Swarovski Optik BTX 30x/35x Eyepiece Module for ATX/STX Spotting Scopes, Dual Eye Viewing Mount Cap

'nuff said.

No, didn't purchase from Amazon -- got it at a birding festival (the Biggest Week that takes place annually in NW Ohio). But I see there are no reviews, so thought it might be helpful to give some impressions. I believe I'm the 2nd person in the US to buy one (the first was a few hours before me, that same year (2017), shortly after this new product became available. This is what they told me, anyway!Of all the pricey birding equipment I own (Canon, other Swarovski, Leica, etc -- most of which I DID buy on Amazon ;-) ), this has got to hold top-spot; it's almost intimidating, and I treat it like egg shells. It's probably not necessary, since it appears to be built like a tank. I admit I have not used it a lot -- it is a bit specialized (heavy, requires special tripod mount, etc.) -- and I haven't had much opportunity. This year I hope to really put it through its paces, however, and will update this review if I have something significant to add.First off, you'll have to get the balance beam support made by Swarovski (or come up with some similar solution) to stabilize the scope which, with this (or any other) attachment your scope will become quite rear-heavy. With the balance beam, you'll have a second point for the scope to rest on. Without it, the rear of the scope will tend to slowly sink of its own weight, pointing the scope progressively skyward -- yuck. You can tighten the tripod head to minimize this, but it's not good to have constant torque on an expensive fluid tripod head, not really designed for that.OK, the nitty gritty -- this is an amazing accessory. You get immersive, 3-D, crisp, relaxing views -- way more comfortable than the traditional one-eye viewing experience. You gotta try it, play with it, to really appreciate! I don't know how they manage to give a (pseudo) 3D experience, since you only have the single objective lens, so it can't really be achieved by parallax. But moving your head slightly side to side, the background of the image appears to move slightly relative to the foreground object you are focussed on. So it's an excellent approximation to normal binocular vision, and gives a feeling of depth that you don't get from a scope with one eyepiece.Oh, and its ingenious little finder "scopelet" on the side works remarkably well (keep both eyes open, look with one through the little tube, pan & tilt the scope to position it so the "target/dot" you see aligns with your subject, and then look back in the binocular eyepiece. You'll be spot on your subject, or nearly so. It takes a bit of practice with fast-moving subjects, but it's very effective.A couple of disadvantages. You lose the zoom function (mine, on an 85mm objective lens gives a constant 35x view). And I can't imagine digiscoping with this setup (I naively thought it might work to look through one eyepiece and photograph through the other, while you see exactly what you're getting, but it's a lot harder than it may seem, and it would be easier just using the traditional approach with a single lens eyepiece.) Finally, this is a very non-portable solution -- at least used on the 85mm (and of course the 95mm) setup. It just too large to comfortably travel with, so though I'm heading to Spain in a few weeks for my first birding experience there -- well, this fabulous piece of equipment will have to stay home. Sad.Worth the money? Depends on how dedicated or determined you are to have the best possible viewing experience. And your wallet, of course. I say, despite its occasional awkward shape and weight, it does provide breathtaking views of birds. It's funny, through binoculars, birds are always on alert, wary, and easily flushed -- they don't like a big lens looking at them (same thing with my big camera lenses). With a powerful scope, I see field-filling views of RELAXED birds, preening, singing, sleeping, or just feeding without the jitters; since I'm so far away, they ignore me. The scope with a traditional eye-piece offers that same secrecy, of course, but with this BTX eyepiece, it's just gorgeous.