TRUGLO Tru-Brite 34mm x 24mm Hunting Shooting Durable Lightweight Compact Parallax Free Waterproof Shock Resistant Adjustable Red/Green Dual-Color Dot Sight | Battery Included

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.

Update: July 16, 2014Had to reapply loctite on the screws several times...laser battery is still working fine. The housing has been scratched up, but the dot and glass still look great. Would I buy again for another gun? Short answer, no and here's why...After having it this long, it's a good cheap red dot, great for plinking...maybe for a 22...but if I were to give this to my wife or kids to bet their life on...not a chance. The constant screws coming out and becoming loose is a major cause of concern. If...this is just used on a home defense gun, I could see it fulfilling it's purpose as long as it's properly maintained. But heck no to any sort of combat situation and hunting. If the sight gets hit at the right angle, it breaks the loctite glue seal...and then loosens up all over again. I'm retracting a star for this reason.Summary:Good for home defense, cheap red dot, if not used much after zeroing.Good for 22 plinking.Not recommended for hunting and combat zones (though the combat zone situation should have been a "duh" from a $90 red dot).I have since REMOVED THE RED DOT and replaced it with an aimpoint as my wife and kids depend on the rifle now as their means of protection while at home. This red dot is now "retired" until my 3 year old gets old enough to get her own 22.Original Review:For $90 I wasn't expecting an Eotech or Aimpoint, but I believe I've got more than what I would have asked for. This sight is very well made and despite throwing my AR15 to the ground with it multiple times it still works and holds zero. I did apply Loctite around the screws and suggest that you do the same (shouldn't everything on an AR15 be loctited? Besides quick release detachable mounts). This red dot does seem to tilt a bit when it goes on the gun as it doesn't quite look like the groove under it was meant for current rails which is odd...I plan on grinding it to fit perfect, but the slight crookedness of it does not bother me at all.This Red-dot has been through over 3,000 rounds and has been removed from the AR 4 separate times for a real cleaning. In does hold zero, but it MUST be loctited!!! The twist screws will not hold the red dot zeroed for more than 2 magazines before you start to see an issue.Would I buy another? For a recreational gun or cheap defense dot on something - yes...If I were going into a combat situation I still do not feel entirely confident in it even though it has survived multiple drops. If It changes my mind after another year of being tortured in classes, I'll let you guys know.Until that point, it's a great sight for the money and if maintained, it will perform exceptionally. If you have questions about it just let me know.