An Odyssey of Three Oberwerk Binoculars for Astronomical Viewing

An Odyssey of Three Oberwerk Binoculars for Astronomical Viewing

(User Review – July 2024)

Introduction:

In June of 2024, I purchased three different models of Oberwerks’s straight-through binoculars and two tripods/heads exclusively for astronomical viewing.  I delved into amateur astronomy six years ago and regularly use a 6” Schmidt Cassegrain Telescope (SCT named Starling) on an equatorial mount and 12” Dobsonian reflector (named Big Bertha) with a wide array of eyepieces and other accouterments.  Because I am a visual observer and do no astrophotography, I really enjoy manual navigation using charts or setting circles for altitude/azimuth, rather than automated go-to devices.  This has allowed me to gain a familiarity of the sky that lends itself exceptionally well to astronomical bino viewing.  I had been looking at the Oberwerk line of products, along with other brands, for several years before I purchased them:  delaying gratification, doing research, and attempting to dissuade myself of a large purchase usually prevents buyer’s remorse.  To pre-empt my conclusion, I have zero remorse.

Why did I choose these binoculars at this point in my astronomy odyssey, rather than a larger Dobsonian or a refractor?  Prior to purchasing the Oberwerks, I had one pair of binoculars I use for general viewing and target location to assist navigation with my telescopes – Athlon Midas G2 UHD 12x50’s.  They are a light weight, roof prism rig with hard, helical eyecups and excellent optical performance.  I could not ask for more out of them.  However, there is a performance gap between them and the lowest power that I can achieve with the SCT with an f6.3 reducer at 30x (47x without the reducer), and 40x with the Dobsonian. Having an array of Oberwerk 15x70s, 20x65s and 25x100s with enhanced apertures over the standard 50mm apertures nicely fills this gap without duplicating telescope equipment with redundant optical performance.  Additionally, the versatility of binos with their portability, rapid deployment capability, compactness compared to telescopes, and ability for terrestrial viewing expand my options significantly over another telescope.

Why did I choose these large straight-through binoculars versus a model among the large binocular telescopes (BT70XL-ED – BT127XL-SD) with 45° eyepieces?  As nice as they appear, their apertures (i.e. light gathering ability) and magnification ranges fall well within the parameters of my telescopes.  I would not gain any optical enhancement or increase in performance over my telescopes, particularly for the price.  However, as stated above, the straight-through versions do serve a role unfulfilled by my telescopes.  That said, if you are new to astronomy or wish to relegate your sky viewing to one instrument (good luck avoiding the optics fever, for which there is no vaccine), then I would highly discourage your choice of straight-throughs and recommend you explore your options among the large BT models with various eyepieces.  There is no “one best” optical instrument for all people for any given application.  Determine your intentions and budget and chose accordingly.  When considering straight-through binoculars for astronomy with fixed magnifications, think of choices and attributes like crime scene photography:  8x42s and 10x50s are appropriate for overall views, 12x50s and 15/16x70s are appropriate for intermediate views and  the 20x80s and 25x100s are appropriate for close-ups.

Oberwek 20x65 ED Deluxe

Review based on 12+ hours use June-July 2024, between the hours 2100-0300 in a semi-rural residential location, Arkansas, temperature 78°- 88° humidity 50% - 80%, daytime heat index 103° - 112°, transparency ranged from poor to very good:

Optical Perception:

First light was not a good impression or introduction to these binos.  I set up the rig and began viewing within minutes. The moon was approximately 40% and waning gibbous. The sky was cloudless, but as I determined, far from transparent.  Views of the moon exhibited prominent color aberration in blue along the entire limb of the moon and I was unable to achieve satisfactory focus of any stars.  The entire session was a wash.  I did not panic. I believed they had been collimated as certified and questioned if it was an alignment issue enroute via UPS as the box arrived upside down because the bottom tape came undone. The next session as weather permitted yielded much different results with no action taken.  The primary difference was I now allowed the binos to set outside and acclimatize to ambient conditions with a fan for 20-30 minutes prior to use, just like a telescope. There is a significant enough difference between a climate controlled house and the heat/humidity of summer evenings in the Mid-South to warrant acclimatization. That plus more favorable transparency demonstrated the acute results that can be achieved with these binos.  I continued to test them through full moon into new moon phase.  The full moon, even low on the horizon with atmospheric dispersion, exhibited no color aberration and provided most satisfying clarity of view and sharp detail.  I was able to achieve near pinpoint clarity on dimmer stars while 0 – 2nd magnitude stars were well focused but tended to exhibit diffraction spikes.  As stars are perceived as points of light and many are at similar distances, viewing is almost par focal.  I found myself making few minor adjustments to focus throughout a session unless viewing planets or the moon.  There is excellent color preservation with absolutely no purple or violet fringing.  While the perception of the B-V color rating of stars is relative to individual physiology and eyesight, I found the hues of rated red/yellow giants, and carbon stars to be rich, consistent with my telescopic viewing experience and appropriate in color representation for expected classification.

The ability to individually focus each eye piece is a plus for me as I have one near and one far eye and the diopter range of +/-5 is more than ample.  My only issue with these binos is the supplied eye cups – flared rubber that can be folded back.  I wear glasses, but never when using binos or a telescope.  My best fit is to nestle the eye piece into my eye socket and rest my brow bone on the top rim of the eye piece – become one with the optical train.  The cups do not readily permit that and Oberwerk offers no alternatives with which to retro-fit.  Therefore, I circumcised the flared extensions, leaving a thin rubber band around the metal rim.  I then circumcised the straight neck portion from the cut-off flared section and stretched that over the metal rim as well for extra cushion…..more better, by a lot for me.  Your preferences and eye relief may differ.  Perhaps several of those thick blue rubber bands that hold the broccoli bunches together would be the ticket?  I find the hard plastic, helical twist up/down cups on my Athlons to be the ideal arrangement.  If Oberwerk paired those with the individually focused eye pieces on the 20x65s I could rightly call it a world class binocular.

Magnification/Aperture:

I quickly grew fond of the 20x magnification eyepiece to the 65mm objective ratio in its output of 3.2° actual field of view.  My Athlon 12x50s provide a 5.4° field of view with good contrast and perception of brighter nebulae.  However, knowing how much more lay just beyond this threshold left me begging for more horse power to go deeper.  The 20x65s really stepped up to the task in which magnification, aperture and contrast all contributed to pulling out objects that are imperceptible in the 12x50s:  globular clusters M54 (circa 88,000 light years – small, puffy and non-stellar), M69, M70, M80, M107, and one of my favorite juxtaposed views – NGC 6441(circa 38,000 - 44,000 light years) just a frog hop from G Scorpii (circa 150 light years). What a pair:  a brilliant yellow giant in our galactic front yard next to a globular cluster whose simmering glow is seen through the gas and dust of the Milkyway’s bulge from the ‘back of beyond.’  The 20x65s performed well on all the common double stars and preserved their colors well.  β Scorpii is a six star system in which two are visible to the amateur eye, separated by approximately 13.5 arc seconds.  I could clearly split these with a very small amount of clear space between them. Struve 2816 in the Elephant Trunk Nebula (IC 1396) is a multiple star system in which the primary and next most visible companion are separated by about 12.5 arc seconds. I could clearly split them with a sliver of dead space betwixt them.  Therefore, I interpolate my limit (eyesight + optics) between 10 and 12 arc seconds separation before doubles turn into snowmen or become imperceptible as doubles. I viewed Saturn between 0200 and 0300 awaiting its climb along the ecliptic to improve the view.  Although its rings are nearly edge-on currently I could clearly detect the ring plane as a needle bisecting the globe with some radius and space between the rings and planet on one side.  Titan was also readily visible.  That said, the view was minimal and merely used as a testing measure.  There was no detail or aesthetic satisfaction in the view due to limiting factors of magnification and not quality of the optics.  Bear in mind age, physiology/eyesight and the ever changing atmospheric conditions are factors that determine how closely you can achieve the theoretically optimum performance of any given optics.

A thought on actual field of view:   some folks like binoculars in the 8x42 or 10x50 range for the expansive field of view they offer.  The greater the actual field of view, the lower the magnification.  Conversely, the higher the magnification, the narrower the actual field of view.  How narrow is too narrow?  That is a personal preference.  By comparison the largest actual field of view with my 6” SCT and array of 1.25” eye pieces I have is 1.7° with the f6.3 reducer and 1.1° without it.  The greatest actual field of view with my 12” Dobsonian and 2” eye pieces is 1.8°.  Now, how generous does the 20x65s 3.2° field look?  Even the 25x100s 2.63° actual field of view is significantly larger than what my telescopes offer.  It is all in perspective.

Contrast:

The isolation of light tempered with the muting of the ambient sky/background is excellent.  This somewhat enhanced the view of the Andromeda galaxy (2.5 million light years.), insofar as its structure is perceptible in the range of the human eye spectrum, and the smudge of the Sombrero Galaxy (28 million light years).  Good contrast additionally enhanced the overall diffused light of various globular clusters and the M27 Dumbbell and M57 Ring planetary nebulae (puffy, torus shape with central space imperceptible) and added some perceptible structure to the Eagle, Swan, Trifid and Lagoon nebulae over views with the 12x50s, 15x70s, and some telescope views.

Navigation:

Upon receipt of binos I used them for several hours sans any pointer/navigation aids before installing a multi-reticle red dot finder.  At 15” long on an alt/az mount they are akin to small tandem refractor telescopes.  Sighting down the center and finessing windage/elevation is largely doable, but highly inefficient, inaccurate and plain aggravating.  I installed the picatinny rail and ring mount offered by Oberwerk.  Caveat:  this device is available on Amazon and is intended for installation on a 1” shotgun barrel. It is not tailored for these binos.  Most, if not all picatinny rail/mount hardware has been devised by the firearms industry for firearms optics and adapted to certain astronomical viewing applications.  Creativity rules here.  The horizontal center post of the 20x65s is 0.875” per my calipers.  The inside diameter of the picatinny ring mount is 1”.  Fortuitously I had some surplus black rubber hose from a dishwasher I recently replaced that had the perfect inside/outside diameter to serve as a compression spacer.  I favor the red dot finder offered by Agena and have used it on my telescopes for years as well, with much satisfaction.  Now all my red dot finders are consistent among all my optics and utilize the same CR2032 battery.  My enjoyment of the binos increased measurably after using the red dot finder to expeditiously and accurately navigate to desired targets without sweeping the stars from the sky.  Additionally, the finder serves as a reverse location tool.  If you are generally viewing the sky and locate an unknown, noteworthy target, center it in the field of view, lock the alt/az axes on the head and look through the finder to where the red dot is projected onto the sky.  You can then use star charts or planetarium software to identify the target.  Such reverse orientation also improves your skills of manual navigation immensely. I cannot imagine using binos this size without a finder.

Tripod/Head:

I went with Oberwerk’s recommended 4000 tripod with the 5000 head and dual panning handles.  The head is rated for a 10lb capacity, which efficiently accommodates the 6.6lb binos.  As with any mounted optics, you want to leave a margin between rated capacity and actual weight, rather than max out a mount’s limit.  This ensures stability, quicker vibration dampening, and smoother movement.  I initially loosened all locks and tensioner and readily found the balance point of the binos and tightened them to the head plate.  The 4000/5000 combo is a perfect rig for these binos without being too much or too little mount, and at a commensurately good price for what you get.  I found the altitude/azimuth motions, tensioner, and locks to work consistently well thus far and they are easy to manipulate by feel in the dark.  I use the altitude lock the most and like the ergonomics of the star knob.  I found it best to extend the tripod legs to full length, level with built-in bubble, and minimize extended height of vertical riser, although it holds very well.  Vibration dampening takes a couple extra seconds naturally, the higher the vertical riser is raised.  I leave the binos on the tripod/head most of the time and occasionally exchange them for the 15x70 Ultras.  If you intend to use multiple binos on one mount, I recommend a dedicated quick change plate for each pair.

Addendum on star charts:  there are a number of star charts tailored for use with binoculars and small telescopes.  Those new to bino astronomy would benefit by avoiding more extensive charts at this point in the journey that will contain extraneous information accessible only to higher horse power optics. Three commendable resources are:  Night Watch by Terrence Dickinson and Ken Hewitt-White; Observer’s Sky Atlas by Erich Karokschka; and the Sky & Telescope Pocket Sky Atlas.  As has been rightly said, the real joy of astronomy is only realized with the knowledge you bring to the eye piece.   Stars take on a new shine when you understand stellar life cycles and the views of open and globular clusters, planetary, emission and reflection nebulae and galaxies become a more meaningful experience when paired with professional photos and research information.  What an awesome time to be an amateur astronomer with the wealth of information available to augment your viewing sessions.

Oberwerk 25x100 ED Ultra

Review based on 7.5 hours use June-July 2024, between the hours 2100-0300 in a semi-rural residential location, Arkansas, temperature 78° - 88° humidity 50% - 80%, daytime heat index 103° - 112°, transparency ranged from poor to very good:

Optical Perception/Contrast:

Ironically and most notably my subjective impression of the field of view was and remained more expansive and immersive at 2.63° than that of the 20x65s at 3.2° and the 12x50s at 5.4°.  The sense of being interjected into the star fields was immediate, especially with open clusters, which made for aesthetically enjoyable viewing for entire multi-hour sessions (hence, the popularity of refractors).  As expected with an additional 35mm of aperture and 5x magnification over the 20x65s, the contrast and definition of reflection nebulae was somewhat improved on the Eagle, Swan, Trifid and Lagoon nebulae, but not significantly.  Likewise the planetary nebulae M27 and M57 were slightly larger and mildly more defined with the central void slightly perceptible in M57.  Where I noticed an objectively measurable difference over the 20x65s was the marked enhancement of globular clusters and especially open clusters in size, intensity and depth.  As stars are perceived as points of light and many are at similar distances, viewing is almost par focal.  I found myself making few minor adjustments to focus throughout a session unless viewing planets or the moon.  Similarly to the 20x65s, there is excellent color preservation with absolutely no purple or violet fringing.  While the perception of the B-V color rating of stars is relative to individual physiology and eyesight, I found the hues of rated red/yellow giants, carbon stars to be rich, consistent with my telescopic viewing experience and appropriate in color representation for expected star classification.

Magnification/Aperture:

The increase in overall visibility and density of field stars as well as clusters is a function of the 100mm aperture and not the 5x magnification increase over the 20x65s.  Bear in mind magnification does not make light brighter or more perceptible, but aperture (i.e. light gathering capability) does…..and how, with these.  The magnification to aperture ratio with these is very well balanced, akin to tandem, low power refractor telescopes.  I would not want the magnification any higher, thereby reducing the actual field of view and immersive feeling.  Globular clusters were somewhat larger with markedly brighter nuclei and halos and more defined over the 20x65s with M4 and M22 going from fuzzy/hazy to mottled and grainy with some stars resolved on the periphery.  The notoriously obscured M71 globular cluster in Sagitta, (13,000 light years), commonly mistaken as an open cluster, was nicely drawn out and sufficiently defined to contemplate globularity.  I tested the 25x100s on all the same double/multiple star systems as the 20x65s with similar clarity, color preservation and ability to separate components.  The extra 5x magnification created a miniscule increase in separation distance, but not significantly.  I found my limit splitting doubles with γ Delphini (8.9 arc seconds) and ξ Cephei (8.1 arc seconds).  Therefore, I interpolate resolvability to 8 arc seconds (my eyesight + optics).  Thus, I found a minute increase over the 20x65s on doubles.  That said. The 25x100s appreciably excelled at an immersive, more star rich, brighter view over the 20x65s, especially with open clusters.  Similarly as a test measure, I observed Saturn between 0200-0230.  The view was sharp, brighter and more defined than the 20x65s with a brilliant globe transversed by a well defined, but undetailed ring structure with some dead space between the radius and globe.  Titan appeared largely the same as with the 20x65s.  Outside a few very faint globular clusters (NGC 6522, 6528 in Sagittarius and a somewhat enhanced M54 (87,000 light years), I could not find any notable targets or objects with the 25x100s that I could not find with the 20x65s.  To reiterate: the extra 35mm of aperture results in the greatest viewing difference and advantage (light capture), rather than the 5x magnification. As a result I almost felt like I was falling head first into the Sagittarius star cloud and M11 and its environs exploded into a panorama more pleasing even than viewing with my 12” telescope due to a field of view twice as large.

The ability to individually focus each eye piece is a plus for me as I have one near and one far eye and the diopter range of +/-5 is more than ample.  My only issue with these binos is the supplied eye cups.  I like the fact they are low profile and favor them over the extended, flared cups of the 20x65s.  The low profile rim can be folded back.  Mine are stiff and were prone to snapping back to their extended position unprovoked.  This happened several times while I was viewing, creating an unexpected and offensive impact to my eye and head jerk reaction.  I wear glasses, but never when using binos or a telescope.  My best fit is to nestle the eye piece into my eye socket and almost rest my brow bone on the top rim of the eye piece – become one with the optical train.  The cups do not permit that and Oberwerk offers no alternatives with which to retro-fit.  Again, like the cups on the 20x65s, they seem to be the Achilles’ heel to otherwise high quality binoculars.  Guess I need more of those big blue broccoli rubber bands…..good thing I like broccoli.

Navigation:

I installed the same picatinny rail/ring mount as I did on the 20x65s .  The diameter of the short collar on the central bar of the 25x100s is 1” and required no improvisation or spacer for installation.  Likewise, I installed the same multi-reticle red dot finder (sourced from Agena). To prevent duplication, refer to my entry under the 20x65s.  At 3” longer than the 20x65s, I would not attempt to use the 25x100s without a finder or navigation aid.

Tripod/Head:

I went with Oberwerk’s 5000 tripod and upgraded to the Small Rig head with dual panning handles.  The head is rated for a 14lb capacity, which efficiently accommodates the 10.0lb binos.  As with any mounted optics, you want to leave a margin between rated capacity and actual weight, rather than max out a mount’s limit.  This ensures stability, quicker vibration dampening, and smoother movement.  I initially loosened all locks and tensioner and readily found the balance point of the binos and tightened them to the head plate.  The 5000/Small Rig combo is a perfect arrangement for these binos without being too much or too little mount, and at a commensurately good price for what you get.  I found the altitude/azimuth motions, tensioner, and locks to work consistently well thus far and they are easy to manipulate by feel in the dark.  I use the altitude lock the most.  Were I to split hairs, I favor the star knob on the 5000 head over the blade knob on the Small Rig altitude adjustment for ergonomics and quick tactile access.   I found it best to extend the tripod legs to near full length with the binos about 6” above my head height, level with built-in bubble, and minimize extended height of vertical riser with crank, although it holds very well.  Vibration dampening takes a little longer naturally, the higher the vertical riser is raised, especially at 10lbs.  I leave the binos on the tripod/head permanently as a dedicated rig.  While the 5000 and Small Rig heads can achieve 90° orientation for viewing targets near or at the zenith, it is not neither comfortable nor practical for any length of time with straight-throughs.  I am fit and active and like to stand at the tripod for 5 hours straight.  If you don’t or have limited mobility/flexibility, consider a parallelogram mount and an observing chair or zero gravity chair to accommodate the 15x70s, 20x65s or 25x100s for comfortable viewing near or at the zenith.  I am sure I will get there at some point and age.  Obviously this is where the BT versions with 45° or 90° oriented eye pieces on a fork mount excel.  What is the solution when viewing this constrained portion of the sky with a tripod mount?  Stay up longer until the area crosses the zenith and attains a manageable viewing angle toward the Western horizon whilst still in that zone of minimal atmospheric influence.  I did not find it onerous to wait for M13 et alia, in order to beogle their spangled orbs and attendant nebulous wonders.

Oberwerk 15x70 Ultra

Review based on 5.5 hours use July 2024, between the hours 2100-0300 in a semi-rural residential location, Arkansas, temperature 78° - 88° humidity 50% - 80%, daytime heat index 103° - 112°, transparency ranged from poor to very good:

Optical Perception/Contrast:

About 7-10 days after I received these, the Oberwerk website withdrew their availability and announced the arrival of the ED version soon.  I found allowing these to acclimatize to ambient conditions/temperature beneficial, but required significantly less time than the 20x65s and 25x100s, thus permitting more immediate use and ability to achieve optimum focus sooner.  Views were crisp with sharp focus almost to the edges.  However, I have never had any field of view in my telescopes or the 20x65s and 25x100s that were  as ‘tack sharp’ at field edge as at the central region.  I do not know what that means and I do not expect to based on the physics of optics and my aging eyes.  If I want a sharp target, I move it to center.  I found one major advantage of the 15x70s over the 20x65s and 25x100s to be their ability to tone down the diffraction spikes of 0 – 2^nd magnitude stars, a function of the reduced magnification.  Bright stars and stellar giants were better defined as a result and aesthetically more enjoyable to view.  If I were to go on a safari for giants, (Antares, Arcturus, Vega, Altair, Kochab, Enif, Sirius, Rigel, Aldeberan, Betelguese, etc.), these would be my first choice of caliber.  Bear in mind lower magnification is better suited to viewing stars, whereas higher magnification is desirable to split double/multiple stars and of course define detail with planets and the moon.  With general star viewing less is more.  Color preservation was good and largely comparable with the 20x65s and 25x100s, though perhaps minutely different in hues, presumably attributed to the absence of ED glass.  However, all perceived colors were well within the B-V rating parameters of what I would expect.  I experienced no purple/violet fringing or halos.  Contrast with nebulae and the gaseous Milkway bulge was decent, more on par with the 12x50s and a little less prominent and defined than the 20x65s and 25x100s.

The eye cups resemble those on the 25x100s with a low profile rim that can be folded back.  They proved adequate folded down, but not deserving of high marks in fitment to face and comfort.  Early-on in the session one of the cups spontaneously unfolded, slapping me in the eye, as with the others.  Perhaps this may be partly attributed to the temperature of the rubber cups in which cooler temps in the house cause them to be less malleable and flexible and exposure to the heat outdoors causes them to remain folded down.  If so, that does not bode well for winter viewing conditions.

Magnification/Aperture:

Allow me to prefix this section by saying if I were pressed to assemble a bino package for astronomy use, and I were constrained by cost, manageability, portability and performance, I would get a light weight, quality pair of 10x50s or 12x50s with magnesium housing for handheld applications and a quality 15x70 or 16x70 pair on a mount.  That combination of optics with their ratios of magnification to actual field of view and light gathering capacity would aptly satisfy the majority of what can be achieved with binocular astronomy, without missing out on too many deep sky objects and quality of experience within the reach of larger binos.  Whilst that combo will not put you on the bench at the fifty yard line, it will put you far from a top row seat in the galactic stadium.

Starting on the macro scale I examined two sets of visual trios with the 12x50s and the 15x70s:  Alcor and Mizar (82-86 light years) with Mizar’s visible companion separated by 14.4 arc seconds, and Omicron¹ in Cygnus (750 light years) with its A and C components separated by 1.8 arc minutes.  Under seeing conditions at the time I could not detect Mizar’s companion nor the Omicron¹ C component with the 12x50s, but did so readily with the 15x70s.  I tested the 15x70s on many of the wider, popular doubles (δ Cephei, Albeiro, 61 Cygni, β and ζ Lyrae, etc.) with excellent resolution of separation and color.  Moving up to tighter doubles to compare with performance of the 20x65s, I examined β Scorpii and the two primarily visible components of Struve 2816 in IC 1396 near μ Cephei.  Both required concentration in order to just detect the smaller component, giving both a snowman appearance with no discernible space or separation between them.  An unfamiliar or casual observer would have swept over them as a single star, while η Cassopiae at 13.4 arc seconds lay just beyond resolvability. Therefore, I interpolate my limit (eyesight + optics) circa 14 arc seconds.  Incidentally, the 15x70s did μ Cephei (Hershel’s Garnet star) complete color justice in all its glowering beauty, making the contemplation of its estimated titanic size all the more enjoyable.  Turning to the globular clusters, the bright, popular ones (M4, M13, M15, M22, etc.) appeared well formed with a discernible brighter core and hazy halo, but all remained fuzzy with no approach to graininess or detailed resolution on periphery.  Some of the more intermediate globular clusters (M19, M28 and M62) readily revealed their globular nature as fainter, hazier orbs.  Taking up the challenge of the fainter conglomerates, M80 was just discernible as a puffy star with no real definition.  Again a casual observer would likely miss it entirely.  And NGC 6441 near G Scorpii was only discernible as a fleeting ghost with averted vision because I knew where to look.  Star fields and open clusters were nicely arrayed in the 4.4° field of view, and yet did not come close to rivaling the experience with the narrower 25x100s on open clusters and star fields:  the 15x70s made me feel like an observer and the 25x100s a participant.  Nevertheless, the 15x70s present a near perfect magnification to aperture ratio and produced a very satisfying night of viewing.  I foresee many a night using no more than these accompanied by my 12x50s.

Navigation:

The design of these binos do not permit direct attachment of a red dot finder.  Navigation with them by winging elevation and windage and sighting down the middle over the top is moderately accurate and the 4.4° actual field of view gives a little larger ball park for desired targets to fall within.  I find these 15x70s to be the transition point in size where you can reasonably use them without a finder, or benefit by installing one without it being overkill.  I tend to modify stuff.  I will likely attach a multi-reticle red dot finder.  I find attaching the L bracket to the rear of the plate provides a good balance point and leaves sufficient real estate to the front of the plate to fabricate and attach a short extension to support a Synta style dove tail mount with riser and/or picatinny rail system for a red dot finder.

Tripod/Head:

I use these interchangeably with my 20x65s on the 4000 tripod with 5000 head, to which they attach to the head plate with the included L adapter.  The tripod and head (10lb capacity) are an ideal combination that is neither too much nor too little mount for steady and smooth operation with these 5.5lb binos.  I ordered an additional quick change plate so each pair of binoculars has a dedicated plate affixed to it with its respective balance point established, which precludes the necessity to readjust with exchanges on various Oberwerk mounts.  I found fully extending the tripod legs put the horizontally oriented binos 3” – 4” above my head.  The L adapter adds a little extra height as the binos rest higher off the mount/plate than the 20x65s and 25x100s.  Once tilted back the eye pieces met my eyes at about the right height for 45° - 65° viewing angle. This reduced the amount of riser required which resulted in virtually no vibration or dampening period.  I found it quick and easy to adjust the riser to accommodate shallow or steeper viewing angles, with no slop or slippage.

Conclusion:

I reiterate: I have zero buyer’s remorse after ruminating on these binos and having used them thus far to the extent reported.  I expect their service life to exceed mine.  I understood their functions and limitations well before purchasing. They have greatly enhanced my astronomical viewing and filled a niche falling below the magnification thresholds of my telescopes, but with a significantly expanded actual field of view, while still providing significant magnification levels above my 12x50s.  While there are other high quality brand binoculars available, most are tailored for “sport” use and affordability/variety peaks around the 15x56 size.  I do not know of any other brand that currently offers binos in the 15x – 25 x ranges with apertures up to 100mm with the features, quality, product support, customer service and price that Oberwerk offers.

My greatest discontent with the binos is the eye cups on the 20x65 and 25x100 models.  While this may seem trivial, it is an issue with significant implications as eye relief, facial fitment to the binos and a comfortable experience for hours on-end is crucial to achieving proper focus and desire to utilize the binos.  Eye cups are where the rubber meets the viewer, where the viewer meets the optical train and gets onboard with the instrument.  My experience with the eye cups was not commensurate with the quality and experience I had with the binos and tripods/heads. They are a feature that deserves the attention of Oberwerk similar to its attention to collimation.  I would like to see Oberwerk rework these eyecups or offer interchangeable options to accommodate a wide variety of needs and preferences.  One size hardly fits all here.  If you wouldn’t walk a mile in shoes two sizes too big or small, why battle ill fitting eye cups for hours?

The 20x65 (15” long) and 25x100 (18” long) models are not quite like smaller sport versions that you throw up to your face and readily change focus point with instant results.  If you approach them more like telescopes, permit acclimatization to ambient temps and conditions and are patient to initially focus them, they will produce sharp, rich, color correct views that are nigh impossible to improve upon for the instruments they are.  The 25x100 has more telescope DNA than binocular DNA and represents the transition point at which binos really become telescopes.  They are a choice for the experienced to step up to, not for a beginner to start with.  As with any new hobby, less is more until you learn what “more” means.  I made my foray into astronomy with an inexpensive 4” reflector to figure out if I wanted to go bigger and deeper.  And yet, I still made mistakes later on with the purchase of eye pieces in particular before fully learning what “more” meant:  festina lente – make haste slowly.

Disclaimer:  I have no history with Oberwerk or familiarity with its owner or employees.  I have received no special consideration or remuneration for this review.  I am a fully paying, first-time customer.

morgan a.

Arkansas - 35° N latitude

(Dew point during the duration of testing hovered around +/-73° and night time temperatures never attained the dew point level.  Temperatures during testing were somewhat elevated over annual norms. Thus, I cannot address dew formation, particularly on the 100mm objectives.  However, I am fabricating a set of light shields to double as dew shields for the 25x100s).