Adler Optik Jupiter 20x80ZCF Giant Observation Binoculars Review

I previously owned two pairs of binoculars;

  • Super Zenith 10x50 7° field of view (handed down from my father, many years old, yet still nice view).
  • Fumoto 10x25

While both of these have served me well over the years, the Super Zenith 10x50's are suffering from a few knocks, and a fault which causes slightly astigmated views, and the 10x25's provide good images but are not particularly bright. So when asked what I would like for my birthday I decided that a new pair of binoculars would be very useful.

Here they are......

Adler Optik Jupiter 20x80 Giant Binoculars

We bought the binoculars from Scopes-n-Skies (click the link for the product page).

These binos are quite hefty at 2.7Kg, requiring tripod mount for stable viewing, and I also purchased at the same time the ScopeTeknix Zodiac ST90 counterbalance binocular mounting, which raises the binos right up to above eye level for comfortable viewing without having to strain your neck or bend down, and the counterbalance makes them easy to move around.

I would not recommend using these binoculars without a good tripod.

Sliding horizontal tripod attachment point

The bino is equipped with a central stabilising bar which is a heavy-duty horizontal tripod mounting point making it a simple matter to attach these binoculars to any photo-tripod (no additional mounting bracket required). The sliding mounting point can be positioned anywhere on the full length tripod mounting rail to allow the binocular to be balanced in the best, most comfortable position for the user when fixed to the tripod, or a counterbalance.

I have really come to appreciate how valuable a decent tripod is to increasing the viewing enjoyment through binoculars. No more acheing/shaking arms and wobbly stars, just plenty of time, relaxed and controlled, to view and concentrate on a particular area of the night sky. Very important for letting your eyes adjust when trying to discern dim stars, galaxies and nebulae.

In use, the only fault with the sliding mount point is that the nylon cylinder bush can allow the binos to swivel around the rod, and sometimes this can cause the bino body to be off-horizontal, i.e. one eyepiece becomes higher than the other. Really this is a minor point, and tightening the mount point knob a little further holds it a bit more firmly.

Focusing Adjustment

The Centre-Wheel focusing mechanism is quite stiff to adjust with the rubberised knurled thumbwheel, but this may be due to the type of grease used in the focuser and this might loosen up with use. This is probably not too much of a problem for astronomy work because you would generally focus on or near to infinity, and once set leave it, so a degree of stiffness may be an advantage to prevent defocusing.

Also I noticed some play when focusing in or out, where about a 1/16th turn of the thumbwheel is required when reversing direction before it takes up the slack and refocuses in the opposite direction. I am not sure how this might compare with other more expensive large observation binoculars. In practice this is only marginably noticeable when focusing, but a little annoying nonetheless.

Diopter Scale

The right eyepiece has individual focusing adjustment (also quite stiff to adjust, but likewise may be an advantage to prevent accidental defocusing).

Focus the binocular using the left eye (close right eye), then using right eye (left eye now closed), rotate the right eyepiece to focus with the right eye. Once both eyes have been carefully focused so the object is sharp and clear, the Diopter Scale allows you to take note of the setting for later easy resetting back to your vision requirements when sharing the binocular with someone else.

Although there is a white "alignment dot" on the static lens focuser, the raised Plus, Minus and Zero marks on the rubberised eyecup are very difficult to see in the dark even with a torch.

20x Magnification

One of the first things I pointed the binos at was Jupiter. At 20x magnification Jupiter is clearly a disc, and its bands can not really be made out due to its brightness, whereas my XT10i telescope provides sufficient magnification to view the planet details properly. However what the binos offer that you don't appreciate as much in the scope is to enable you to see the planet in its "wide-field" context with its moons orbiting, and the surrounding background starfield. Now that is something else.

The view thru the binos is wonderfully clear and bright, and with both eyes being used (instead of just one as with the telescope eyepiece), there is almost a 3-dimensional feel to the image. I really got a sense of the stars being distant, while Jupiter and its moons felt like they were suspended in mid-field. Quite stunning.

Detail on the Moon is very good, with craters at the terminator being clearly visible. The 3.2° field of view provides a very nice wide view, and the Moon occupies just over a third of the field of view.

80mm Aperture Objective Lenses

Next I pointed the binos more overhead and into the gems in the region of Cassiopeia, where the stars were beautiful bright sharp points of light, and I appreciated just how much the extra magnification and the larger 80mm aperture of the objective lenses really pulled in so much more light than my 10x50's and provided an awesome view of the Milky Way. Again the view felt almost 3-D and was very immersive.

The objective lenses have large individual and quite substantial rubber dustcaps which push fit onto the lenses very snugly, and have a lip which actually soft-snaps into place so preventing the dustcap from falling off. A reassuring amount of force is required to remove or fit the dustcaps.

IPD Scale

The IPD Scale (Inter Pupillary Distance) has 3 dots which can be used to note the position of the scale once you have found your desired setting to obtain a single circle field of view through both eyes. Again this adjustment is also very stiff, but likewise if you are the main or only user of the binos, you won't want this adjustment to change easily.

Internal Baffling

There appears to be fine internal-baffling to reduce reflections; the interior of the objective lens tubes is painted matt black, and appears to have fine ridging, machined into the metal along the entire length of the tube. On the few occasions I have used the binos to view the Moon there has been no obvious internal reflections.

BaK-4 Glass Porro Prisms

At the time Scopes-n-Skies were doing a special offer, so the binos cost a very reasonable £89.99 (normal price £179.99!). I noticed that there was another seemingly identical pair of Konus 20x80 binos for exactly the same £89.99 price (normal price £129.99), and on closer inspection discovered the subtle difference was that the Konus use porro prisms made of Bk-7 glass with full anti-reflection coatings on all air-glass surfaces, whereas the Adler Optik Jupiters use BaK-4 glass, which is superior quality, and hence what you would be paying the extra £50 for. So even though I preferred the look of the Konus, when it comes to the brighter and sharper image provided by the Bak-4 glass, it was a no brainer decision considering the identical discounted price.

The quality of glass used in prisms and how finely it is ground can affect the sharpness of images. The two more common types are BK7 and BAK4. Generally, BAK4 is more expensive, but considered better than BK7 for several reasons. One such reason is that BAK4 gives a nice round exit pupil while BK7 can produce distortion around the edge of the exit pupil as seen in the diagram (see reference article).

Again the binos do not appear to suffer from internal reflections which the coatings are intended to prevent, and viewing bright objects like the Moon there is very little chromatic aberration (prisms and lenses can often introduce false colouration to bright objects, i.e. white light is divided into its spectral components and this causes a slight rainbow effect).

Eyepieces and Eyecups

The large comfortable eyepieces have soft fold-down rubber eyecups making the binocular effective and comfortable for spectacle wearers. In use I find the rubber eyecups perhaps a little too flat for my liking, and when folded down there can be a tendency for any stray light from the sides to distract you. Even with the eyecups extended unless you press your eyes right against the eyecups this still occurs, and it might have been nice if the eyepieces were equipped with angled eyecups instead.


The eyepiece dust-cap is a single rubberised cover which fits over both eyepieces together, and can be attached to the neck strap. This means it is impossible to lose the eyepiece dustcap, which could occur if instead it was individual clip-on dust caps.

Fully waterproof

The body is rubber clad for ergonomic handling and robust protection and resistence to knocks and jolts. The binocular is fully water-proof, and will apparently float also (although I'm simply going to take the manufacturers word for this!).


The binoculars come complete with a neck strap, basic instructions, a sturdy carrying case with adjustable length shoulder-strap, an interior back pocket, and velcro securing strap to hold the binoculars firmly inside the case. The Scopes-n-Skies deal also included a free book; Stargazing with Binoculars, a well written, fully illustrated, 208 page guide by Robin Scagell - normally £7.99 and FREE with this binocular. Although in fact the book sent with my order was Stargazing With A Telescope, also by the same author.

The September 2008 issue of Sky At Night magazine reviews six pairs of 20x80 binoculars in a group test. One of them is a Visionary 20x80HD (£169.99) which is almost identical to my Adler Optik Jupiter 20x80ZCF, I am sure it is just badged differently with a green rubberised section around the eyepieces sporting a "V" for Visionary symbol, but probably comes from the same factory.

Anyway the Visionary was runner up with a Highly Commended 89% score. Here follows an excerpt from the Visionary review:-

"The lenses appeared multicoated but the internal barrels appeared shiny in places. That said, there was only slight evidence of internal reflections or ghosting of bright objects when we looked at the Moon and bright stars. Special mention has to be made of the front lens caps - they were rubber and fitted snugly inside the front of the lens hoods, unlike virtually all of the others on test, which slid over the outside of the front lens housing. The 3.2°-wide field of view was pretty good and sharp across 75% of the view, only trailing off slightly towards the edges. The star Albireo was colourful and displayed good contrast between its orange and sky blue components, while Mizar was cleanly split. M27, The Dumbbell Nebula, was bright with a box-like shape and the smaller Ring Nebula, M57, was a distinct smudge against the backdrop of stars. Turning to the only planet on view, Jupiter was adequate but did seem to have a slightly greenish tint to its disc. The galaxy M51 showed up as two smudges, one slightly larger than the other. Overall then these binoculars performed almost as well as the more expensive ones on review."

Later in the summing up section they say this (I have included the Winner of the test also for your interest):-

"...this left two contenders, and it was the balancing of many subtle points that led to the Visionary 20x80 HD taking the runner-up spot. We were really impressed with their great value, good optical quality and the front rubber lens caps. But the winner is the Monk Optics Observer 20x80 (£295). We liked the fact that internal reflections and ghosting of bright objects were kept down to a minimum. It showed that just as much attention to detail has been paid to the internal construction of the binoculars as to the optics. They performed brilliantly on all aspects of the night sky, making them worthy winners of this months Group Test."

After reading the Sky at Night Group Test I felt quite pleased with my original choice of AO Jupiter binoculars from Scopes-n-Skies, especially considering the massive discount they offered, yet offering good quality optics.


  • Objective lens diameter: 80 mm
  • Magnification: 20x
  • Brightness: 16.0
  • Field of view: 52m @ 1000m (~3.2°)
  • Close-focus: 13m
  • Dimensions: 340 x 100 x 227mm
  • Weight: 2.7kg

Stability for Viewing

With binoculars of this size, they are quite heavy and suitable methods of supporting them is a must. Not only will your arms buckle under the weight after a while, but they just cannot hold the binos steady enough, and stars will just be a constant blurry motion.

While a good sturdy Tripod is the simplest method, why not consider one of the following alternatives, from the sublime to the ridiculous! While all of these are homemade chairs, a couple of them will supply the chairs as kits for purchase.

Thanks goes to Walt Reil at Central Coast Astronomical Society for the above fascinating links.