Celestron's SkyMaster 20 x 80mm binocular is a surprising performer for such a reasonably-priced instrument. It is waterproof, something rarely found in a binocular in this aperture and price range. That means you don't have to worry about damaging the binocular if you set it down in dew-soaked grass after observing. Waterproof or not, however, we don't think we'd recommend fully submerging it in a puddle, or trying to use it in the rain. That might be tempting fate just a little too much. The Celestron 20 x 80 is covered in a light rubber armor that both provides a good grip when the binocular is damp from dew, and a comfortable grip when the weather turns chilly.
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. 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. The supplied lightly padded neck strap is acceptable for occasional use. However, adding a wide heavily padded neck strap such as the one listed below would be a comfortable addition if the binocular must be carried extended distances to an observing site. A lightly padded nylon carrying/storage case is standard equipment, as are protective eyepiece and lens caps.
The SkyMaster uses high light transmission BaK-4 prisms and multicoated optics for bright images of faint deep space objects. It offers the equivalent light gathering capacity of two 3.1" rich field refractor telescopes - one for each eye. 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, as you do when looking through the single barrel of a telescope or spotting scope. It offers admirable astronomical viewing on its own, as well as serving as a good wide-field observing complement to the narrower field of a telescope.
With a good 3.7° 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 some barrel distortion (straight lines at the edge of the field are curved), and some visible astigmatism and chromatic aberration at the edges of the field. However, these flaws are minor considering the SkyMaster's aperture and are unobtrusive for all but the most critical and nitpicky of observers.
Eye relief is specified at a very long 18mm. While this is technically correct, the actual usable eye relief typically measures a few mm less due to the recessing of the eyepieces when the eyecups are rolled down for eyeglass use. A shorter eye relief than specified is typical of all binoculars. There will be some minor vignetting of the field for those who must wear eyeglasses while observing.
Soft roll-down eyecups shield the unaided eye from stray light when rolled up, and cushion eyeglass lenses when rolled down. The SkyMaster is designed strictly as a long-distance observing tool from a tripod-mounted fixed location. With a close focus of 108 feet, it is not a general-purpose binocular. That said, the SkyMaster 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 Celestron 20 x 80mm SkyMaster is a very worthwhile balance of performance versus price.
