I bought this red/green dot sight to use on a camera for astrophotography. I chose Truglo because I have their fiber optic sights on a handgun, and those sights are both well made and work well. They left me with a positive impression of Truglo. I have experience with other red dot sights on telescopes, and after a friend had trouble finding the fully-eclipsed moon through her viewfinder with a 600mm lens on the camera, I knew exactly how to solve that problem. I attach the sight to the camera with a Higoo hot shoe to picatinny rail adapter: https://www.amazon.com/gp/product/B075D3BCF8/ref=ppx_yo_dt_b_asin_title_o00__o00_s00?ie=UTF8&psc=1The rail isn't perfect, the hot shoe 'foot' should be near one end, not in the middle. As it is, the rail extends far enough back that it hits you in the forehead if you try to look through the viewfinder. It can't be adjusted, and I haven't found an alternative yet. Also, if you position the sight on the rail so that the back of the sight is flush with the back of the rail (i.e., the sight and rail hit you in the forehead at the same time) then the sight's clamp hangs off the front of the rail by about half an inch. Oh if I could only move that foot half an inch towards one end of the rail! Anyway, if you use live view on your camera's screen instead of the viewfinder, you're good to go. But back to the sight/finder. You have a choice of red or green, and there are five brightness levels for each. If you see ghostly reflections well away from the dot, you've got it turned up too bright. There are some internal reflections in the glass that make the bullseye reticles look a little like you've got double vision, but they're not a problem, and they're not noticeable with the dot reticles, and you didn't pay $600 for this sight either. I bought the model with four selections for the dot/reticle, mainly to get the smallest dot possible (2.5 MOA), which is half the size of the dot in the fixed, 5 MOA dot model. I find that the bigger or brighter the dot, the less of your target you can see, especially if it's a faint target like a fully eclipsed moon. Having said that, when I select the 5 MOA dot on mine, and turn the brightness to the lowest setting, it's fine. I could live with the fixed dot model. I know that now, I didn't then. How big are those dots, really? The moon is 30 MOA across, so the 5 MOA dot should be one sixth the width of the moon. In use the dot appears MUCH smaller than that, maybe I have my eye further back from the sight than Truglo expects. The big brightness adjustment knob has 12 detents: 5 red brightness settings, 5 green brightness settings, and two off settings. It's a bit coarse and stiff to turn, which means it probably won't turn on accidentally and drain the battery, but it also means that after I've got the camera aimed, I'm not going to muscle that knob and risk knocking the camera out of alignment. The battery cover can be hard to remove, a tiny amount of Chapstick on the threads helps. While this may sound like a mostly critical review, in fact, I really like this sight. It does about 95% of what my fancy EOTech sight does for 1/10 the price. It's built to last two lifetimes: all metal, no plastic. Everything I'd change would make it cost more: anti-reflection coatings on both sides of the glass, extend the housing to 1/2" in front of the glass, to make it harder to put fingerprints on it, and smooth up that knob! But as is, I think this sight is a hell of a bargain. I highly recommend it.Addendum: This sight appears to attach only to Weaver or Picatinny rails, not NATO rails. Both Weaver and Picatinny rely on clamping to the edges of the rail for alignment, while NATO rails have a raised, flat top (no slots like Picatinny) and the object being attached to the NATO rail is supposed to sit flat against the top of the rail. While the width of a NATO rail is essentially the same as Picatinny, the raised, flat top is the problem. The forward mounting screw on this sight is purposely mounted low (see the third picture) so that its square shank will sit in one of the slots on a Picatinny rail, preventing sight movement. That screw hits the top of the NATO rail and holds the front of the sight so high that the rail and clamp won't even engage. I checked to see if the screw could be rotated out of the way (i.e., an asymmetric shank) to provide NATO compatibility, but no, it can't. So, if you have a NATO rail, this is not the sight for you.