Telescope Reviews: Oberwerk 22x100 vs Celestron 25x100 Minireview

Oberwerk Giant 22x100 vs Celestron Skymaster 25x100

I had several months to use these binoculars. As far as the ability to see, 22x100s and 25x100s are a step above every 20x80 or smaller binocs I've used. Literally, they see more. They see fainter objects, and image scale is larger.

These binoculars are not perfect. I’ve seen slight flares in the image; I’ve seen a slightly bloated image in one or both sides of the binocular. Some are more difficult than others to bring to a fine pinpoint focus. Even with those deficiencies, these are the results achieved over a long period of months of use. Some have better coatings and contrast and certainly all are not equal in mechanical functions or quality of components. But what is most noticed is the dramatic increases in what can be seen with larger binoculars.

Mounting Considerations
If you've never seen or held or looked thru a pair of 100mm binoculars, when you first do get the chance, you will find these are dramatically different than anything else smaller you've used. These are big, real big. And they show it. They require a substantial mount, not just any tripod but a heavy-duty tripod with a heavy-duty head. Generally these binocs weigh about 8-10#. The best mount I have used for both of these binoculars is a sturdy Bogen 3246 tripod with a heavy duty Bogen 501 head. That setup will easily hold either of these 100mm binoculars.

The mounting post on the Celestron 25x100 is a polished chrome post without base plate. I found it difficult to keep it tightened against tripod mounting plate. In addition it deforms the rubber on the tripod mount plate.

The Oberwerk 22x100 has a black metal base plate which screws onto the bottom of the mount post. This makes a 1.5" diameter bottom contact area with the tripod mounting plate. It spreads out the area of connection to the tripod plate, eliminates the punching deformation of the rubber on the quick release shoe and it never once got loose.

Sharpness Across the Field of View
In the Celestron 25x100 sharpness of image is still good at 70% out from center, but then it drops off pretty quickly beyond 70%. By 80% out it gets rather poor. The Celestron has a problem with one side of the binoc that won't allow it to reach pinpoint focus as well as the other side.

In my sample of the Oberwerk 22x100, an unusual result is found. The best image sharpness is not centered in the lens. In order to see it, sharpness needs to be tested across the lens at various hour lines on a clock. Then it becomes obvious. Along one hour line, sharpness is OK to 70%, poor by 80%. But on the opposite side, it's sharp to only 40-50% and poor by 60%. Testing other hour lines shows the sharp central point is off-axis.

When observing a 14" double, the Celestron 25x100 was very clear at 50%, still good at 60% but poor at 70%, all the way around. Same double in the Obie 22x100, on one side was good to 60-70% and poor at 80%, but on the opposite side of the same barrel was good to only 40% out and poor by 50-60% out.

Differences Noted in the Coatings.
Actually the coatings on the Celestron appear like they might be single coated MgF eye lenses and prisms. Looking at light reflected inside the Oberwerk 22x100 shows a green reflection off the prism face towards the objective. The same in the Celestron 25x100 shows a light blue reflection off the prism face. Both had objective coatings that appeared purple/green with very little reflection off the objective lens.

Limiting Magnitude
Under my best skies ranging from mag 5.4 to 5.8;
20x80 Oberwerk Standard see stars to a limit of mag 11.2,
22x100 Oberwerk is capable of seeing stars as faint as 11.8,
25x100 Celestron could reach nearly to stars at mag 12.0.

Both the 100mm binoculars lost about a half magnitude in the area beyond 50% out from center. In most binoculars, losses grow to about a full magnitude as you move further out in the view.

Double Star Resolution
In 25x100s, Doubles of 7.1" and 7.4" are clearly separated. Mesartim at 7.8" is a successful target. Gamma Delphinus at 9.6" becomes an easy target. The Trapezium, with closest components at 8.7”, provides none of the difficulty associated with 20x80s.

I woke up early one morning and Aries was high in the southern sky, so I gave Mesartim a try. These Celestron 25x100 do not reach a perfect pinpoint focus on one side and that hampered the view somewhat. I was easily able to see the two components, but they were not clearly separated. The position angle was evident and there were two distinct bright components, but I could not see any solid space between them. I would say they were deeply notched.

I went out another morning with a 22x100 Oberwerk to try Mesartim. This time I saw a clean split. Difficult, but clean. Two nice little points with the tiniest of black space between them.

But for me the best I could do with the 22x100s was 7.8” for an apparent separation of 7.8x22 = 172 arcseconds. With the 25x100s I got 7.1” for an apparent separation of 178 arcseconds. With BT100s, successful doubles were 7.1 at 24x = 170 arcseconds, and 6.6 at 31x for 204 arcseconds. I have no eyepiece combinations for the BT between 31x and 25x. With the Fujinon 16x70, I have seen Gamma Delphinus 9.6” split at 16x for an apparent separation of 154 arcseconds.

Field of View
The Celestron Skymaster 25x100 binocular is advertised as 3.0°. It measures 2.45°.

The Oberwerk 22x100 is advertised as 2.8°. It actually measures Tfov at 2.7°.
They are still stamped on the prism housing as 3.5°, an artifact I presume left over from the fact that these binoculars use the older 20x80 Deluxe housing.

Both are still larger Tfov than the Pentax 20x60 (2.2°).
The Oberwerk 20x80 Standard is advertised as 3.5°. It measures 3.2°.

Chromatic Aberration
In the Oberwerk 22x100, Jupiter on-axis has very little CA, off-axis has moderate blue to one side. CA on the moon was a thin band and it was easy to move my eye placement to make it go away.

In the Celestron 25x100, Saturn produced no CA at all. None Seen in Venus on-axis, but blue and sometimes a purple or green was seen off-axis. Very little CA is seen on Jupiter out to about 50-60% from center. Beyond that, Jupiter produces blue CA on the inside edge and yellow/green on the outer edge. CA on the moon was green towards the outer edge.

With Jupiter at the very edge of the FOV in the 22x100s, CA is a pronounced red/ purple on the side towards the center of the lens. At the edge of the 25x100s, Jupiter produces a blue CA on the side towards center.

What Can be Seen
Fainter galaxies seem to be easy pickings for these 100mm binoculars. While M66 is seen bright, and M65 is difficult in the 16x70s, both are readily seen in the 25x100s. In addition, NGC 3628, the companion to M65/M66, not seen by me in any smaller binocular, was visible several times in the 25x100. M105 and its companion NGC 3384 make a nice pair.

M101 was found instantly in the 25x100, it was seen equally well in the 22x100, but on the same night it was only suspected in the 16x70s.

In the area just south of M11, oc M26 is seen easy in the 16x70 Fujinon, but nearby gc 6712 and oc 6664 are not seen at all. In 20x80 Oberwerk Standards, 6712 is seen and in 6664 only 3 or 4 stars can be glimpsed. In both the 22x100s and 25x100s, 6712 is seen readily and 8-10 stars can be counted directly in 6664.

Some few objects are so huge that they will not fit into the small field of view of these high powered binoculars. The Hyades is too large. Even the Pleaides is just a little too large to be viewed in context, but the amazing depth provided by the 22x100 and 25x100 binocs allows seeing about 200 stars in this cluster.

In the 22x100s, NGC 6934 in Delphinus was an obvious globular cluster. It was just seen in 16x70s. The 22x100 caught glimpses of another globular in Delphinus, NGC 7006. NGC 7006 was not seen in any binocular smaller than 22x100.

When you view faint clusters in 25x100s you see stars that just were not there in any smaller binocular. Star counts on clusters like IC4665 in Ophiuchus show 51* in the 25x100, 50* in the 22x100, but only 40* in the 16x70.

Oberwerk 22x100s and Celestron 25x100s make M12, a globular cluster, look like it is on the verge of resolution in the outer edges, where the Fujinon 16x70s could not resolve M12 at all. The Oberwerk BT100, using a 17mm Orion Sirius plossl at 36x did in fact provide some resolution in the outer edges of M12.

Illumination of the Exit Pupil
Celestron Skymaster 25x100
Light entering at 70% out on objective radius fully illuminates only the central 40% diameter of the exit pupil.
The central 20% of the exit pupil receives no light at all from the outer edge of the objective.

Oberwerk Giant 22x100
Light is off-center in both objectives. Light from the center of the objective does not produce the maximum exit pupil.
Light at 70% out on the objective radius, on one side of center, illuminates 80% of the exit pupil. With the light source on the opposite side of center, no point in the exit pupil is fully illuminated and the central 20% diameter of the exit pupil gets no light at all. On average, the central 40% of the exit pupil receives no light at all from the outer edge of the objective.

As a comparison
Oberwerk BT100 with 26mm TV plossl eyepieces at 24x
Light entering at 70% out on the radius of the objective lens illuminates the central 64% of the diameter of the exit pupil.
Light entering at 100% out, at the very edge of the field stop illuminates the central 10% of the diameter of the exit pupil.

Optical and Mechanical Deficiencies
I had some problems with the Celestron 25x100, that the left eyepiece would not achieve a pinpoint star focus, overall the view was very good, but the view thru the left eye was noticeably enlarged. This indicates some problem. Had these been a purchase, I would have sent them back as defective. I thought the exterior construction around the prism housings was a bit chintzy, not what I would have expected in a $300 binocular. The center mounting post was simply too short. I could not mount these binoculars on any tripod without the bottom of the barrels rubbing against the top of the tripod mount plate. If I were a person with a very narrow inter-pupilary distance, I would not have been able to achieve anything less than about 60mm with the currently supplied mounting post. There is no way to take that post off the binocular and replace it.

The Oberwerk 22x100 uses the body from the older model 20x80 Deluxe. Instead of dew shields screwed onto the front end, the extension is now part of the binocular body and the objective lens is moved out about 3” further. The 22x100, just like the old discontinued 20x80 Deluxe has a right diopter adjustment that seems set incorrectly at the factory. I use my corrective glasses with all my binoculars. Therefore, with many binoculars, the right eye diopter is set on or near zero. With the 22x100, it is almost at the very end of the minus diopter range. Like the older 20x80 deluxe, I could not use these binoculars without my glasses if I wanted to.

The illumination of the exit pupil test on the Oberwerk 22x100s shows an unusual result for this sample. This off-center illumination is, in my opinion, a substantial reason to consider this sample unacceptable. However, at this time I know of possibly only a handful of people besides myself who would ever perform such a test to find this anomaly. Maybe this is a good case for “ignorance is bliss”, because I was still able to see an awful lot of good stuff with both these binoculars.

Are these 100mm binoculars worth it?
Keep in mind a binocular allows you to see with both eyes. A 100mm binocular has two 100mm apertures with a combined area of aperture equal to a 141mm scope. Binocular summation allows the eyes to provide information to the brain that is greater than what would be seen with one eye in one of those apertures. Depending on the type of objects observed, that summation will range from 1.2x for light gathering to 1.4x for contrast beyond what is seen in a single 100mm aperture.

I really do agree whole-heartedly that a larger glass won't completely compensate for a mediocre design. However, I've put three different pair of 100mm binoculars up against the 16x70 Fujinons and Oberwerk 20x80s. The fact is, even with each of the 100mm binoculars with some optical deficiencies, the Fujinons could not see as much as any of the 100mm binoculars. 22x100, 25x100 and variable power BT100s see so much more than the 16x70 Fujinons that in some cases it's like seeing it small in the 16x70s and then finally adding enough magnification to really see it.

22x or 25x100 will not allow you to resolve globulars, but 25x100 with a 2.5° fov and a 4mm exit pupil will show you many faint nebulae, galaxies and clusters. 25x100s show nearby companion NGC galaxy to M95/M96 and to M65/M66, where the 16x70s do not (in my mag 5.4 skies. I suspect if skies were mag 6, the 16x70s would show the NGCs). 22x100s and 25x100s made M12 look like it was on the verge of resolution in the outer edges, where the Fujinons could not. The BT100 at 36x did in fact provide some resolution in the outer edges of M12.
The number of fainter stars seen in open clusters with both of the 100mm binoculars is greater than the number seen with the 16x70s or 20x80s. Using BT100s with 36x eyepieces, the number of stars seen and the faintest magnitude reached increases dramatically over both of the other 100mm binoculars.

Of course everything needs to be taken into context. I have no doubt the Fujinon 16x70 reaches the finest pinpoint sharpness and resolution. I haven't found a binocular to beat it. Maybe the 12x50 Nikon SE is in the same category. None of these fixed power 80mm or 100mm binocular bring stars to as crisply defined focus as the Fujinons. The contrast in the Fujinons may be closely equaled, but not beaten.

But, when it comes to how much can be seen, in just about every side-by-side viewing session, the larger binoculars saw more, and easily, not just barely. The 16x70s have a finer view, but the 22x100s and 25x100s will see more. If there are no optical deficiencies present that take away too much from the observation, then (even if you didn't add aperture) for most objects adding magnification allows you to see more.

Will I ever get rid of my 16x70 Fujinons in exchange for a 22x100 or 25x100. Not a chance. I haven't found another binocular that equals the quality of the Fujinons. But there is room on my equipment shelf for a 100mm binocular. A good sample of either one of these would make a good choice.

edz

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