8X56mm SkyMaster DX

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This Celestron 8 x 56mm SkyMaster DX has a wide 5.8° field and a very bright 7mm exit pupil. These virtues make it ideal for serious wide field astronomical viewing. You can sweep the star clouds of Sagittarius, search out the Great Galaxy M31 in Andromeda and the Pinwheel Galaxy M33 in Triangulum, and revel in globular clusters like M13 and M22. The SkyMaster DX uses high light transmission BaK-4 prisms and fully multicoated optics for bright images of faint deep space objects, particularly from a truly dark sky observing site. While it offers quite nice astronomical viewing on its own, it also makes a good wide-field observing complement to the narrower field of a telescope.

The optical performance is surprisingly good, particularly in view of its large aperture and very sensible price. The optics are fully multicoated on all air-to-glass surfaces for high light transmission. The field of view is respectably flat. Astigmatism, distortion, and chromatic aberration at the edges of the field are well controlled. This makes for clean and expansive views of open clusters like the Beehive and the Wild Duck, with point-like stars to the edges of the field, as well as fascinating sights like the Double Cluster in Perseus.

At 38 ounces, the SkyMaster DX is rather heavy. We recommend using it on a camera tripod for the sharpest images, as few people will have the wrist strength needed to hold it steady for extended hand-held use. A 1/4”-20 thread mounting hole for an optional photo tripod adapter (#1185) is built into the SkyMaster’s center hinge, hidden under the removable Celestron logo.

The body is armored in black rubber for a comfortable grip and added protection against unexpected bumps and thumps. Because it is O-ring sealed and nitrogen-purged to be waterproof and internally fogproof, there’s no need to worry about putting the binocular down in dew-soaked grass or letting dew bead up on it during an evening’s observing session. The large ribbed rubber focusing wheel is easy to adjust, even when wearing gloves. P>Eye relief is specified at a very long 18mm. Unlike many binoculars, whose actual eye relief typically measures less than that specified, the SkyMaster DX truly has a full 18mm of usable eye relief. It’s a refreshing change from the overly optimistic figures quoted by many manufacturers. Rubber-rimmed twist-up eyecups shield the unaided eye from stray light when up, and cushion eyeglass lenses when down.

One and a third turns of the large focus knob moves from a not-so-close 25’ near focus out to the far reaches of the Universe. With a 25’ close focus, this center-focusing Z-body SkyMaster DX is obviously not designed for close-in nature study. That said, its very bright images and good resolution will do a creditable job of revealing small details from what would normally be considered an excessively distant vantage point. It is a good choice for long distance terrestrial viewing under low light conditions. The 8 x 56mm is excellent for revealing underwing field markings of raptors in flight, for observing deer feeding in distant meadows early in the morning, or any other twilight birding or nature study activity where close focus is not required – but bright images are essential. 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 8 x 56mm SkyMaster DX is a very worthwhile balance of performance versus price. The SkyMaster DX comes with a wide and comfortable woven neck strap, a soft vinyl case, an eyepiece rainguard, and objective lens covers.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
5.8°
Field of view 1000 yards:
304'
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.
7mm
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.
49
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.
21.17
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.

18mm
Interpupillary Distance:
58-72mm
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
25'
Height:
7"
Armored:
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.
Yes
Waterproof:
Yes
Weight:
The weight of this product.
38 oz.
Warranty:
Limited Lifetime
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  • Neck strap
  • Soft case
  • Eyepiece rainguard
  • Objective lens covers
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Celestron - 8X56mm SkyMaster

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Celestron - 8X56mm SkyMaster
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Our Product #: C856SM
Manufacturer Product #: 72022
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The Celestron 8 x 56mm SkyMaster DX is an ideal tool for astronomical viewing. While it offers bright and sharp celestial views on its own for spur-of-the-moment observing, it also makes a good wide-field observing complement to the narrower field of a telescope . . .





. . . our 34th year