20-100 X 70mm SkyMaster zoom

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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.

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.
3.5mm @ 20x
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.
12.25 @ 20x
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.
37.42 @ 20x
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.
53 oz.
Limited Lifetime
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1. Raymond on 4/30/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I am a retiree who has had an interest in astronomy since the third grade. I have had a variety of Telescopes and binoculars and when some of the neighbor children began taking an interest in the moon and stars, I decided to take out my Dependable Celestron Skymaster for an evening with my neighbors 9 and 12 year old. Mounted on a sturdy camera tripod and with the space station scheduled to go over our part of the South (Nashville) we zeroed in on the March Sky. After a brief orientation three neighborhood kids took turns looking at the moon, and various stars. The Celestron Skymaster 20/100x70 zoom proved the perfect introduction to the wonders of the universe.
The added attraction of skylab arcing over our area and the ability to vary the zoom provided an outstanding evening. The Celestron Skymaster needs a sturdy tripod as it too heavy for long term viewing and stability is important. The ability to utilize both eyes provide a much larger aperture to observe and the optics from Celestron are always fantastic. I recommend the Skymaster as a great general purpose set of optics for both casual viewing and to narrow your search and progressing to your main scope. The Skymaster is a great value and a great addition to my collection. ye ole grouch
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Celestron - 20-100 X 70mm SkyMaster zoom

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Celestron - 20-100 X 70mm SkyMaster zoom
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Our Product #: C70Z
Manufacturer Product #: 71012
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Clear skies,

Celestron’s SkyMaster 20-100 x 70mm zoom binocular has nearly the same light gathering capacity as a 4” refractor for very high power lunar, planetary, and globular cluster exploring at a very attractive price . . .

. . . our 38th year