Amici prism advice please???

[Mr Bond]

Not sure if this is the best area for this so apologies if inappropriate.

I bought a 2" 45 degree erecting prism for a smallish scope to use as a spotter ( a Tak 60). The optics with a diagonal mirror are terrific so I know the quality is there, but soften up considerably with the prism with a 20mm and under EP.

I'm using a WO Amici ( spotting scope type erector). I have a 1.25" version of the same which actually fares better, purely in terms of clarity per x mag.

Questions:

What is the best prism option you can buy, money no object?

What's the best value compromise option?

Is there an big advantage in a 2" over a 1.25" for purely daytime use, quality aside?

My recent experience makes me think the 1.25" version is like "stopping down" the optical system and thereby improving the clarity, am I misguided here?

Many thanks SGL.

[Peter Drew]

A mirror diagonal has only one face to consider, an erecting prism has four so much harder to achieve a high quality. The best ones seem to be the 90 degree versions. A mirror diagonal will give an upright image but it will be left to right reversed.

[Mr Bond]

This much I have worked out from experience Peter!

Thanks all the same. :-)

[Mr Bond]

That sounded grumpy Peter, it wasn 't meant to be.

Thanks for your input. ;-)

[AndyH]

Possibly the best(well made) prism is the Zeiss, as offered by Baader?

I've got an old Takahashi prism with the same listed specs as above. Pretty damn fine diagonal, with a stonkingly small light path which is very important for my Tal 200K. Bear in mind it's not an amici prism, so the view you're getting through the eyepiece is as you would through a mirror. ie: left/right reversed.

Andy.

[Mr Bond]

Thanks Andy. I'm after using the Tak also as a spotter so right way round/up is essential in this case.

[AndyH]

Deep pockets??

Here's an amici

http://www.teleskop-express.de/shop/product_info.php/info/p608_Baader-90--Amici-Prism---with-T2-connection-on-both-sides.html

[Mr Bond]

Deep pockets??

Here's an amici

http://www.teleskop-...both-sides.html

Plus £50-60 for the 2" fittings. Ouch.

Does anyone know if the 45 degree version is of similar quality?

[Pingster]

Sadly from what i have read the 45Deg version is never as good as the 90deg vers. Seems we never can have our cake and eat it.

Sent from my iPhone using Tapatalk

[melsky]

I have the 2" William Optics 90 deg erecting prism and can report that on my FSQ85 with ethos eyepieces makes for a very nice spotter scope

Mel

[YKSE]

Interesting,   Do you see straight lines close to any edge?

[michael.h.f.wilkinson]

I have the Orion-branded, but clearly WO built 90 deg 2" Amici prism and it is very nice in my APM 80mm F/6 triplet. Works very well with Naglers down to 12mm (40x), and is even usable at shorter focal lenghts. I posted a short review here:

http://stargazerslounge.com/topic/185261-proper-first-light-of-the-orion-2-90-deg-amici-prism-plus-the-home-brew-mount/

[alan potts]

I have a 45 degree one that came with my Baader Vario Finder and it is rubbish, it is outgunned by the 90 degree Meade 1.25, which I think is a prism, by a fair way. I have seen Zeiss make one which I am sure will please but it's a lot of wonga.

Alan

[steph]

I have a question  why you want to change your erecting prism in 1.25" for a 2". Is-it for 2" oculars ?

If you need to use 2" ocular, ok, and a 90° amici is better than a 45°.

But for day-time viewing with 1.25" oculars, à 1.25" amici is  better than a 2" because the light travel is shorter (more glass = more chroma). All in all, it's not normal that your 2" prism degraded the quality of the Taka. A bad item ? I own a 1.25" WO with a triple 80/480 apo and the image quality is great. I tried a WO 2" and it awas not better.

Sorry for my bad english (i'm a french guy ). You can read the response at the same question (1.25" or a 2" prism for day time use on a little APO) on the french Astro-forum, Webastro. It's here : http://www.webastro.net/forum/showthread.php?t=121478

[Nova Load]

Has anyone compared the Baarder 2in Amici erect image diagonal against the Williams Optics 2in Amici erect image diagonal when viewing deep space objects?

One website says that the Baarder has 96% transmissivity compared to 95% transmissivity for the Williams Optics diagonal.

[Dude_with_the_tube]

never had amici and erecting prisms,as such,cant comment on them,but the best one in 2" and 90 deg prism is this one:http://www.teleskop-express.de/shop/product_info.php/language/en/info/p612_Carl-Zeiss-2--Zenitprisma---im-CNC-Gehaeuse-von-Baader.html

[michael.h.f.wilkinson]

I would not be too concerned about the difference between 95% transmission and 96%. We are talking a loss of 0.011 magnitude, roughly. I very much doubt anybody could see that difference except of absolute borderline objects

[ollypenrice]

Deep pockets??

Here's an amici

http://www.teleskop-express.de/shop/product_info.php/info/p608_Baader-90--Amici-Prism---with-T2-connection-on-both-sides.html

This does look interesting. All the cheapish erecting prisms I've tried have been so-so or even OK in the daytime but hopeless on the stars and moon. I particularly wanted a correct view of the moon at one time because it is so much easier to relate to the charts that way. (I've stopped looking at the moon these days. Shame on me!!!)

Olly

[michael.h.f.wilkinson]

The problem with that Baader one is it is has only a T2 fitting, which means the clear aperture is distinctly smaller than that of my 2" version. The OO one I have holds up pretty well until about 100x, and requires very careful focusing.

[Rainmaker]

I have both the Baader Amici and the Zeiss T2 diagonals and there is very little between them in light transmission.

I am sure a light meter would record a difference but a couple of % doesn't matter.

They are both extremely well made, the Zeiss T2 has a clear aperture of 34mm, the Amici 31mm. 

Given you're using it on the Tak FS60, which has a focal length of 355mm, I would assume you use 1.25" eyepieces.

I see no reason for a 2" diagonal on that scope.  On my FS60CB and FS60Q the Baader Amici was a very good diagonal.

I now have it permanently on the FC76DC and only use 1.25" eyepieces.

I have only used 2 other Amici prisms of Chinese origin and both were visibly 'soft' and seemed to lack the contrast the Baader provides.