Astromania 1.25 Inch Telescope Diagonal with Amici Erecting Prism - 90° Fully-Coated Star Diagonal for Upright & Clear Astronomical Viewing, Metal/Plastic Construction, Enhanced Optical Transparency

Almost all my other 1.25" barrel 'correct-image' 90d diagonals have a SMALL Amici prism, which vignettes the field and dims the view with longer FL eyepieces. This one is better made, with nearly the same available field as the barrel diameter; so it works MUCH better. Could not be more pleased! What *does* bother me is the odd disparity of some other reviews of the same item. (I was the Product Development manager at perhaps the largest US telescope accessory retailer/marketer, with 60+ years' experience in amateur astronomy.) MY copy of this Astromania diagonal is NOT 'dimmer' than a mirror unit, as claimed by another party. I have tested it against two name-brand standard aluminized 1.25" mirror star diagonals, and this Astromania prism diagonal seems to be as bright--in fact, it was noticeably brighter than one, and the equal brightness of the other. Did we get the same product? Furthermore, after closely examing my unit's prism under exactly the right angle of broadband light, I can clearly discern an anti-reflection overcoating; the other reviewer says there was NONE, contrary to the ad. Not so in my case. He objected to spurious reflections (which I also do not see) and says that the eyepiece-side should be masked. My unit IS masked. So I have confidence that my eyes did NOT deceive me; and I have no reason to change my top 5-star rate.

My wife was given a starter telescope for her birthday that came with cheap starter accessories. Among them was a cheap Erect Image 90° Diagonal that was just a mirror. This Erect Image 45° Diagonal Prism gives a much crisper image, has the correct orientation to what you see with the naked eye and the angle is more comfortable for viewing. I have a moon filter for viewing the full moon without it being too bright, and (after testing) I'm able to thread it onto this prism which was a huge selling point for me. I have tested all connections and combinations of my accessories including my 5x Barlow, which clears the receiving end without getting close to the prism. I love what I've seen so far from this prism and recommend it to any fellow amateur astronomy fan.

The unit I got is a mixed bag. The important bad thing is it has NO anti-reflection coatings. The face reflections are white and bright. The important good thing is the prism is very accurately made. I checked it with a very good SV ED50mm F6.6 scope at 55X to 110X on a 3 bar resolution target, and the image is as perfect as the scope image with no prism. The aperture is on the small side - 21.7mm, so it will vignette with eyepieces longer than 25mm EFL. The body looks like cheap molded plastic, no surprise there. The barrels are quite decent - 1.498" OD, 1.253" ID. I'm pretty surprised at the optical quality hence 4 stars. Amazing how they can made perfect roofs now for cheap. Given a choice I'll keep good optical quality and no AF coatings, and I'd reject bad optical quality no matter how pretty the coatings are. I'm not using this as a diagonal, so I wasn't too concerned about the optical quality. I would like the missing 7% light though, but not so much I'll send it back.

metal and works well

I purchased this because the refractor on my new telescope was having too much glare. This one has less glare and a clearer view. Visuals are right side up, left and right. 1.25. Nice tightening screw. Doesn’t feel cheap. Has a nice weight to it.

Good product for the money

Great telescope accessory very bright and value for the price

Very solid despite being plastic body. Strong stay screw won't mar and holds securely. Prism arrived clean and sharp views up to 120x. Edit: I discovered I can mount my Calcium Quark and surely Combo Quark to this 1.25 for ultra low magnification image correct views not limited by seeing conditions! Sharp to around 100x, solar needing 50x only, this distant Quark view still has all the detail of a greater magnification without being ruined by seeing. Transforming solar observation!