20 X 80mm KonusVue

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The Konus 20 x 80mm KonusVue is a surprisingly able performer for such a reasonably-priced large aperture binocular. For about the price of many smaller and dimmer 8 x 42mm and 10 x 50mm binoculars, you get the immense light-gathering of two 80mm lenses (equal to two 3.1” rich field refractor telescopes, one for each eye). The KonusVue uses high light transmission BaK-4 prisms and fully-coated optics for bright images of faint deep space objects. Using two eyes to observe increases the resolution of small details by as much as 40% over the resolution visible when using only one eye when looking through a small rich field telescope.

While the KonusVue offers admirable astronomical viewing on its own, it also serves as a good wide-field observing complement to the narrower field of a telescope. You can get both a close-up view of a deep space object as well as a wide-angle view to put that object in context in the sky. With a reasonable 2.7° field of view, it excels at sweeping the star clouds of Sagittarius, searching out the Great Galaxy in Andromeda, taking in open clusters like the Beehive and the Wild Duck, and more. There is significant barrel distortion (straight lines away from the center of the field appear curved), but you very rarely observe straight lines in space and the effect is rarely noticeable. There is also some visible astigmatism and chromatic aberration at the edges of the field. However, these flaws are minor considering the binocular’s aperture and most observers (other than the most critical and nitpicky) will find them unobjectionable, particularly in view of the low price of the KonusVue.

The usable eye relief is quite good, at 14mm, although the image will vignette slightly for most eyeglass wearers. Soft rolldown eyecups shield the unaided eye from stray light when rolled up, and cushion eyeglass lenses when rolled down. The KonusVue has center focusing, like a conventional binocular, with a diopter adjustment ring on one eyepiece to match the binocular focus to your individual eyesight. With a close focus of 150 feet, it is not a general-purpose terrestrial binocular. That said, the KonusVue is a good choice for long distance terrestrial viewing under low light conditions. Nesting eagles or ducks across a lake at dusk are prime candidates for this big binocular. As a first serious astronomical observing tool, as a long distance nature study instrument, or as a highly useful companion to take into the field with your telescope at night, the Konus 20 x 80mm KonusVue is a very worthwhile balance of good performance versus low price.

The KonusVue binoculars use a molded polycarbonate body to keep the weight down below other 20 x 80mm binoculars, although the still weigh in at a stout 4.65 lbs (74.5 oz.) Using the binocular on a tripod is virtually mandatory, as few people will have the wrist strength needed to hold them steady enough for extended hand held use. For tripod use, a reinforcing bar runs from the prism housings to the objective lenses. In addition to providing structural rigidity that keeps the optics firmly collimated, it provides a sturdy support for the integrated photo tripod adapter. The tripod adapter can slide along the bar to balance the binocular on a tripod, no matter what part of the sky you are viewing. Once you find the correct balance, a large thumbscrew locks the adapter in place.

The binocular is fully clad in protective rubber armor. While the armor provides a more comfortable grip in cold weather, and protects the collimation of the optics against bumps and knocks, it does not make the binocular waterproof or fogproof.

The binocular comes with protective covers for the eyepieces and the objective lenses. The supplied woven neck strap is acceptable for occasional use. However, adding a wide heavily padded neck strap would be a comfortable addition if the binocular must be carried extended distances to an observing site. A lightweight hard carry case with carry strap completes the package.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
Field of view 1000 yards:
Exit Pupil:
The circular image or beam of light formed by the eyepiece of a telescope. To take full advantage of a scope's light-gathering capacity, the diameter of an eyepiece exit pupil should be no larger than the 7mm diameter of your eye's dark-adapted pupil, so that all of the light collected by the telescope enters your eye. (The eyepiece exit pupil diameter is found by dividing the eyepiece focal length by the telescope focal ratio.) Your eye's ability to dilate declines with increasing age (to a dark-adapted pupil of about 5mm by age 50 or so). For those in this age group, eyepieces with exit pupils larger than their eyes can dilate to simply waste their telescope's light-gathering capacity, as some of the scope's light will fall on their iris instead of entering their eye.
Relative Brightness:
A number used to compare the brightness of binoculars or spotting scopes of similar magnification. The relative brightness is determined by squaring the diameter of the exit pupil. The larger the relative brightness number, the brighter the image.
Twilight Factor:
A number used to compare the effectiveness of binoculars or spotting scopes used in low light. The twilight factor is found by multiplying the size of the objective lens (in mm) by the magnification and then finding the square root of that result. The larger the twilight factor, the more detail you can see in low light. A twilight factor of 17 or better if usually required for reasonable low light use.
Eye Relief:
Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

A note on our eye relief figures: Quite often, our eye relief figures will differ from those of the manufacturer. This is because we measure the “usable” eye relief, while the manufacturers specify their usually-longer (but technically correct) “designed” eye relief.

The eye lens of the eyepiece is normally recessed below the rubber eyeguard or rubber rim of the eyepiece to keep the lens from being scratched during use. An eyepiece might have a “designed” eye relief of 15mm (and the eye relief will truly measure 15mm from the eye lens to where the image forms). However, if the eye lens is recessed 3mm below the eye guard, the Ramsden Disk forms only 12mm above the eyepiece body (the 15mm “designed” eye relief, less the 3mm of eye relief made unusable by having the eye lens recessed into the body of the eyepiece). This “usable” eye relief of 12mm (measured from the rolled-down eyeguard – the closest point you can get your eye to the eye lens – to where the image forms) is the eye relief figure we would measure and list in this website.

Why is it important to list the “usable” eye relief? For those people who don’t wear eyeglasses while observing, a few mm difference between the eye relief they expect from the manufacturer’s literature and the shorter eye relief they actually get in real life doesn’t mean a lot. They can simply move a little closer to the eyepiece to see the full field, and never realize that the eye relief is a little shorter than they expected. However, some people must wear eyeglasses while observing, because of severe astigmatism. These observers can’t move closer to the eyepiece if the eye relief is shorter than expected because their glasses get in the way. For these people, the real life “usable” eye relief is more important than the technically correct but sometimes not fully usable “designed” eye relief. We measure and list the actual usable eye relief so that people in the real world can pick the eyepieces that will work best for them.

Interpupillary Distance:
Close Focus:
How close you can get to an object and still see a sharp image of it in your binocular or spotting scope is called the “close” or “near” focus
A binocular or spotting scope whose body is clad in rubber or polyurethane armor is said to be armored. Armor can be applied for looks, a better grip, noise-proofing, etc. An armored body does not guarantee that a binocular or spotting scope is waterproof, although most waterproof optics are armored.
The weight of this product.
4.65 lbs.
2 years
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  • Hard case with carry strap
  • Eyepiece and objective lens covers
  • Tripod adapter
  • Wide neck strap
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Konus - 20 X 80mm KonusVue

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Konus - 20 X 80mm KonusVue
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Our Product #: K2080
Manufacturer Product #: 2110
Price: $109.95  FREE ground shipping - Click for more info
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MSRP: $149.99

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This Konus 20 x 80mm binocular is a surprisingly good astronomical binocular at a very reasonable price. It gives you the light-gathering capacity of two 3.1” rich field telescopes for no more than the price of many smaller and dimmer 8 x 42mm or 10 x 50mm binoculars . . .

. . . our 34th year