I purchased these to be used as a sighting aid out in the observatory and for casual stargazing on the rare occassions when i get to a dark sky site.
The three most important factors i was looking for in 20x80's were light weight and good balance; sharp optics; and a preferrably "immersive" wide field purely for aesthetic viewing pleasure. What i wasn't worried about was rugged construction, waterproofing and attaining the ninth degree of light conservation. I was impressed by saberscorp's comments about the handling of the Barska 30x80's and hoped these would be similiar.
This area respresents a *very* pleasant suprise. The actual weight of these binoculars, (postal scale of known accuracy) ready to use is 2kilo, 40 grams; 72 ounces or 4-1/2lbs. The balance is supurb. I have less problem handholding these 20x binoculars in an adequately steady manner than I do the 12x50's i own! A very pleasant suprise. I rather hate tripods as they remove so much of the freedom of movement that I personally feel is *the* key advantage of binocular observing generally. Other than for precision use (as in the resolution testing i will get to shortly or doubles stars etc) I don't feel anything more than a simple monopod is necessary for absolutely satisfactory steadying of these binoculars.
As far as tripod use goes, I find the sliding attachment bar assembly very useful. The position of the binocular can be adjusted so as to provide more clearance from the tripod when viewing near the zenith than would be possible if the attachment point was fixed near the main body. It also allows more positional flexibility when using the monopod.
Eye relief i did not measure but i *can* say it is most probably inadequite for eyeglass wearers.
All framing, including the barrel bracing and focus assembly plate *is* aluminum, the armoring is cursory and the barrel end pivot is not shimmed tightly and the focus assembly is not exactly built like a rock (although i must say it is much sturdier than the focus assembly on a vintage Japanese-made pair of Bushnell Rangemasters 7x35's I own...)
Diopters are not of an extensive range but I find it more than adequate. Others may not. They are not marked per dioper number, just plus/minus and their range of rotation is on the order of 180degrees stop to stop. the rotation is smooth and without play.
Focusing is very smooth and sure. No issues here. I did not notice any focus shift from eyecup pressure.
Hinges are tight and without play with the exception of the far barrel hinge which does have a small amount of noticable play when the barrels are pressed hard together. This seems to have no operational relevance in use, however.
These binoculars are multicoated on the eyelens and objective lens *only*. The visible prism reflections appear single MgF2 coated judging from their blue-toned reflection. The multicoating that is present seems equivalent in degree of it's reflectivity to any other multicoated optic i have. They certainly do not look like some sort of green dye has been applied as some i have seen do, rather the effect is on the subtle side, but plain to see if a fluorescent fixture's refelction is examined for example. Speaking of the fluorescent tube lights, I feel they work nicely as an aid to examine the construction of the lens system; if one looks closely one can actually see, using the innately linear nature of the reflection of the fluorescent tubes, the relative curvature of the lenses in it's reflection.
Full 80mm clear aperture. I might add these are *not* triplets (which i am thankful for actually). There are only two primary reflections visible from the objective end and one much smaller secondary reflection from the prism, identical in pattern & order to other doublet binoculars i have. If there was another lens element, there would be third primary reflection.
I examined the exit pupil with a 7x magnifying loupe. It measures 4mm and is not obstructed by the prisms or any other component in any physical way whatsoever--perfectly round. (This was in contrast to the Japanese Bushnell Rangemasters which exhibited heavy dimming in a square pattern within the exit pupil). Just for kix I also examined an image of the USAF chart as displayed within the exit pupil (also using the magnifying loupe) and noted even light across the field, no distortion until 90% out when mild pincushion set in and centerfield sharpness was maintained to 90% out, almost the very verge of the pupil. (This was *not* reflected in actual use as i'll get to in a moment--but I wonder why the exit pupil image would be flatter and display less distortion than the image seen in actual use is??)
I had only a half hour or so of clear sky for astronomical testing but the quarter Moon was well-placed and I wanted to make sure these binos performed well enough to hold on to before too much time went by.
I set them up on a tripod with a Manfrotto fluid head. The 25km crater Ross was chosen as a test object. It subtended an angle across it's diameter of ~12.7"arc at this point in the Moon's orbit (1792"arc diameter at time of observation, 1.94km:1"arc). The image of this crater essentially reduces to a pair of black crescents on a white background separated at their greatest extent by ~12.7"arc. When these crescents merge, it's image no longer is identifiable as a craterform. This represents apparant resolution of about 254"arc. The optics demonstrated they were capable of finer resolution however; as crater Sosigenes at 18km/9.76"arc was also [i]just[/i] discernable as a craterform (intermittantly during seeing), representing apparant resolution of just over 180"arc. (Incidently, this crater's diameter is misrepresented in Rukl's in case anyone checks.) I should also note the seeing was such that continuous image distortion was visible even at this low magnification so... I make the assumption that point source resolution would be slightly better than that obtained on these extended targets and that under better seeing there would also be a further albeit marginal improvement in resolution obtained on extended objects.
As for sharpness/focus across the field, i found that crater Ross remained resolved out to about one Moon width (1/2degree) from the edge of both sides of the field. That leaves about a three degree corrected FOV (see below re; FOV) Clouds forced me to conclude the tests at this point.
Overall, I am quite satisfied by the resolution these binoculars deliver.
Field of View:
The FOV of these binoculars is actually marked on them as 212ft/1000yards which is ~4degrees and not 189ft as advertised. 212/1000 would equate to an 80degree AFOV of the eyelens. Indeed the view is quite "immersive", reminiscent of the extent of view I get using the 30mm/80degree AFOV 2" ep in my refractor. Frankly I am looking forward to getting under a really dark sky with these--i anticipate the 'wow' factor will be significant! I did not have a chance to precisely measure the FOV using star fields, but got a good idea that it is at least close to accurate judging from the star field it showed in relation to Arcturus--it encompaassed Arcturus and went beyond 22 Bootes approximately the distance between it and the next brightest star in the "L" shaped asterism back towards Arcturus. Anyway, that is closer to 4 degrees than 3.5.
Collimation is not an issue. The images merge instantly, no problems there at all. I did not bother to peel back the rubber cover to look for collimation screws so whether or not it has any I don't know.
Field distortion (pincushion) is very noticable when viewing linear terrestrial objects in the outer 1/3 of the FOV but not really noticable when viewing the sky. In the short bit of sky scanning I didn't notice any 'rolling' effect in the moving image at all but rather the effect was quite smooth & pleasant. The same applied during daytime testing. This is rather subjective. I can say that compared to the 11degree fov of the Japanese 7x35's, the pincushion distortion in the 80mm's is *much* more evident.
The effects of chroma was plain in the image, manifesting as a rather narrow, yellowish border on the illuminated limb of the Moon. In daylight, electric lines backlit by the sky displayed a discernable purple fringe on one side and a yellow fringe on the other. This is I feel pretty typical--the Japanese binos did the same thing albeit not as plainly as the magnification is so much less. Stars appeared principally white save the brightest (-1 to 2mag or so) which exhibited chromatic color. In daylight I also took a look at the star-like reflection on a phone pole insulator. It appeared mostly white albeit brilliant with mild chroma and some flare; nothing spectacular.
I could detect no image rotation indicating astigmatism in the image of Arcturus between inside & outside focus.
I noted no obvious image ghosting at all.
I examined the interior of the binoculars using a strong beam of focused light. (giant maglite) The barrels are fully blackened and ridged. The paint is subpar; more reflective than I would like. There is a ring where the barrels join the body that, although black, is very reflective. I did test for image flare with the Moon just outside the edge of the field and must admit i found suprisingly little bleed over.
I naturally could not assess the light gathering ability of these binos nor deep sky contrast. I am certain they would prove deficient compared to fully multicoatd models. But, for the purposes I have in mind, (Messier hunting, purely recreational stargazing) I don't feel an extra 1/2 magnmitude or whatever is really essential or even worth doubling the price to get, at least not for me. :shrug: It's relative--if Jay Freeman was able to complete the Messier list using a MgF2 single coated pair of 7x50 widefields, I'm sure these Barska's will gather more than enough light/contrast for that sort of entertainment and much more.
The binos come with a semi-hard leatherette case with shoulder strap and a neckstrap for the bino's themselves. The lens covers are the snap-in type on the objectives (which fit tightly BTW) and a one piece cap for the eyelenses. However, in deference to the fragility of these binoculars, I set the case aside and got a 20$ hardcase with pluckfoam instead from Harbor Freight (the same as the Lowes cases). The binos fit securely and snugly inside along with a compact monopod. They come with a lifetime warranty against manufacturing defects with the usual exclusions and a 25$ handling fee.
To sum up I feel very satisfied as to the optical quality, thrilled by the ergonomics, somewhat underwhelmed by the mechanical quality and overall quite pleased. The mechanical fragility i have mentioned I don't consider to be a significant issue *for me* as i really baby instruments like this anyway. There are no mechanical deficiencies (that i can see) which I would anticipate becoming an issue, not just from the stresses of normal considerate & careful use anyway. Protected by the pluckfoam case I'd have no worries taking them down a jeep trail on a dual sport bike--as I have done often with my ETX-70 and intend to do with these as well.
If money were no object for everyone there would be no reason for binoculars like these to even exist. Such not being the case, (especially MY case!!) they fill a need. For 100$ one can enjoy a perfectly sevicable pair of binoculars which, if consistent care is taken in their use & storage, will doubtless give many years of that unique 'big bino' stargazing pleasure.
Comments, criticisms, etc always welcome.