Count on this Brunton 50mm porro prism binocular to gather a lot of light. Fully multi-coated optics only increase the distant, bright views—especially important when observing planets and stars. The Eterna delivers classic performance with modern waterproof and fogproof protection. Brunton covers the Eterna with a limited lifetime warranty.
Fully Multi-coated Lenses
Increase light transmission with multiple anti-reflective coatings on all air-to-glass surfaces. FlatLight coatings.
Enhances resolution and contrast through roof prisms.
Optimize light transmission.
Generally offer a rich depth of field, wide field of view, and three-dimensional image.
Provides a secure, non-slip grip.
Roll up and down for comfortable viewing with or without eyeglasses.
Adjusts each binocular barrel independently.
Optics are sealed with O-rings to prevent moisture, dust, and debris from getting inside the binocular.
Barrels are filled with nitrogen gas to inhibit internal fogging.
Contacted Brunton and found these have not been made for about 10 years, and most importantly they no longer carry spare parts for repair. They will honor warranty issues by selling new equivalent roof-prism version at steep-steep discount.
**************************** The exterior: Very well built. "Feels" as sturdy, and as heavy, as my 30y.o. marine Meibo fujinons, though the pivot isn't quite as smoothe. Ranging reticle in left barrel. Rubber armouring is fairly "grippy", which you would hope for in an instrument meant for a marine environment (though mine have only been used on land... I can't even say I've used them in a drizzle.) The anti-reflection coating (AR) is a deep purple/violet and not the idiotic "ruby" that has become de rigour now-a-days, which was originally developed as an anti-laser blinding coating for military use (how many of us have to worry about that, now really?).
Objective covers are attached, and fit well, though a bit hard to get on and off. But that's understandable as the objective housing is rubber coated. The strap that attaches the cap to body is not a separate piece, but rather a molded extension of the cap, therefore it is very stiff (fine for the caps, but not straps) and the caps do not "hang" well and tend to get in the way. I'm seriously thinking of cutting off the molded straps and finding someway to attach the covers/caps with a longer nylon cord; perhaps super gluing or expoxying the cord to the caps. Probably not very pretty, but more functional.
The individually focused eyepieces move very smoothly and stay at focus once set, I.e. they don't float around. Focusing is done by twisting the metal knurled barrel of the eyepiece. I do wish the knurling was a little more prominent/rough/grippy, as they are rather slippery with sweaty or greasy fingers. The eye guards are the fold/roll down type, rather than the (to me) more preferable twist up-and-down type. But at least once they are rolled down they stay down - have a problem with a pair of binocs, that I otherwise love, where one of the roll down eye guards won't stay down, which is a problem as I usually wear glasses.
The View: The view out of the right barrel (without ranging reticle) is nearly SPECTACULAR. It is incredibly bright; with no apparent coma, and with just a bit of pin cushioning at the very edges, and that's only noticeable when you really look for it. When doing the "streetlight" test (look at dark skies at night with streetlight just out of view) I detected just the faintest blooming at the edges - these are very well AR-coated, and probably very well internally baffled. When looking at the edge of a bright half-moon, I could detect no double-imaging, which would have indicated problems with internal reflections. I would put it on par with some of the more expensive binoculars I have, or have tried, such as mid-level Nikons and Leopolds.
The left barrel (with reticle) is just fairly good - there is blurring at the very left - maybe 1-2 percent of that edge, and much much less than 1% of the total field. Also, against a very very white background, there seems to be some yellowing of the field at the very left edge. I can't help but think these two things are related. Is the reticle cemented into the optical path? If so, then perhaps the cement is separating or degrading? Or if the reticle is its own independent piece in the optical train then perhaps it is slightly out of adjustment? Oh, and the left overall view is just slightly less bright than the right...hmmmm, it makes me think the reticle is seperate - it's another two air-to-glass surfaces that reduces light transmission. Though if it's cemented perhaps it's degrading? If it's degrading maybe it has lost its nitrogen purge and moisture and/or oxygen has entered the barrel???
[This is why I called Brunton technical services, but I got side tracked when I found out about there being no replacement parts.]
Another problem (though this could be considered nit-picking) is my ranging reticle is about ~5* canteded up on the left from horizontal. I do understand this is because my eyes are rather far apart (when you adjust the barrels for separation it swings the barrels around an axis), but to get the reticle to match the binoculars at horizontal the barrels need to be pushed nearly all the way together. Meaning that when the barrels are set at midway (which I assume is "average") the reticle is canted 2-3* up on the left. I contend that they should be flat at midway and would be only slightly canted, one way or the other, when separated minimum or maximum.
Conclusions - If the left barrel of the binoculars were as awesome as the right barrel these would be hands down a superior set of binoculars (even with the other drawbacks and problems). But with the problems of the left berrel, and there being no replacement parts for repairs I can't really give these "two thumbs up". Now, perhaps I was just "unlucky" and got a lemon (it's too late for me to try and return mine to the retailer as I've already put them to a season of use - I have been using them as my baseball binoculars - Go Giants!) and you were to buy these and not have any problems with the reticle barrel, then these would be a "very good" buy. I couldn't give them an excellent buy since there are no repair parts for possible future problems. Now, if there were repair parts.......