Amici prism diagonals - are they all the same?

[Ags]

I am thinking about getting an Amici diagonal for certain kinds of star hopping (or, in my case, star hoping). But which one? They will all show the same diffracting pattern so is it worth spending more?

Astro Essentials 90 Amici - £34

StellaMira 1.25" 90º Erecting Prism - £69

Baader T-2 90° Baader Astro Amici-Prism - £249

(prices courtesy of FLO)

The  Astro Essentials one sound like my kind of cheap and cheerful. Why is the StellaMira twice the price?

The Baader is however attractive as I guess it really is better and the T2 connection means I can use it for short light path applications (my Askar FMA135). 

[Roy Challen]

I had the Baader prism you mention, several years ago now, but I recall it being very good. I had a Tak prism at the same time and there was no difference visually. The Baader is considerably better built and easier to use, but way more expensive. Shouldn't have sold that one...

Can't say I ever saw any diffraction spikes. I used it with a Borg 60mm achro and my Skylight f/16.

Edited December 11, 2023 by Roy Challen

[Louis D]

For low power star hopping, I would stick to the lowest cost option available.  The Baader would probably shine at high powers, but who star hops at high powers?

Remember, though, the clear aperture on these lower cost Amici prisms is somewhat less than 27mm, so you will probably see vignetting with widest true field 1.25" eyepieces.  Also, they're plastic bodied, so I wouldn't put a heavy, expensive 1.25" eyepiece in them.

[Ags]

The Baader would be nice for Luna though...

[badhex]

The astro essentials appears to be the same as the synta prism that spear under SW and Celestron branding. They are not particularly high quality as @Louis D says, a pretty tiny clear aperture, and only have the one set screw so will mark your EPs, if that kind of thing bothers you.

The StellaMira is definitely a lot more solid and of metal construction with a compression ring, but the mirrored version has a lip preventing full use of clear aperture as mentioned on other threads. Since the body of this is the same construction one might assume it has the same issue.

I have the non-Amici version of the Baader and it is very good and solidly built, no issues with clear aperture (35mm on the Amici version) but naturally you pay significantly more for Baader, especially since the Amici version does not come with EP holder or nosepiece if needed. 

Edited December 12, 2023 by badhex

[Mr Spock]

I have a Celestron (bought on here) purely for use in the 60mm for birdwatching. It works just fine with my LVWs and the views are much better than actual birdwatching scopes! (well, it is a Tak )

I also have a 2" Antares. CA is so severe it's unusable at anything above x30...

[michael.h.f.wilkinson]

I only use a 2" Amici prism (William Optics made, by the look of it, but Orion USA branded). It works well at lower magnification, and plays nicely with the 2" Naglers I have. Birdwatching with an APM 80mm F/6 and Nagler 22mm T4, at about 22x magnification with a 3.75 deg FOV is just brilliant. I have used a 45 deg 1.25" Amici prism, but that was a cheap plastic affair that came with a little 70mm F/5 scope I converted into a finder scope. I quickly replaced that horrible plastic contraption with a TS 90 deg 1.25" Amici prism which is far more solid, and works well with heavier EPs. The prism can be seen here:

My test of the 2" Amici prism can be found here:

 

[Highburymark]

The Baader BBHS T2 is pretty remarkable. I can only just perceive a tiny ‘spike’ with a bright artificial star. For lunar observing at high powers it’s top notch.