Celestron’s SkyMaster 20-100 x 70mm zoom binocular gives you very high power observing for very little cash. The 70mm SkyMaster zoom uses high transmission BaK-4 prisms and multicoated optics for surprisingly bright images of faint deep space objects. It has the light-gathering capacity of two 2.75” refractor telescopes – one for each eye – so you effectively gather as much of the light of faint deep space object light as a 3.88” diameter refractor.
In addition, using two eyes to observe increases the resolution of small details by as much as 40% over the resolution you perceive when you use only one eye, as you do when looking through the single eyepiece of a telescope or spotting scope. Observing comfort is also improved when using both eyes to observe naturally, since you don’t have to constantly squint to keep one eye shut as you do when using a telescope.
Zooming from a high power 20x magnification to a really high power 100x takes only a flick of the thumb on the power change lever on the right eyepiece. The field of view is 1.25° at 20x, making the SkyMaster zoom very useful for examining globular clusters and the smaller nebulas. At 100x, the field drops to 0.25° across, so that the Moon more than fills the field of view, with surprising amounts of crater and rille detail visible in an almost three-dimensional display. Surprising amounts of detail are visible when observing the planets at the higher end of the magnification range, as well.
A tripod adapter is included with the Celestron 70mm zoom for mounting the binocular on a photo tripod or binocular parallelogram mount, as it is almost impossible to successfully hand hold this binocular. Combine the 53 ounce weight with the 20x to 100x magnification of this Celestron, and using a tripod to support the binocular is mandatory if you want clear, shake-free views. Few people will have the wrist strength needed to hold it steady enough for extended hand-held use. Successfully hand-holding this high power Celestron is not in the cards.
The supplied lightly padded 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 lightly padded nylon carrying/storage case is standard equipment, as are protective eyepiece and lens caps.
The Celestron SkyMaster 70mm zoom is weather resistant, but not waterproof. It is covered in 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.
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.
Soft roll-down eyecups shield the unaided eye from stray light when rolled up, and cushion eyeglass lenses when rolled down. Eye relief is specified at 22mm, for unvignetted views for those who must wear eyeglasses while observing. While 22mm 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, although this is generally not enough to vignette the view for eyeglass wearers. A shorter eye relief than specified is typical of virtually all binoculars. A diopter adjustment ring on the right eyepiece lets you match the binocular optics to your own individual eyesight.
The SkyMaster is designed strictly as a long-distance observing tool from a tripod-mounted fixed location. With a close focus of 72 feet and a narrow 1.25° field of view, the SkyMaster zoom is not a general-purpose binocular. That said, the SkyMaster is a good choice for long distance terrestrial viewing under low light conditions, as well as astronomy. 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 20-100 x 70mm SkyMaster is a worthwhile balance of high power performance versus a very affordable price.