Oberwerk Ultra 15x70 Compared to other 70mm binoculars
by Ed Zarenski Oct. 15, 2006
Are These All the
Same? The buzz on the street is all about the new "premium"
binocular. There are a number of importers/distributors currently offering what
appears to be the same binocular. Keep in mind, none of these
importers/distributors actually make these binoculars. Oberwerk, Garrett, APM,
AP, General Hi-T, TS, AOE, they all import these binoculars, variously referred
to as Ultra, Grizzley, Marine, Premium, etc.
While there is no positive assurance that we have identified all the
originating sources, it is a pretty fair bet to say, there are not seven
different manufacturers of these binoculars.
Of course it is nearly impossible to tell if they are all "exactly" the
same. We know from experience that any particular model line can be custom made
for any distributor. As an example, over the last few years, one of the most
commonly available import binocular sizes on the market has been the 15x70. You
can pick up a low to mid-priced Barska, Celestron, Apogee, Oberwerk, Garrett,
Telescope Service (or some other brand name) and set them on a table next to
each other. At least for some of them, by looking at outward appearances you
could not tell one from the other. However, are they all the same? Well, often they are not.
We have identified probably as many as a half dozen different
things that can be done or not done during manufacture that could make all
these brands different. There is a post in the CN binocular forum "Best
Of" threads titled "These Look the Same, What Could Be
Different?" It addresses not only
things that you can readily see, but also some of the differences you cannot
see by looking AT the binocular. For
instance, you can see when one binocular is FMC and another is not, but no one
could ever tell by looking at a binocular if the lenses were produced by a fast
machine polish or slow precision polish which is purported to produce a much
finer quality lens. No one can tell by looking at a multicoated lens if extreme
care was taken to measure the thickness of the coatings to 1/4 wavelength needed
for precision premium coatings. And no one can tell by looking at a binocular
if the prisms selected for this quality level have passed critical inspection
or if they are the prisms that got rejected by critical inspection for some
other brand. These are just some of the
major production differences which cannot be seen, but would make a huge
difference in performance. These are the
types of qualities that can only be seen by observing with and comparing the
We know United Optics and Kunming Optical, both in Kunming China, have had this
Oberwerk Ultra style binocular available for a quite a few months, and while no
one has come right out and stated positively where they are getting their
shipments from, it is possible, and in my opinion likely, that all or at least
some of the US and European distributors are getting these manufactured in the
A review of the United Optics website Series 8 binocular models shows what I
believe is this binocular and describes the features that are being described
by some or all of these distributors.
Also, a review of the Kunming Optical Instruments Company Limited shows these
may or may not be a branch of the same company, but they show the same
Binocularschina was started in 1998... In Feb., 2001, we formed a second
corporation Ufind Optics Co., Ltd. which handles all exports... And, for the
last three years, we've been able to control or partly own 11 factories which
specialize in different stages of binoculars production...These factories are
all based in Kunming...we changed our company name to Kunming Optical
Instruments Co., Ltd in Dec., 2003...Beginning from Feb. 1st, 2004, we'll do
business in the name of "Kunming Optical Instruments Co., Ltd."
With a binocular of this level of quality, it seems from advertising that none
of the current importers are skimping on anything. They all seem to advertise
the same degree of high quality lens polish, premium coatings and rugged build
quality. It would appear from initial published in-depth reports that is
exactly what we are getting. QC from the
vendor may be the only variable.
The Oberwerk Ultra 15x70
The Oberwerk Ultra 15x70 Stats and
Performance Measures Incidentals
Objective lens caps are the pop in kind, rather than the slip over old style. The
binocular comes in a nice latched and lockable case with form fitted foam. The foam is all covered with a soft felt
lining. Included is a padded neck strap
and a good rigid L bracket for mounting the binocular on a tripod.
Size - Weight Well, the Ultra is a heavy 15x70.
Weight measures at 5# 5oz. For
comparisons, the Fujinon FMT-SX 16x70 weighs 4# 12oz and the Oberwerk LER 15x70
weighs 3# 2oz. Overall length is 10.625
inches or 270mm, almost identical in size to the Fujinon 16x70.
Strengths-Weaknesses I think what may be the most significant strength of these
binoculars is mechanically the apparent ruggedness and optically the apparent fine
contrast. A weakness, at least from my
point of view, is the need for a little more eye relief for eye glass wearers.
Mechanical Operation The eyepiece diopter is stiff.
It starts out with a little pop when you attempt to readjust it for
focus. After that it moves smooth. The main barrel hinge is fairly stiff. It is not going to move once you set it for
your IPD. Basically, with the stiff
hinge and stiff diopter, once you set this binocular for your own use, you
won’t need to adjust it again. Nothing moves unless you intend to move it. Fold down rubber eye guards are medium soft and
very wide. They are comfortable, but do
not block all outside light from the eyes.
Close Focus One noticeable difference in actual vs specified values became
apparent quickly. The specified close focus of this binocular is 10 meters.
That's 33 feet. With eyeglasses correct vision, I measured close focus of 120
feet or 36 meters!
AFOV – TFOV Full field of view spans from Gamma Delphinus, (Y)Del to Eta
(n)Del, almost exact. This
is 4.35°. This is very close to the specified 4.4°, and it is wider than the
4.0° Fujinon and about the same as the Oberwerk 2003 15x70. It gives an Afov of 65°.
Exit Pupil At close focus exit pupil measures approx 4.9mm = magnification
Focused on stars exit pupil measures approx 4.68mm = magnification 14.95x
This is perfectly normal and is about expected.
Diopter Adjustment / Focus
Speed With my eyeglasses corrected vision, the eyepieces are both between
+1 and +1.5 diopter for focus at infinity. For close focus they are both at +6
dipoters, with no room left to turn when focused at a distance of 125 feet. Eye lens focus rotates thru 325°. Eye lens focus travel is 6mm.
Therefore, the eye piece is turned through 54°
of turn per 1 mm of in-focus. I would consider that slow focus, a valuable
feature to have incorporated into the design.
Exit Pupil Distance / Usable Eye Relief The eye lens is deeply recessed. With eye guard folded down for
eyeglass wearers, I measure 8mm recess to lens and 11mm from eyecup to exit
pupil point. With eye guard extended for
non-eyeglass users I measure 13mm from outside of eye guard to lens and 6mm
from eyecup to exit pupil point. So total
exit pupil distance is about 19mm, but maximum usable eye relief is only 11-12mm.
Having the eye lens deeply recessed is good in that it keeps the lens
away from both eyeglasses and eyelashes.
However, I wish the eye relief were a little longer for us eyeglass
wearers. When looking with both eyes, as
we intend with all binoculars, I cannot see the outer right edge with my R eye
and I cannot see the outer left edge with my L eye, but together with both eyes
I can see to both edges. The L eye can see the far right edge of field and the
R eye can see the far left edge of field. It seems as though I can see the
entire fov, but the field stop is somewhat blurred. When I took my glasses off
to have a quick look, I noticed the field stops more distinct. These are
similar to how I use and see with the Fujinons. So, I’d estimate that I’m loosing less than 5%
of the outer edges of the field of view.
Without my eyeglasses, the entire view was seen easily.
Inter-pupilary range is adjustable from
a minimum 56mm to maximum 75mm. However,
the minimum IPD with supplied tripod adapter installed is only 58mm.
Tripod and Adapter The screw slot for the tripod adapter is recessed about 3-4mm in
from the body of the prism housing. That means that you cannot use a typical
wide flat binocular adapter with these binoculars, it would rub on the housing,
marring the rubber coating, or it may not even screw in. In this photo, the IPD is set at 62mm. The thickness of the L adapter is only
A very nice sturdy, Pentax shaped, narrow metal adapter is
provided with the binocular. It holds the binocular very stable and secure. However, even it is not narrow enough to allow
this binocular to reach the minimum IPD setting. It prevents the binocular from closing to
less than 58mm, eliminating the last 2mm of usable close IPD from use. If you have very close set eyes, as some do,
you may need to search for the narrowest tripod adapter you can find, similar
to the Pentax shaped adapters.
You could handhold this binocular for brief periods, but this
binocular really needs a mount. I used
this binocular on a variety of mounts including a Bogen 3130 head on a Bogen 3211
tripod, Bogen 501 head on a Bogen 3246 tripod and a Universal Astronomics
Unimount Light on a surveyor tripod. At
only 5.5# this binocular did not overload any of these mounts.
Cutoff Both prisms completely span the entire prism shelf. There are no
edges of prisms exposed. However, the backside of the front prism protrudes
slightly into the light path. I could see it in both barrels. This causes one
form of what we refer to as prism light cutoff. Even upon close inspection, it
was barely perceptible in the exit pupil. Without measurements, I would
estimate the cutoff at 1-2%. This is blocking light only from the outer few mm
of the objective lens. I considered this minor light blockage inconsequential.
Reflections - Baffles The insides of the barrels are fine ribbed matte black/gray. No internal reflections were seen at any time
while viewing any objects other than the moon.
With the moon just outside the fov, the half moon caused undesirable
reflections off the inside of the barrel.
This should probably be expected.
Focal Length Overall length is 10.625 inches or 270mm. Based on my method of
calculation for determining focal length, I estimated focal length of the
objective lens at 302 to 313mm. Call it
F = 310mm. The aperture is an
unencumbered 70mm. Therefore this
binocular is found to have a focal ratio approx. f/4.4. Eyepieces have a focal length between of 20mm
and 21mm. Eye lens = 24.5mm in diameter.
Collimation Collimation was nearly dead on. Checking numerous times on a 1
arcminute double, I could barely see any degree of minor mis-collimation. Checking to a 1 arcmin double star at 15x, I
would easily be able to see even if collimation was off by 20-30 arcseconds.
These aren't even off by 15 arcseconds. Images merged completely. The field of view in the barrels overlaps
In my Oberwerk BT100, at 62x, I can see it is merged to within
just about 20-30 arcseconds separation.
At 44x, images merge easily for me.
At 25x I can’t see any separation in the images at all. Few people would be able to see 15-20
arcseconds miscollimation in a 15x binocular.
Allowable tolerances are wider than many experienced observers can
actually put up with. A reasonable (more
stringent) tolerance for error would be 15 arcminutes apparent error in
vertical step, the worst error. An “apparent
error” of 15 arcminutes would be seen if a single star appeared double with
true misalignment of 1 arcminute, but viewed magnified by a 15x binocular. Convergence and Divergence, both horizontal
errors, allow slightly greater error.
This is not your typical binocular where the end user can simply
push aside the rubber and turn conditional alignment screws with a jeweler’s
screw-driver. Professional investigation
reveals there are three collimation screws and that accessing the inside 3rd screw
is NOT a job for the layman. This binocular has a tilt-plate arrangement
with prisms mounted to a spring-loaded prism shelf. The shelf or plate is adjusted via these three
screws. Two of the screws are accessible from the outside of the prism
housing. To access the third screw, you
must open up the binocular. Not recommended!
In fact this would release the nitrogen and the binocular would no
longer be waterproof.
The best advice I could give; If this binocular arrives out of
collimation, send it back for adjustment.
Resolution Point Source
On-axis observation, I could clearly see Gamma Delphinus as elongated and could
tell the primary from the secondary, but would stop just short of calling it
split. That's 144 arcseconds apparent elongated. From these actual readings it
falls right about where I would expect.
The Ultras could clearly see the four components of the Trapezium,
but I must admit the two closest could easily have been still touching. Because one is slightly brighter, it was easy
to see those as two and not just one. With the closest components at 8.7",
that is about the best on-axis resolution I've seen. I would call it suspected at 130 arcseconds
USAF Resolution Tests
15x70 Oberwerk Ultra actual and apparent readings
actual = easily see 6.82", seen clear 6.08", horz seen, vert suspect
apparent = easily see 102", seen clear 91", horz seen, vert suspect
For comparison, here are some values from other binoculars:
16x70 Fujinon FMT SX clearly see 6.08", suspect 5.4", no see
15x70 Oberwerk 2003 clearly see 6.82", horz only 6.08", suspect
12x50 Nikon SE clearly see 8.61", see both 7.65", no see 6.82"
16x70 Fujinon FMT SX clearly see 97", suspect 86", no see 77"
15x70 Oberwerk 2003 clearly see 102", horz only 91", suspect 81"
12x50 Nikon SE clearly see 103", see both 92", no see 82"
Just for kicks, with a 2.5x multiplier attached behind the eyepiece of the
Ultra, for a modified power of 15x2.5=37.5x, I could see resolution clearly to
3 arcseconds (mono view), and it was seen but just barely to 2.7
arcseconds. I could not see 2.4
arcseconds. For comparison, using the
Fujinon 16x70 with multiplier (=40x), to equalize I moved several feet further
away from the target and could see the same 2.7 arcseconds resolution, but still
no better than that. Essentially, I
would say the Ultra has the same limit of resolution as the Fujinon.
Off Axis Resolution Using
From previous testing on numerous binoculars I have found the correlation of
photopic USAF resolution : scoptic point source resolution is between 90:155
arcsec and 95:160 arcsec, or approx 1:1.7.
From data previously reported above:
15x70 Oberwerk Ultra actual and apparent USAF readings
clearly see 6.82", horz clear, vert suspect 6.08", see orientation
clearly see 102", horz clear, vert suspect 91", see orientation only
USAF off-axis resolution measured
at 50% out from center, see 8.61", for an apparent res of 129 arcsec
at 75-80% out from center, see 13.65", for an apparent res of 204 arcsec
Using the correlation noted above, I can predict apparent point source
resolution at 50% out = 219 arcsec res and 347 arcsec at 75-80% out.
Compare this to some actual off-axis point source resolution measured;
100 Herc 14.2" seen clear out to 55% = 213 arcsec at 55% out
Stf 485 Cam 18" seen clear out to 60% = 270 arcsec at 60% out
Theta Ser 22" seen clear out to 65% = 330 arcsec at 65-70% out
The estimated point source resolution based on USAF are not to far off from some
of the actual readings that I have.
So, I compare those estimated results to off-axis field sharpness of other
binoculars on my charts. 219 arcsec res at 50% out and 347 arcsec at 75-80% out
is only met or exceeded by a handful of binoculars; the Obie BT100 (entirely
dependant on choice of eyepieces), the Fujinon 16x70, the Pentax 16x60, Nikon
SE 12x50, Obie Mariner 10x60 and the WO 7x50 ED. Those are the top of the class
on my charts. This seems to place the Oberwerk Ultra in the top group for off-axis
Field Sharpness This is basically a term used to define how sharp or how poor the
image gets in the outer field of view, without any attempt to define which
aberrations are the cause of the distortions.
The use of the word distortion here is not meant as displaced star
image, but distorted size or shape of the point image; bloating, elongated,
curved, by various aberrations, mostly due to curvature, spherical aberration,
astigmatism and coma. This term
distortion is what helps define the measure of field sharpness.
Distortion The Ultra 15x70, GO20x70 and Obie v2003 15x70 were all compared to
see the distortion of the image of a star in the outer edge of the field. Using a double star of known separation in
the same field of view, or at least near the field of view, so I could pan back
to it as a reference scale, I measured the size of the distortion. In this case
I used the stars in the head of Draco, choosing a star that would end up near
the edge of field of view while at the same time I could also see Nu Draco
which is a 62 arcsec double. The spread on the distorted star images was almost
exactly the same as the spread in Nu Draco.
At approximately 80% out in the field, a bright star was elongated to
about a half arcminute in length. At
near 90-95% out, the star was elongated to one arcminute in length. There was not a significant difference among
the three binoculars.
For comparison, a new pair of Meade 5000 26mm plossls in the BT100
shows approximately the same amount of 60 arcseconds distortion in the image
near the edge. The Fujinon 16x70 has
about 40 arcseconds distortion at the very edges. A pair of 26mm TV plossls in the BT100 shows
about 15 arcseconds of distortion at the extreme edge of field. A pair of 14mm TV Radians in the BT100 shows
less than 6 arcseconds distortion at the extreme edges.
Five out of my 7 top binoculars (BT100 excluded) with the sharpest pinpoint
images in the outer field of view have 52, 51, 51, 50, and 45° AFOV. The only
binoculars with a wider field of view that make it into the top seven are the
Fujinon 16x70 and the Nikon SE 12x50.
Generally, the wider the Afov of the eyepieces, the more quickly aberrations
show up in the outer portions of the fov.
This Oberwerk Ultra 15x70 has an Afov of 65°. So, unless it is in a class with the Fujinon
FMT-SX 16x70 (65° Afov) or the Nikon SE (60° Afov), it might not be expected to
achieve the rank of having some of the sharpest pinpoint images in the outer
edges of the field.
Sharpness in the outer edges of the field of view is reduced by a
combination of aberrations from the objective lens and the eyepieces. In the Ultra, stars begin to show minor but
acceptable elongation parallel to field edge at 55% to 60% out from center. It
begins to get unacceptable about 70-80% out. Significant elongation really
distorts stars at 80-85% out.
The 15x70 Ultra can see theta Ser, a 22” double star, at 65-70%
out from center. This means at 70% out
it has a sharpness rating of 330. The Ultra can still see 16 Cyg at 80% out,
therefore the Ultra, at 80% out, has a sharpness rating of 585.
By 70% out the Ultra is still keeping up with the sharpness of the
Fujinon. By 80% out the Fujinon pulls away. Between 65-70% out the GO 20x80 has
an average sharpness of about 500-600, not as good as the Ultra. By 75-80% out the GO 20x80 drops to 750.
Compared to the Ultra 15x70, in all cases the Fujinon 16x70 was
able to resolve the pairs 15% to 20% out further towards the edge of field. The
Fujinon could resolve both 15 Aql (38") and 16 Cyg (39") right at the
very edge of the field stop, 100% out.
The Fujinon could resolve theta Serpens (22") at 80-85% out from
center. The Ultra could only see theta Ser to 70% out from center. In most
cases the Garrett Gemini 20x70, using the average of uneven readings, sharp
field closely matches the Ultra out to about 65%. Beyond that it drops off. What I see is this Ultra binocular seems to have a fov sharpness
that is not pin-point sharp all across the field, or as some people might say,
sharp edge-to-edge. Stars begin to show
minor acceptable distortion at 55% to 60% out from center. A 22" double at 65-70% out is a pretty
stringent test. At 75% out I could not see a 22 arcsec double as a double star.
By 85-90% out that same 22" double is distorted to a size of approx 1
arcmin and cannot be recognized as stars. I would put the usable field at about
75-85%, not as good as the best, but better than many.
Aberrations True Distortion True Distortion is related to image scale across the FOV. If you look at a square centered in the FOV,
with pincushion distortion, the sides of the square will be bowed inwards. With
barrel distortion, the sides will bow out. It is almost impossible to see these in the
night sky. However they show up when
observing straight lined terrestrial objects.
This binocular displays no
detectable pincushion or barrel distortion.
(In the paragraph above I have addressed true distortion. In all other instances here, the use of the
word distortion is not meant to describe displaced image as defined by true
distortion. It is used generally to
describe distorted size or shape of the point image; bloating, elongation or curving
of the point image by various aberrations, mostly due to curvature, spherical
aberration astigmatism and coma.)
With the Trapezium placed at the center of the fov, Stf 747, a 36” double at
the base of Orion’s sword, is placed at about 50% out in the fov. At 50% out, these are showing some aberration
of the point image, but not real bad. The double is still easily seen. Refocusing on this 36” double star at 50% out
in the fov (without moving the image in the field of view, so in this case
focusing on the image at the 50% out position), shows that nearly all of the aberration
in the point image can be removed. However, when you do that, the image in the
center is thrown out of focus, so the Trapezium now looks like one blob. This
is a telltale sign that indicates field curvature. Curvature is the only
aberration that can be focused out. In some instruments it is suppressed by a
field flattener lens. In the Ultra we
see that curvature is present and it enlarges or distorts the point image at a
location about 50-60% out from center to a size of about 15-20 arcseconds.
I rarely ever refocus my binoculars. Once I'm focused for precise images at the
center of field, I leave it alone. Curvature is an aberration that can be focused
out, but not many users would focus it out.
Many would just move the binocular if they could to center the object of
interest and allow whatever is going on in the outer field to just take place. It becomes a problem when, just as many
binocular observers do, you are using the entire field of view to observe an
object and re-centering is not an option.
Stars refocused at 50% out required turning minus 1 dipoter tic. Stars further out required more. I did not find this an acceptable
Beyond 50% out, a few other things start to come into play. Please keep in mind,
the variety of aberrations causing image distortions in the Ultra is not really
bad at all. I'm just trying to identify which aberrations are present.
In the outer edges of the field of the Ultra, coma begins to present itself.
Stars begin to appear with a brighter point towards the center with a small
flared fan shape towards the outer edge. If you could see a ray trace from a
single star of all the rays of light formed by the objective, you would see
most of the points all hit the same spot. That's the bright point towards the
center. But then, some of the rays formed from the outer edges of the objective
lens begin to miss the bright spot and get spread out in a fan shape. This
results in the classic comet shape. This is fairly typical in binoculars.
Seldom do we find a binocular that does not have some coma present. In the Ultra coma is present in the outer
edges of the fov, but fairly well controlled. It cannot be focused out.
In the outer field of the Ultra, we begin to see astigmatism. Astigmatism
begins to spread the star point image out in an elongated shape. Refocusing the
Ultra on a bright star in the outer edge of the field shows the elongated image
You can tell it is astigmatism by racking focus in and out past
the point of best focus. If the orientation of the "line" flips 90°,
it's astigmatism. There is a clear indication that astigmatism is present. It was not overwhelming and was not terribly distracting
since it was noticed at 80% out. This
is not uncommon in binoculars. Astigmatism
cannot be focused out.
Spherical Aberration It would be very difficult to tell, but with the presentation of
the three aberrations noted above, I thought I did not see any spherical
aberration. Well, maybe just a little. When I focused out the curvature at 60%
out, the point image at 60% out was not
as fine as the on-axis precisely focused point image, so this may indicate a
little SA is present. If present, spherical aberration is not easily noticed
and soon becomes totally overwhelmed by the other aberrations.
I could see some minor CA on Vega, some blue with Vega on-axis. A hint of false
blue color was seen on Altair. Sirius
shows a blue spike. No color was seen on Deneb. So while I saw some minor on-axis CA, No off-axis color was seen on any
bright stars. All these very bright stars showed the distinct spiking often
seen on bright stars. No other objects viewed throughout the remainder of several
night showed any of these affects.
As far as true color, Mu Cephei,
Betelguese and Aldebaran all showed up as a distinct orange color. Albireo shows its yellow and blue.
If minimum CA correction is assumed at 1/2000 F, then 1/2000 F = 1/2000
x 310 = 0.155mm. If 1mm of focus travel
= 54° turn, then 0.155mm = 8.5° of turn.
About one third of a dipoter mark represents the in/out focus of the
full extent of the CA correction. It may be possible, since there is a slow enough
focus turn, to focus out logitudinal CA.
The near full Moon was so bright I could not look at it without
hurting my eyes. I went in and got my sun glasses and that helped a lot.
Careful eye position was required to view the moon on-axis without CA. It was
easy, even though the moon was kept centered in the fov, to tilt my view and
see a thin band of yellow along the fully lit edge of the Moon. The on-axis view could be easily positioned
to completely eliminate CA.
Lateral Color Error Each
color (wavelength) focuses at a different focal length. That means also that each color results in a very slightly different
magnification. Since image scale varies with wavelength,
objects off-axis show color fringes because variance in magnification causes
color images off-axis to not coincide.
In essence, lateral color is a form of distortion. This is why much more color is seen
off-axis than on-axis.
Lateral Color showed up when a partial Moon was moved
to a position off axis. With the fully
lit edge of the Moon towards the outside edge, the Moon would show a thin green
band. With the fully lit edge of the Moon towards the inner fov, then the inner
edge (the fully lit edge) of the Moon would show a thin yellow band. Lateral
color on the moon is not unusual.
Summary of Aberrations So, what does this all mean?
Well I've already stated the outer field correction in the Ultra is
pretty good. I believe I noted earlier
that the combined aberrations show the extreme off-axis star image is bloated
to about 1 arcminute, not to bad at all.
Curvature adds 20 arcseconds of bloating to the star point already
by 60% out. If coma were not present the
star images due to astigmatism would look like long lines, generally running
parallel to the field stop, sort of like little sections of arcs of a circle.
When astigmatism is combined with coma, the comatic fan shape gets elongated to
the classic seagull, the wings grow longer.
While most all aberrations are
present, this is not a binocular that is suffering from serious aberrations. I'm
just taking the time to identify what aberrations are present and show about
how much they seem to be affecting the image.
We should be so lucky to have all binoculars present images like this.
Light Transmission Total light transmission will be determined primarily by the area
of the aperture and the quality of the coatings. Premium fully multi-coated binoculars can
transmit 95-96% of the total light gathered.
Also important for total transmission is illumination of the exit
pupil. That will be discussed later.
Coatings Compared I checked the coatings by comparing to several other models I own.
The coatings on the Oberwerk Ultra are:
Less reflective than the 2003 Oberwerk 15x70 and Pentax PCF 10x50 WP.
About equally reflective as Oberwerk Mariner 10x60, BT100 and WO 7x50 ED.
Equally or slightly more reflective than the Fujinon FMT-SX 16x70.
The coatings are definitely more reflective than the Nikon SE 12x50.
No binocular I own has matched the non-reflective character if the Nikon SE
coatings. This is my top-of-the-line. Held at the same angle you can look into
the Oberwerk Ultra or the Fujinon FMT-SX or the Oberwerk Mariner and you can
just see your face with variations in light and dark areas. Pick up a Nikon
Action Extreme or some moderate quality binocular and you can see detail such
as eyes or rims on glasses. Looking into the Nikon SE, you have a hard time
even seeing the outline of your head and you cannot see any features on your
face at all. The Oberwerk Ultra coatings
are definitely towards the high end in the broad scheme of things. Out of
the 35 or so binoculars that I've tested, among a few just less than the very
best, I've selected 4 of maybe the top 5-6 to compare with the Ultra and the
Ultra seem to fall right in the middle of that group.
Limiting magnitude is slightly different from Light Transmission in that LM is
also affected by magnification. Given two binoculars of equal aperture and
equal quality, that should have the same transmission, the one with higher
magnification will have deeper limiting magnitude. A 10% increase in magnification will result
in approximately 0.1 mag increase in limiting magnitude.
Over a period of several nights of observations under different
sky conditions, I used a variety of binoculars to record numerous readings of
faintest stars, or limiting magnitude.
These are the best results achieved condensed from those various sessions. I used my detail chart of Cr399, the
Coathanger for these readings. Naked Eye
Limiting magnitude (NELM) is recorded for each night to show varying
Some of the binoculars used for the Observing comparisons. From left to right. Garrett Optical 20x80
TWP, Anttler Optics Sky Sweeper 20x80, Fujinon FMT-SX 16x70, Oberwerk Ultra
15x70, Oberwerk LER 2003 15x70. I
carefully centered and cut 70mm holes in lens caps so I could use the Garrett
20x80 as a 20x70 in comparison tests. It has been referred to here as the GO
NELM mag 5.0, before and after readings. Moon rising.
Ultra 15x70 spotted mag 10.83 and 10.84,
but could not see 10.93.
Fujinon 16x70 saw the mag 10.84
Garrett 20x70 spotted mag 10.95. Persistence also netted mag 11.02.
NELM mag 5.4, Milky Way faintly visible. No Moon.
Sky conditions very transparent.
Oberwerk Ultra 15x70 saw 10.83, 10.84, 10.93, 10.95, 11.02 and 11.04.
Stars of mag 10.4 were seen steady and 10.6 seen most of the time. Mag 10.80 and 10.83 could be noticed pretty
quickly. Mag 11.05 could not be
seen. I would estimate mag 10.4 seen
100% of the time, mag 10.6 – 75%, mag 10.83 – 50%, 10.95 – 20 to 25%, and mag
11.02 seen only 10% of the time spent looking.
Garrett 20x70 saw deepest
mag 11.02 and 11.04, but not 11.05.
Oberwerk v2003 15x70 could only see deepest mag 10.7 and 10.83.
Nikon SE 12x50 saw mag 10.52 and only to a maximum faintest mag 10.6.
NELM Mag 5.4 NELM. two
bands of Milky Way faintly visible at zenith. Cr399 was naked eye. Two
different mag 5.4 stars were seen, but mag 5.6 could not be seen.
Oberwerk Ultra 15x70 faintest seen 10.95,
10.96, 11.00, 11.02, 11.08
Fujinon 16x70 faintest seen 10.95,
10.96, 11.00, 11.02
Anttler 20x80 faintest stars seen mag 10.95,
11.00, 11.02 and 11.05
Garrett Gemini 20x70 faintest stars seen mag 10.96, 11.00, 11.05 and 11.08
NELM mag 5.4 again. two bands of the
Milky Way faintly visible at zenith. Cr399 was naked eye. Mag 5.6 could not be
seen. Conditions identical to previous
Oberwerk Ultra 15x70 faintest seen 11.00,
Burgess LW 20x80 faintest stars seen mag 10.84, 10.95, 11.00, 11.02 and 11.05
Oberwerk v2003 15x70 faintest stars seen mag 10.6, 10.83, 10.84
Megrez 80 used this night for comparison to higher powers. Also, I
wanted to check some of the other stars I'd been looking for but couldn’t see.
Yes, they are there.
Megrez 80 SD II with 14mm Radian 36x80 faintest seen 11.63, 11.71, 11.74
Many readings are taken because sometimes stars are seen and sometimes not. At these limits of visual ability, it is
difficult enough to see, let alone see every limit sample every time. More readings give a consistent grouping
around the highest value reached for each binocular. There are far more readings, not all reported
here, both easier and attempts beyond the limits reached here.
The GO Gemini 20x70 in many tries could not see stars of mag 11.10
The GO Gemini at full 20x80 in previous tests, best skies, has seen to mag
The only two binoculars that saw 11.08 were the Oberwerk Ultra and the GO
Most observations were repeated to confirm the stars seen.
The Anttler 18.5x80 saw the 11.05 star only once.
The Ultra glimpsed the mag 11.08 star numerous times.
All stars fainter than mag 10.6 were seen only with averted vision
in binoculars, although some of them, mag 10.83, 10.84, could be seen most of
Mag 10.4 and 10.5 stars were all seen fairly constant.
Stars mag 10.95 and fainter were seen maybe only 10% of the time at best.
Mag 11.05 and 11.08 stars were seen maybe only 2-3 seconds at a
In the Megrez 80, I could see mag 11.02 direct, but mag 11.5 was
TV85 with 14mm Radian 43x85 mag 11.68 previously in mag 5.2 skies
Garrett Optical Gemini 20x80 mag 11.3 previously in mag 5.6 skies
Fujinon FMT-SX 10x70 mag 10.85 previously in mag 6.0 skies
Nikon SE 12x50 mag 10.8 previously in mag 5.8 skies
Attached here is the
chart showing all the stars that were used for testing Limiting Magnitude. Try observing some of these targets with your
instruments in your local conditions to find out what your equipment is capable
If all quality is equal, then a 20x80 should be able to see about
0.5mag deeper than a 15x70. A 20x70
should be able to see 0.35 mag deeper than a 15x70. Given the sizes, the Anttler, which operates
at 18.5x80 should have been able to see nearly the same or slightly deeper than
the Garrett masked 20x70. With equal quality, both of those should have been
able to see about 0.3 magnitudes deeper than the Fujinon or the Oberwerk
Ultra. What we see from the results is
the Fujinon 16x70 and the Oberwerk Ultra 15x70 held the positions right at or
near the deepest magnitudes seen. This
gives an indication of higher light transmission in these two binoculars.
As far as Light Transmission measured by
Limiting Magnitude, the Oberwerk Ultra holds right up to or exceeds the mark
reached by the Fujinon 16x70, the GO masked to 20x70mm and the other lesser
quality 80mm binocs. Premium
coatings and better contrast provide greater transmission that allows an
instrument to go a little deeper and reach or exceed the performance of lesser
quality instruments, even though those other instruments have higher
magnification or larger aperture, or both. The
Oberwerk Ultra exhibits crispness in contrast that seems to allow faint light
points to pop into view.
Exit Pupil Illumination This is one of those pieces of information that cannot be
determined by observing, but requires measured testing. It can make a big difference in the image we
see. Here is a profile of the exit pupil
outer portions of the exit pupil may not be fully illuminated, some central
portion of the exit pupil is fully illuminated by the full aperture. In this central
portion of the exit pupil, light gathering and resolution are based on the full
aperture. It is fair to say the outer
portion of the exit pupil is not receiving light from the entire objective,
therefore the effective aperture in the outer portion of the exit pupil is less
than the full aperture. Most every
binocular blocks some of the light from the outer portions of the exit pupil.
The illumination of the exit pupil is what Roland Christen talked
about in some of his comments about this new line of binoculars. How bright the
image appears and how well contrast is achieved is due in part to how well
illuminated the exit pupil is. This
15x70 has a very well illuminated exit pupil. I included a graphic attachment
here showing a comparison of the Ultra 15x70, Fujinon FMT-SX 16x70 and the
Oberwerk 2003 15x70. The Ultra lies in between them, but it is much closer to
The Fujinon 16x70 comes out on top for all light entering at any point on the
objective within the central 50% of the lens. Light entering the objective at
50% out from center illuminates the entire Fujinon exit pupil. In the Ultra, it
illuminates about 85% of the exit pupil. However, the Fujinon exit pupil
illumination drops slightly as the source light enters further out on the
Shortly after a point 70% out from center the Ultra overtakes the
Fujinon. Light entering at the very
edges of the objective leaves the central 20% of the Fujinon completely dark.
In the 2003 Obie 15x70, 40% of the center is left dark. Only the central 4% of
the 15x70 Ultra is dark. The Ultra is clearly the winner here.
For each instrument shown in the graphic attached, the top row of
circles shows the actual exit pupil image projected on a white board for each position
of the entering light beam, that position stated for each image,. Assuming that ep image can be rotated about a
central axis point, the large circle shows the percentage of the exit pupil
fully illuminated, partially illuminated, or not illuminated at all.
For comparison I include here note data on one of the best
performances I have measured, the BT100 with 14mm Radians. I also include the
Fujinon FMT-SX 10x70. I found the
comparison to the Ultra interesting.
Oberwerk Ultra 15x70
exit pupil is 100% illuminated by light at 45% out from center
exit pupil is 50% illuminated by light at 96% out from center
exit pupil is 48% illum (4% dark) by light from the very edge of the objective
Fujinon FMT-SX 16x70
exit pupil is 100% illuminated by light at 50% out from center
exit pupil is 50% illuminated by light at 90% out from center
exit pupil is 40% illum (20% dark) by light from the very edge of the objective
Oberwerk 2003 15x70
exit pupil is 100% illuminated by light at 40% out from center
exit pupil is 50% illuminated by light at 83% out from center
exit pupil is 30% illum (40% dark) by light from the very edge of the objective
Fujinon FMT-SX 10x70
exit pupil is 100% illuminated by light at 35% out from center
exit pupil is 50% illuminated by light at 85% out from center
exit pupil is 35% illum (30% dark) by light from the very edge of the objective
Oberwerk BT100 with 14mm Radians
exit pupil is 100% illuminated by light at 65% out from center
exit pupil is always more than 50% illuminated
exit pupil is 55% illum (0% dark) by light from the very edge of the objective
The Ultra is clearly providing illumination of the exit pupil that moves it up
a class. In addition to premium
coatings, simple transmission calculations and limiting magnitude tests, which
actually show the Ultra performs better than some equal sized and even some
larger sized binoculars, these illumination tests are one more factor that help
explain Why it performs better.
Oberwerk Ultra 15x70 Observing Sessions
side by side on
various nights with (among others) Fujinon 16x70, Garrett
Gemini 20x70 and Anttler Sky Sweeper 18.5x80.
Contrast Allows You to See More
Magnification improves the ability to resolve because objects are
seen at a larger image scale. However,
the qualities of contrast and resolution in an optical system are best observed
when you have side by side comparisons and the smaller optics are seeing equal
to or more than the larger optics. This
most definitely cannot be due to magnification.
I believe it can be attributed to contrast, the result of better
coatings, better illumination and better baffling.
I ordered a pair of 100mm lens caps that fit snuggly over the
front end of the Garrett Gemini 20x80. I carefully centered and cut 70mm holes
in each so I could use the Garrett 20x80 as a 20x70 in comparison tests. It has
been referred to here as the GO 20x70. I
also used the Anttler Sky Sweeper 20x80 (which really only has a magnification
of 18.5x80) as is. These notes were my
impressions of general observing.
I viewed many deep sky objects with the Ultras. Several that were
nice to see were M71, a prominent but small hazy patch; M57, still very small
but obviously not a star, no dark center; the North America nebula, not
distinct, but some areas noticed, an indicator of good contrast; the Double
Cluster, the Owl 457 and Stock 2 all pretty sights; NGC 7789, a few suspected
resolved, also an indicator of good contrast.
Views of M35, M37, M36, M38 were easy.
M31 was beautiful. M32 was easy and M110 was a faint glow. The arms of
M31 grew with averted vision and I would guess it's extent was about 2°. M78 and M1 were both fairly bright. I easily spotted stars of mag
10.5 to 10.7 in
M45 without much effort.
The near full Moon was so bright I could not look at it without hurting my
eyes. I went in and got my sun glasses and that helped a lot.
All three binoculars required careful eye position to view the moon on-axis
without CA. It was easy in all three, even though the moon was kept centered in
the fov, to tilt my view and see a thin band of yellow along the fully lit edge
of the Moon.
Lateral Color showed up when the Moon was moved to a position off axis. With the moon towards the right, then the
outside edge (the fully lit edge) of the Moon would show a thin green band.
When the Moon was moved to an off-axis position towards the left, then the
inner edge (the fully lit edge) of the Moon would show a thin yellow band. The
Fujinon added a slight purple when towards the left. Lateral color on the moon is not unusual.
None showed significantly greater CA than the other. All three were about
equally affected. None were so distracting that I wouldn't use them for moon
viewing. In fact, the on-axis views in all three could be easily positioned to
completely eliminate all CA. The on-axis detail in lunar features was sharp and
Extended Object Views
I viewed several OC, GC and nebula and noted differences in the views. Some of
the objects viewed are listed here:
oc M26 - in GO 20x70, see 1 or 2 stars resolved with faint fuzzy splotch to the
north. Both F16x70 and U15x70 see one resolved speck and the remaining fuzzy
area was barely seen.
oc 6664 - Both F16x70 and U15x70 detected some very faint averted specks at the
correct location. The GO20x70 instantly detected 2 or 3 faint specks. This
result is probably more in line with the LM test than with extended objects.
pn M27 - GO 20x70 sees a rectangular shape. Both F16x70 and U15x70 can see the
neb is not round, but the shape is less defined. I thought the U15x70 gave the
gc M71 - Both F16x70 and U15x70 see M71 as difficult, not bright, sometimes
needing averted vision to see at all. The GO20x70 saw more of the diffuse area,
and the object was always visible.
gc M13 and M15 - In the F16x70 and the U15x70, both gc showed as a much
brighter center with a fainter outer ring. In the GO20x70, M13 and M15 both
showed a larger extended area of the outer ring around the core.
en NGC7000 - All the binoculars could see portions of the North America nebula. The Fujinon
appeared to provide the best contrast between the fairly bright background and
the faint nebula.
oc NGC 7789 - in Cas has many very faint
stars and is often seen in binoculars as just a spot of glow. Very good dark
nights with clean air allow seeing more. Recently I observed this cluster with
my 150mm refractor using a 27mm Panoptic for 44x150. I counted 85 faint and very faint averted
vision stars. Last night using binoculars, although they were too dense to
count, I suspected seeing about 20 resolved stars with the Garrett 20x70. With
the Anttler 18.5x80, I could only
suspect seeing 10-15 stars. Both the Fujinon 16x70 and the Oberwerk Ultra 15x70
showed an estimated 10-15 stars clearly resolved. I suspected seeing about 8-10 resolved stars
with the Burgess 20x80 and the Obie v2003 15x70. The Burgess and Obie 2003 were
about equal on this cluster. The Oberwerk Ultra 15x70 showed a nicer image than
either the Burgess or the ‘03 Obie 15x70.
The continued quest
for IC 342 Several
nights recently the sky has been pretty transparent. Milky Way has been visible
a lot lately. And I've been mixing up my viewing sessions between late night
and early morning. This is the record of
some early morning attempts at finding an elusive object.
Tues. Sept 26, 06, 4-5 AM Oberwerk Ultra 15x70
I woke early and went out just to observe a different sky than usual. The
instant attraction to M42 captured my attention for a brief period. It is just so darned beautiful to look at!
The Ultras saw extension forming long wings curved out NW and SE with the
little ball of M43 at the head. The Trapezium was clearly visible as 4
components. I scanned around at leisure for a while. Taking note of how nice the sky was, I
decided to try again for IC 342 in Camelopardalis.
I didn't have any charts out with me, so I took a crack at this from memory. North
of Kemble's Cascade lies the extremely faint surface brightness face on galaxy
IC 342. I thought I saw it immediately. There was clearly a broad diffuse glow
located at the location. I suspected seeing it every time I looked at this
spot. Could this really be it? I’ve been questioning my observations of this
object for several years now.
Wed, Sept 27, 06, temp 48° Oberwerk
Conditions same as yesterday. I spent a minute or two looking around naked eye
and found 3-4 stars all mag 5.5. I didn't try very hard, so I suspect NELM was
a bit fainter than that.
I went right for IC 342. Once again, (and without charts, but I know this
location very well), I followed the path from Kemble's Cascade pointing north.
This time I landed on the spot of IC 342 and immediately saw it. There was no
question. The faint glow was quite
obvious. This morning for the first time I can definitively state that I was
able to see IC 342. That is a face-on galaxy that, IIRC, has a surface
brightness of about Sb mag15.0.
The glow of IC 342 (not really a glow, more like a thin gauze) was
sort of like the faintest background portions of the North America nebula, not
anything near as bright as the Gulf of Mexico portion. When you look at the North America nebula, there sometimes
appears to be a very faint extension of the diffuse nebula that extends out
north and west of the Gulf of Mexico, up into the region that
would be Canada. It's difficult to see where it ends. This is
similar in some respects to how IC 342 appears.
I think another good example of how faint IC342 appears might be similar
to M74, only larger, more spread out.
Although some might say these are not difficult objects, that may be
true for a mag 6.5 sky. This is a mag
There was no question that a large circular diffuse patch was present in the
view. It was not really brighter towards the center, but it was difficult to
see exactly where the diffuse edges ended. I would describe it as an evenly
bright diffuse patch about 20 arcminutes in diameter. It could be seen looking
right at it. It could be seen panning over it. It was seen averted. It was distinctly present in the view no
matter what method of viewing was used.
These observations show the position and appearance exactly located where I
thought I suspected the presence of an extremely faint diffuse spot several
times in previous observations. In the past I have made many attempts to see
IC342 with instruments such as Oberwerk 25x100 IF, Oberwerk LER 15x70, Garrett
Gemini 20x80 TWP and Fujinon FMT-SX 16x70.
I think now that some of those times I suspected the presence of
something, I may have actually seen it. Today there was no reason to question
or suspect if it was seen. It was plainly visible. I spent an hour scanning the skies looking at
clusters and patches of dense star clouds in the Cas-Per Milky Way. I returned
to IC 342 at least a dozen times and saw it each time I returned.
Although favorable conditions must be present to see such an object, without a
doubt it also requires the use of premium instruments. Only a binocular with excellent contrast
could have shown this object. There are
a few objects in my observing lifetime that I have seen only in
binoculars. All of them were found after
many attempts and then only with instruments of better quality. This Oberwerk Ultra is one that exhibits
excellent contrast and the ability to show some of the most difficult objects.
Overall Viewing Experience
The Ultra 15x70 always seemed to be showing me just as much as the Fujinon
16x70. There are some notes of objects above that actually show contrary to
that supposition, but it didn't seem that way in general viewing. It took a bit
of persistence to see those differences. For instance, on one night the Fujinon
recorded a slightly deeper LM and certainly the Fujinon has better off-axis
sharpness of view. But the natural viewing experience is more often of brighter
objects centered in the field, so these limits may not always come into play.
In all cases the larger image scale of the GO 20x70 made a lot of things easier
to see. For instance M57 was much easier to see in the GO 20x70 than either of
the other binoculars. There was never something that could be seen in the
smaller binoculars that couldn't be seen easier in the GO 20x70. However, I'm
not sure that would hold true for some very faint or broad extended objects
such as vast areas of nebula. Most
objects viewed were not at the limits of performance. I
never tried for IC342 with the GO20x70.
There were several times that I thought the image appeared brighter in the
Ultra 15x70. I doubt that the slight difference in the size of the exit pupil
would have made brightness noticeable, although it's possible. At the very
least, I think this gives a good indication of the contrast and transmission in
the Ultra 15x70. I think the contrast in
the Ultra was one of the most notable characteristics.
I like individual focus binoculars for astronomy. A binocular such as this one does not change
settings from one session to the next.
Just put it on the mount and it is ready to go. There is no fiddling around with this
binocular, no tweaking the collimation, no refocusing. Take it out of its case, mount it, and
view. It’s that easy.
Is It Worth It? As far as cost, let’s look at some of those I’ve compared it to in
Oberwerk Ultra 15x70
new $349 Fujinon FMT-SX 16x70, about $600 new, about $450 used
Garrett Optical Gemini 20x80 TWP new $269
Oberwerk LER 2003 model 15x70 new $149
As for quality, consider this: Although it may not come out on top
as the best, it is being measured here to some pretty tough standards and it
doesn't seem to have any serious stumbling blocks. Essentially, I would say the
Ultra has the same limit of resolution as the Fujinon. While most all aberrations are present to
some degree, this is not a binocular that is suffering from serious aberrations. The Oberwerk Ultra’s coatings are definitely
towards the high end in the broad scheme of things. This 15x70 has a very well illuminated exit
pupil, rivaling the Fujinon. The Ultra’s
Light Transmission holds right up to or exceeds the mark reached by the Fujinon
16x70 or the GO masked to 20x70mm. In
short, this Oberwerk Ultra is a very good binocular. I usually like to refrain from doing so, at
least until I've had many weeks and opportunity to try out something new, but in
two months from what I've seen and recorded so far, I'd recommend this Oberwerk
Ultra 15x70 to anyone.