Celestron SkyMaster Astronomical 25x100mm Giant Binocular

By Chuck Hawks

Celestron SkyMaster Astronomical 25x100mm Giant Binocular
Illustration courtesy of Celestron International.

Celestron has been marketing giant binoculars for many years. In the 1980's and 1990's, when I was working as the Manager of France Photo in Eugene, Oregon, we were a full line Celestron dealer and I developed a fondness for their giant binoculars. Like their telescopes, Celestron binoculars were well made, offered excellent optical quality and represented a lasting investment at a reasonable price, the mark of true value.

I have long wanted to review Celestron giants and my friends at Optics Planet (online at www.opticsplanet.com or call 800-504-5897) kindly provided the Celestron SkyMaster Astronomical 25x100mm binoculars featured in this review. They arrived packaged in an outer cardboard shipping container and inner decorative cardboard box. Inside the latter was a nylon binocular case specially designed for these giants.

This deluxe case is unusual, since it includes a fitted outer nylon cover with a flap protecting the access zipper and an inner padded case with Velcro closure. Unzip the outer cover and fold the top down, then open the "doors" of the inner padded box to remove the binocular, which is held securely in place by a Velcro strap. No need to remove the outer zipper cover to quickly access the binocular. This convenient case provides excellent protection for the giants and comes with a removable, over the shoulder, carrying strap. Another strap is provided for the binocular itself, but I cannot imagine wearing giant binoculars around my neck!

Inside the packaging, you will find a truly impressive binocular. They don't call the Celestron 25x100 a giant for nothing! It is physically imposing, measuring over 16 inches in length and weighing almost nine pounds. The huge, 100mm (nearly four inches across) multi-coated, dual objective elements get everyone's immediate attention. "Wow!" was the most common comment when someone saw them for the first time, even from the rather jaded members of the Guns and Shooting Online staff.

Here are some general features and specifications for the SkyMaster 25x100:

  • Item #71017
  • 25x magnification porro prism binocular (BAK-4 prisms)
  • Multi-coated optics
  • Enhanced structural reinforcement to the main binocular body
  • Protective rubber body covering
  • Waterproof
  • 100mm (3.94") objective lenses
  • Angular field of view - 3 degrees
  • Linear field of view - 157 feet at 1000 yards
  • Exit pupil - 4mm
  • Eye relief - 15mm (suitable for eyeglass wearers)
  • Minimum focusing distance - 80 feet
  • Individual eyepiece focus with rubber eyecups (the rubber eyecups can be folded back to accommodate eyeglass wearers)
  • Interpupillary Distance - 56mm (2.2") minimum, 72mm (2.83") maximum
  • Weight - 140 ounces (8.75 pounds)
  • Length - 41 cm (16.125")
  • Width - 26 cm (10.25")
  • Integral tripod adaptor rod
  • Deluxe padded nylon carrying case with strap
  • Lens caps included
  • Celestron Lifetime No Fault Warranty
  • 2009 MSRP $346.99

Celestron's Lifetime and No Fault warranty deserves comment. Celestron binoculars are warranted free of defects in workmanship and materials for the useable lifetime of the product and Celestron will repair or replace them for free. The No Fault provision means that regardless of how the binocular may have been damaged or destroyed, Celestron will repair or replace it without question for a nominal fee of $25. I know of no other company in the industry that offers this kind of warranty.

The sample SkyMaster 25x100's optical adjustments are smooth, but very tight. It takes considerable effort to turn the eyepieces to focus, making focusing laborious and imprecise. Adjusting the interpupillary distance requires what I would call excessive force and this makes it difficult to make the fine changes necessary to get it exactly right. The bottom line being that it is difficult to get this binocular set correctly for your eyes.

The Celestron Astronomical giant binoculars are provided with an integral tripod mounting system. There is a chrome-plated, .665 inch diameter rod fixed along the axis of the binocular. It is apparently threaded into the front (objective) brace and stabilized at the rear by a bracket with a tiny setscrew. The cylindrical tripod mounting foot slides back and forth on this bar and is tightened in place by a chrome-plated knob. Using pliers, I tightened the bar to the front brace as tight as I could get it and also torqued the rear set screw as much as I dared. This system is much better than the typical "L" bracket that attaches to the front of most binoculars and works fairly well for Celestron's smaller 15x80mm and 20x80mm giants, but it is insufficient for the size and weight of the 25x100mm SkyMaster.

Part of the problem is the small "foot" at the bottom of the binocular's tripod mount. Measuring only 1.3" in outside diameter, this simply lacks the requisite surface contact area to keep the giant binocular from "squirming" on the head of a tripod. It is an inadequate mounting surface. Tightening the 1/4x20 screw that attaches the binocular to the tripod with a pair of pliers helped, but did not solve, the problem. (Note: The Bogen 3057 I was using is a professional tripod head; do not use pliers to attach these binoculars to the head of a typical amateur tripod!)

Terrestrial Viewing

The Celestron giants can be mounted on a heavy-duty camera tripod for daylight terrestrial viewing. A "fluid" video head would be an asset here, to allow smooth aiming. I made due with Bogen #3035 tripod legs topped by a conventional #3057 head. This massive photo tripod is recommended for use with cameras up to 8x10 inch format. It is not a lightweight set-up; the binocular and tripod together weigh 22 pounds. This combination proved entirely adequate for terrestrial viewing, but inconvenient and marginal for astronomical viewing.

I live near the west bank of the Coast Fork of the Willamette River in Oregon. I tested the 25x100's daylight performance on some prominent objects visible from my yard and it was impressive. For instance, at a laser verified 51 yards I watched an ant climbing a neighbor's fence post as clearly as if it were right in front of me. At 216 yards, I could easily see the individual needles on the branches of a tall fir tree. At 582 yards, I could see the individual leaves on a distant oak tree. I could resolve the individual leaves on a maple tree at the top of a hill on the far side of the river, but I could not measure the range to that maple tree, because it is well beyond the 1000 yard maximum measuring distance of my Leupold rangefinder!

A birdwatcher operating from a fixed location would go nuts over these binoculars. They could also serve nicely to spot bullet holes in targets at a rifle range. However, being much larger, heavier and bulkier than a conventional spotting scope, few shooters would choose to drag them (and a heavy duty tripod) along for that limited purpose.

Astronomical Viewing

Celestron SkyMaster Astronomical binoculars are, as the name implies, especially convenient for observing (relatively) large swaths of the night sky. They are ideal for viewing large astronomical subjects, such as open clusters and star fields. They are very bright and you do not have to squint one eye to use them. The view through the 25x100 giants is correctly oriented, which makes "star hopping" to locate objects relatively easy.

The best mounting system I could manage for this review was the aforementioned Bogen #3035 tripod leg set with a Bogen Side Arm attached to the top of the tripod and a Bogen #3057 head attached to the business end of the Side Arm. The other end of the Side Arm can be counterbalanced to off-set the weight of the head and binocular by hanging some sort of weight from it, such as a jug of water (a gallon of water is about the same weight as these binoculars) or a small mushroom type boat anchor secured by a short length of nylon line. A heavy duty parallelogram mount would be ideal, but I didn't have one available.

The Side Arm allowed enough offset so that I could get under the binoculars to view the night sky and the three-section #3038 legs are tall enough to allow viewing from a standing position. I used the tripod's geared center column to make small height adjustments. In addition, the angle of the legs relative to the center column is adjustable, which is convenient for use in the field. Altogether, however, this is a heavy, cumbersome, inconvenient and expensive way to mount giant binoculars. Celestron could do their astronomical giant binocular customers a big favor by introducing a mount/tripod combination that is actually designed for use with these instruments.

Although it lacks slow motion controls, for the giant 25x100 binoculars this tripod system proved superior to the Celestron recommended Heavy Duty Alt-Azimuth Tripod. (There is a review of that tripod on the chuckhawks.com Photography and Astronomy page.) Unfortunately, this expensive and sophisticated Bogen tripod set-up is not something that the average person is likely to own; nor, for that matter, find in stock at most camera/video stores. In my case, it is left over from two decades spent as a professional, large format, photographer.

I found focusing the SkyMaster binocular at night difficult, as considerable force is required to turn the eyepieces and the eyes must be tight against the eyecups in order to see the full field of view through the binocular. All of this touching of the binocular induces movement that made whatever star I was trying to bring into focus jump around in the field of view. It is hard to focus on a jiggly point source of light.

I did manage to view a few common astronomical objects from the front yard of my mobile home. I live about 3.5 miles outside a small town in Oregon (population 4700). This is not a dark sky site, as every home has a light at the corner of their driveway. However, it is darker than a city residential area, because we do not have to contend with the immense sky glow.

First, I looked at the moon, which is impressive when viewed through the big SkyMasters. Lots of detail and, because the moon is a plane surface (rather than a point source of light), the apparent sharpness is good. Using both eyes is a definite advantage here compared to a telescope operating at the same 25x magnification. I was not bothered by color fringing or flare, although these did cause problems later when I viewed stars and planets.

Next, I viewed Jupiter. I should mention that the binocular's wide field of view made it relatively easy to find, and "star hop" to, objects in the night sky. It was easy to see all four of the giant planet's primary moons. I was not able to resolve any surface detail on Jupiter due to color fringing, flare caused by the planet's brightness and the jiggle blur caused by an inadequate mounting system. The lightest touch of a single finger would make the view shiver, even though I was using a very large tripod with a massive head. A conventional amateur photo tripod would be worthless with these binoculars. Both Jupiter and the moon were fairly low in the sky and therefore reasonably comfortable to look at.

After Jupiter, I looked at the famous "double double" in Lyra. (A pair of stars in which each of the "stars" is itself a binary pair.) Lyra was almost directly overhead and, while I was able to point the binocular straight up, it required some very uncomfortable neck craning to look through it, even with the Side Arm on the big Bogen tripod. To be practical for astronomy, binoculars would require star diagonals, just like telescopes. Some people with very sharp eyes claim to be able to split the main pair with the naked eye, but I have never been able to do that. With the Celestron Giants, it was absurdly easy to split the first pair. I could not split the second pair, however, even using my best averted imagination. I could almost see that they were binary stars, even if I could not actually split them. However, that is probably because I knew what they are supposed to look like, rather than any detail actually revealed by the binocular. I concluded that the 25x100's do not have quite enough magnification or resolution for splitting true binary stars.

The last object I looked at was the Ring Nebula. This deep sky object is the remains of a super-nova star that blew itself into what appears to be a neat smoke ring in space. It is also in the constellation Lyra and I was able to find it using averted vision. The Ring appeared as a tiny, dim patch. The binocular was not able show its unique ring configuration.

The real obstacle to astronomical viewing with the 25x100 giants is finding some sort of rigid mounting system, a problem I was not able to overcome for this review. The only practical solution would be a custom designed and built parallelogram mount, preferably on a permanent pier base. The binoculars themselves are impressive and I think that they would be great for the amateur astronomer if a sufficiently sturdy and convenient mounting system can be constructed.




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Copyright 2009, 2014 by Chuck Hawks. All rights reserved.


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