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Oberwerk 45-deg 100mm Binocular Telescope

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Untitled Document OBERWERK 45° 100mm TELESCOPE BINOCULAR

I have been an amateur astronomer for over 40 years, during which time I’ve owned/used many instruments. About 5 years ago, I decided the time was right for me to step up to instruments with the best optics I could afford. To that end, I am fortunate to live in a northern suburb of Cincinnati, OH near a highly regarded optical designer and telescope maker – Richard Wessling. Dick built and supplied the primary mirror for my 15” f/5/5 Dob. Another telescope maker, John Pratt designed a great wheeled frame to interface this telescope with a Tom Osypowski dual-axis aluminum tracking platform… but that’s another story. Dick Wessling also designed and built my 10” f/6 Dob. Both of these telescopes are optically flawless and are very easy to use. I wanted to have the same experience with binocular viewing.

My quest for large format binoculars

In 1985 I purchased a pair of 15x 80mm Steiner binoculars. They always had what I considered to be an objectionable amount of color. In fact, using them on the moon would convince anyone that the moon actually was made of green cheese! However, they were mechanically sound, provided very sharp images across the field of view, and served me well for many years for low power wide field viewing.

In 2005, I attended the Apollo Rendezvous in Dayton, OH. Big Binoculars had an exhibit and I tried out several of their 100mm binoculars. I settled on a pair of Oberwerk 25/40x 100A binoculars. I really liked the versatility of being able to change magnification. While I was very, very pleased with their optical and mechanical performance, from the beginning, I found them difficult to use when mounted on the standard wood tripod, even with the 15° adapter. In keeping with Big Binocular’s reputation for unequaled customer support, Kevin offered to allow me to return the standard tripod and give full credit towards the Bogen 475 heavy duty tripod. However, the standard wood tripod was very sturdy even if it was inconvenient, and it was also too beautiful to part with. So, I elected to purchase the Bogen 475 tripod with a Bogen 501 head. This tripod/head combination proved to be much more convenient to use. However, it definitely was not as sturdy as the standard wood tripod. I would say the Bogen tripod and head were pushing the limits for support. For example, when raising or lowering the binoculars by using the center column, it was necessary to use one hand to support the binoculars. When at a group or public star party, I did worry that someone could knock over the binoculars. Finally, while the Bogen 575 was much more convenient than the standard wood tripod, it was still uncomfortable for me to observe at altitudes above 60 degrees.

Oberwerk 45° 100mm Binocular Telescope

I was never dissatisfied with the optical or mechanical performance of the Oberwerk 25/30x 100A binoculars. However, I still wanted a more convenient viewing experience. Early in 2006, I became aware of Oberwerk’s new 45° 100mm binocular telescope. This design allows the user to use the 1 1⁄4” eyepiece of his or her choosing, thus providing for a wide range of possible magnifications. The 45° prisms also make for very comfortable observing regardless of the altitude of the object being viewed. To top it off, these binoculars came with a fork mount. At $1795, these binoculars are not cheap. Once again, the Big Binocular customer support came through. Because I live only a 1-hour drive from the Big Binocular showroom, Kevin suggested I come in so he could examine my Oberwerk 25/45x 100A binoculars, and to give me a chance to try out the 45° BT 100 binoculars. For those of you who have never visited the Big Binocular showroom, it would be well worth a visit. I was able to try out many binocular/mount/tripod/eyepiece combinations to make sure I was totally satisfied with my final decision. Since my 25/45x 100A binoculars were in pristine condition, and were only 1 year old, Kevin offered me a very fair trade-in price which I gladly accepted.

Next, I had to decide on a tripod. The 45° BT 100 binoculars weigh a hefty 26 lbs. The fork mount adds about 10 lbs more. It takes some serious support to handle this much weight. I tried the 45° BT 100s on three tripods: the standard wood tripod, the Bogen/Manfrotto #475 heavy duty tripod, and the Bogen/Manfrotto #3258 very heavy duty tripod. There was no contest. The #3258 tripod was as solid as a rock and was without a doubt the hands down winner. Kevin then suggested I try an option I hadn’t considered: the Bogen/Manfrotto 3156 folding dolly. Not only did this provide even more stability, but we could effortlessly move the binoculars across any level surface (decks, parking lots, sidewalks, etc.). Although Bogen/Manfrotto makes an even heavier-duty dolly with 5” wheels (#3067), the #3156 dolly provided more than enough support for use on a level surface. I should note that the foot pedal release makes it a snap to release or engage the dolly’s wheels.

Optical and Mechanical Performance

I picked these binoculars up directly from the Big Binocular showroom. Together, Kevin and I checked out their performance. I was completely satisfied with everything, from the optical coatings and beautiful finish to every mechanical adjustment and the clear sharp images. However, these tests were performed in the daytime, and I was anxious to try them at night. I was not disappointed. As would be expected with any semi-apochromatic triplet objective there is some color. But, this was minimal and not objectionable. The only flaw in optical performance was noted with a pair of 9mm Type 6 Nagler eyepieces (67x): there was a very small flare apparent on the left side. The right side was deemed to be “perfect” by several observers with highly trained eyes. The flare on the left side was not apparent with a pair of Type 6 13mm Nagler eyepieces (46x). I contacted Kevin who offered to fix this. However, neither my wife nor I were bothered by the very small amount of flare, so we decided not to pursue it further. Recall that these binoculars replaced a pair of Oberwerk 25/40 100A binoculars. There never was any concern about optical performance. The views of the moon, comets, deep sky objects and planetary conjunctions are everything you could hope for in a 100mm binocular. The issue for me was usability.

Usability: The ultimate binocular experience:

The fork-mounted 45° BT 100 binoculars sell for $1885, with the optional 7x50mm finder. The Bogen/Manfrotto #3258 tripod retails for $465, and the #3156 folding dolly adds another $178. This comes to $2528 – without considering the cost of additional eyepieces. By comparison, the 25/40 100A binoculars (with finder scope) cost $`1580. What kind of performance did I get for the nearly $1000 additional cost? I think it’s fair to say that this binocular/mount/tripod combination gives me the ultimate binocular viewing experience. First, the 45° BT 100 binoculars come with a wheeled case making it much easier to transport them. The fork mount is as sturdy as it is beautiful. In addition to being sturdy, the fork mount is very smooth. Moving the binoculars is a breeze. The fork mount dramatically outperforms the Bogen heavy duty 501 tripod head I used with the 25/40 100A binoculars. When you combine the fork mount with the 45° angled viewing, you just can’t find an uncomfortable viewing altitude!

I can’t over-emphasize the value of the Bogen/Manfrotto #3258 tripod. It is far, far sturdier than the standard Oberwerk tripod or the Bogen/Manfrotto 475 heavy duty tripod. It is easily as sturdy as the optional Oberwerk heavy duty surveyor tripod with spreader ($299). With a rated load capacity of 44 lbs., the #3258 can easily support the binoculars and fork mount. In addition to its sturdiness, the #3258 claim to fame is its enormous range of height adjustment (16.5 to 104inches). When the binoculars are mounted on a tripod it is very risky to adjust the leg height of the tripod. So, even if you are using a fork mount, you can experience inconvenient or uncomfortable viewing heights. This is particularly likely when several people are viewing. However, the Bogen/Manfrotto tripod has a beefy geared center column that easily allows you to raise or lower the viewing height. Thus, it is very easy to achieve and maintain optimum viewing height. This is priceless for extended viewing periods or when at a star party.

The Bogen #3156 folding dolly was an unexpected surprise. In a perfect world, you would set up your binoculars and that would be that. However, I’ve found it is often necessary to move the binoculars to obtain a better viewing location. If you are on a flat surface, this dolly lets you simply roll the binoculars to a new location. A convenient foot pedal lets you engage/disengage the wheels. The dolly also folds easily for storage and transportation. Even when I’m on a lawn or other “rough” surface and don’t anticipate moving the binoculars, I usually choose to use the dolly. The tripod/dolly combination all but eliminates worries that someone could bump into the binoculars and knock them over. (Since my tripod is the black version, I also attach red LEDs to each leg when I’m observing with other people.)

Finally, the whole point of a binocular telescope is to be able to use interchangeable eyepieces. I’ve added 13 and 9mm type 6 Nagler eyepieces to the 24mm eyepieces that came with the binoculars. I doubt that I’ll want to add any eyepieces that would give higher magnification, but I’m toying with the idea of getting a pair of 40mm eyepieces for very low power (15x) viewing. Eyepieces are such a personal preference, I do not feel the need to address the issue further other than to say it is great to be able to choose my desired magnification/fov/eye relief, etc.

OK – what about the cons? Basically, the only thing which interferes with the viewing experience is the weight of the system. The binoculars weigh 26 lbs; the fork mount weighs 10 lbs; the tripod weighs 18 lbs; and the dolly weighs 10 lbs. With my Steiner 15x80 binoculars, I could leave them set up on the tripod and carry them outside in an instant. That’s not possible (at least it’s very inadvisable) with the Oberwerk 45° BT 100 binoculars. Furthermore, while the binoculars fit very smoothly into the fork mount, I find it much safer to make this a two-person operation. Since my wife is also my observing partner, this is not a problem for me, but it could be for someone else. Make sure you can handle these before you purchase them.

I find the 7x50 finder to be of limited use for astronomical purposes. I will probably see if I can get a holder bracket for my green laser pointer that will fit into the mounting holes for the finder bracket. I wish that Oberwerk would offer a fitted aluminum hard case for the binoculars. The standard wheeled case is convenient for every day use, but I’m not sure it’s sturdy enough for airline use. I also wish they would offer a case for the fork mount.


The Oberwerk 45° BT 100s are optically and mechanically excellent. The fork mount is superb. This unit is as great to look at, and look through as it is comfortable to use. The binocular/mount combination is heavy (36 lbs.) and demands heavy duty support. I would recommend nothing less than the Bogen/Manfrotto 3258 heavy duty tripod with a rated capacity of 44 lbs. This tripod has a geared center column that is beefy enough to support the binocular/fork mount. The combination of the 45° viewing angle, fork mount, geared center column and individually selectable eyepieces together with the 45° BT 100 optical and mechanical excellence interact to produce an unsurpassed binocular viewing experience.
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