. It does show a single spike when looking at, say, Vega, but that's to be expected in any prism with a "roof" I think.

[ian_bird]

Plus one for the WO one Vlaiv suggested. I also have it. Top notch.

[ollypenrice]

Thanks to all who've replied. I really can't run to £225 because that's about what I paid for the Pronto itself!

It looks as if the WO and the Baader might be the same thing re-badged and, since your reports are favourable, that might be favourite. What I need to do first, I realize, is compare the view in my present prism with the same view using a good star diagonal (which I have) to see if my prism is really lowering the quality of the image, as I suspect. I realize the view will be inverted but it's the quality I'm interested in at this stage.

(For about ten years I've had a ratty TeleVue Telepod mount which I bought cheaply, very second hand. I finally got round to working out how to adjust it and, although it's still cosmetically ratty, it now works very sweetly and I'd like to have the Pronto-Telepod handy for grab-and-look moments when we have interesting animal visitors outside.)

Again, thanks.

Olly

[Peter Drew]

The star diagonal will give you an erect image but laterally reversed.  My experience with erecting prisms is that those with 90 degree angle seem to work best.    🙂

[Louis D]

I've been using a Celestron 94108 90° correct image diagonal for 20+ years in my 60mm finder scope to good effect.  I can't seem to locate it at any retailers these days, though.

[Don Pensack]

Search for "90° correct image star diagonal".  I found about 50 different ones easily.

Many of them on Amazon and eBay, too.

All have small clear apertures, alas.

[johninderby]

The big problem with the correct  image 1.25” diagonals on Amazon and eBay is that the “correct image” description is misleading and allmost all are actually just regular mirror diagonals. Many even describe their diagonals as prism mirror diagonals. 🙄 Bit of Chinese to English mistranslation I think.🤔j

I ordered a correct image prism diagonal off Amazon which turned out to be just a regular mirror diagonal, Tried orering another correct image prism diagonal and ypu guessed it turned out to be another mirror diagonal. Both of course sent back.

Edited April 11, 2021 by johninderby