Astromania 2 Inch Diagonal 45-Degree Erect-Image Prism for Telescope - Image Erecting BAK4 Prism with Anti-Reflection Coating That Provides Sharp and Clear Image - with 2 to 1.25 Eyepiece Adapter

Good daytime diagonal with decent clear aperture. 21 Ethos doesn't have noticable vignetting, but 41 Pan obviously does. Works well until about 60x, then the chromatic aberration is quite noticable, which isn't there with a mirror diagonal. Daytime use above that is rare anyway. I would not recommend this for planetary viewing.This diagonal helps target quickly moving things better than a 90 degree mirror diagonal becuase one can look at the target more easily while adjusting the scope. It is also better for horizontal and downward viewing than a 90 degree diagonal.The 2-1.25" adapter is recessed to more easily allow 1.25 eyepieces come to focus - focus gets pushed further out than with a mirror diagonal. However, the recess interferes with securing eyepieces with hybrid 2 and 1.25" barrels becuase of the recess. Consider a flat top adaptor for those hybrid barrel eyepieces, or be very careful.

The finish quality is commensurate.If you need a 2 inch 45 degree erecting prismThere are few options.

I tried to find a used WO, Astromania, etc. 2", 45 degree erecting prism diagonal for several weeks. Thought I'd found a used on via Astromart, but it turned out to be, lets say, not in the condition I wanted for my collection, and he wanted $145 for it! Not! Kept looking, and came across this Astromania unit being marketed thru Amazon. To my eyes, it looks exactly like a William Optics unit, and the build quality is excellent. I immediately took the eyepiece and tried viewing several nearby terrestrial objects through my TV-85, and I was pleased! The "kicker" to all this is that I bought the diagonal new for just $15 more than the extremely well-used unit offered thru the Astromart website! I highly recommend you try this out. You'll be impressed!

Works very will and allows me to use my existing 2" eyepieces for terrestrial viewing. Seems quite well made. Not something I'd use on astronomical objects but works well for terrestrial views and the moon.

I purchased this item through Amazon but returned it when I found it to be incompatible with a Vixen VMC200L telescope (also purchased through Amazon).- The product is well designed and very well made. These are not just words; I intend to purchase other Astromania products.- It introduces a significant optical path that prevents proper, astronomical focus with a VMC200L. Proper focus with closer, terrestrial views can be obtained. Astro-focus can be obtained with some other telescopes, but Caveat Emptor.- The prism seems to be a full aperture Amici design (a marvel of optical science). By "full aperture" I mean that both paths are used; each conveying half of the image. While some might quibble, the design works quite well for terrestrial views. For astronomy (I used a Williams Optics refractor for this test), where many objects are little more than unresolvable pinpricks of light, an edge of the prism introduces, vertically, a significant diffraction spike: each star appears to have a line extending vertically. -- That spike is hard (impossible for me) to detect with terrestrial views. -- If Astromania were to use a larger prism, the spike could be mitigated, but the prism would be enormous ... easily twice the current size. -- The VMC200L, because of its optical design, introduces its own spikes, two of them ...a matter of minor controversy, not germane here expect to note that the Hubble Space Telescope does too... but one of the spikes just happens to line up with the one produced by the prism.One final note: the Amazon return process (I think this was Amazon Prime) was so surprisingly simple that it caused me some consternation.I expected to have to pay for shipping ... it was free.I expected to have to pay a restocking fee ... I didn't.Five stars for that.

I got this for one of my telescopes for viewing land and lunar things. Aberrations on the fringes of ALL Amici prisms will preclude getting great views of Stars except maybe Sol. So, getting one for viewing deep space is probably not what you want. It gets five stars for being well built and performing as well as any of my other, but smaller, Amici Prism Diagonals. Looks great too!