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Comparison of Oberwerk & Galileo 15x70s

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#1 Bill Grass

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Posted 30 April 2004 - 09:20 AM

Last night the sky cleared up just enough for me to compare my Oberwerk 15x70s to my new used set of Galileo 15x70s (bought from Tom T. :grin:).

Both binoculars look very simiilar. The Oberwerks are black while the Galileos are dark gray. Both have almost identical soft carrying cases. They're both obviously from the same factory in China.

The Oberwerks have BAK-4 prisms while the Galileos have BK-4.

The coatings of the Oberwerks are better than the Galileo coatings. Just by looking at the eyepieces & objectives, the Oberwerks have a deep green color (broadband fully multicoated) while the Galileos are much more blue ("fully multicoated," as it is stamped on the binocs). This was noticeable while looking at and near the moon. As I got closer to the moon, its glare was much more apparent in the Galileos than the Oberwerks. At one point I could even see the mooon reflecting from some part of the optics before I even zeroed in on the moon.

Other than that, the views are pretty much identical. Both binoculars show nice, clear views of stars. The softness around the edges of the FOV were both very similar (which was not very much at all). And the levels of chromatic aberration were both very similar (again, not very much).

I'd say that for somebody looking for a great value in 15x70 binoculars, the Galileos do a very fine job.

#2 EdZ

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Posted 30 April 2004 - 09:42 AM

Both binoculars look very simiilar. The Oberwerks are black while the Galileos are dark gray. Both have almost identical soft carrying cases. They're both obviously from the same factory in China.


I'll repeat this again. It's been said here at least a half dozen times before. These binoculars DO NOT come from the same factory.

Oberwerk 15x70 binoculars do not come from the same factory as any other U.S. 15x70 binocular. Oberwerk is a sole distrubtor.

edz

#3 BarrySimon615

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Posted 30 April 2004 - 09:53 AM

A word about prism types -

In porro prism binoculars (as are the two 15x70's described in this thread) there are two common prims types. They are correctly designated BAK-4 or BK-7. Perhaps BK-4 was a typo on the Galileo spec sheet? BAK-4 is made from bariusm crown glass and has a higher density. This works better in eliminating internal light scattering and in conjunction with other features usually found in higher grade binoculars that use BAK-4 prisms, produces images which are sharper. BK-7 prisms are made with boro-silicate glass which has a lower density, is less expensive and can primarily be recognized by noticing that the arcs of the exit pupil are cut off (4 arcs shadowed with a brighter square like exit pupil in the center). Accordingly there is some light loss with BK-7. However in view of all the revelations recently about vignetting and binoculars, this may be, to a certain extent, a moot point.

In any event better binoculars usually advertise BAK-4 as an advantage. From the practical point of view, it may not matter much. BAK-4 is harder to work and tends to be more fragile.

In respect to coatings, the color of coatings may vary depending upon the thickness applied, a deeper green often means a thicker coating and too thick is not good. While green may often be indicative of multi-coatings, it cannot be inferred that because the coating is green, the binoculars are fully multi-coated, they may in fact only have several multi-coated surfaces. Most will specify fully multi-coated as that is considered a plus, if they are fully multi-coated. "Broadband" is not an industry recognized term; it essentially means that the binoculars pass light along a fairly broad spectrum of visible light. (Ruby coated binoculars have a much narrower spectral band pass.)

Barry Simon

#4 Bill Grass

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Posted 30 April 2004 - 10:31 AM

I'll repeat this again. It's been said here at least a half dozen times before. These binoculars DO NOT come from the same factory.

Oberwerk 15x70 binoculars do not come from the same factory as any other U.S. 15x70 binocular. Oberwerk is a sole distrubtor.

Sorry, Ed. My mistake.


They are correctly designated BAK-4 or BK-7. Perhaps BK-4 was a typo on the Galileo spec sheet?

I dunno, Barry. BK-4 is what's stamped on the bincos themselves. Is there such a prism? :question:

#5 EdZ

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Posted 30 April 2004 - 10:49 AM

In respect to coatings, the color of coatings may vary depending upon the thickness applied, a deeper green often means a thicker coating and too thick is not good. While green may often be indicative of multi-coatings, it cannot be inferred that because the coating is green, the binoculars are fully multi-coated, they may in fact only have several multi-coated surfaces. Most will specify fully multi-coated as that is considered a plus, if they are fully multi-coated.


Barry is correct. Color of coatings is not a clear indicator of quality. However the Broadband multicoating applied to Oberwerk's 15x70 binoculars does tend to appear green. In some of their finer examples of binoculars the broadband coating will have a tendency to appear multicolored green/purple, depending on the angle viewed.

A much more telling test for comparing coatings is this. Allow daylight to illuminate your face. Look into the binocular objectives for reflections of your face. If you can see your face clearly and make out any detail in your face, the coatings allow too much light to be reflected back off the lens. If you can barely make out the outline of your face and cannot see any detail in your reflection, the coatings are preventing most of the light from being reflected back at you. This is what you want.

Also, allow light to shine into the binocular. Look thru the objective into the inner surfaces of the binocular. If you can see white reflections from any surfaces inside the binocular, either they are simply single coated or not coated at all.

Blue coatings are pretty much indicative of single coated MgF.

The term multi-coated could simply mean that one surface of one lens in the binocular is multi-coated.

Even the term FMC as advertised by Chinese manufacturers was found by Oberwerk to mean less than every surface is FMC. Once they discovered that they changed their specification. That was pointed out in the difference between the Oberwerk 2002 and 2003 models. The Chinese appear to offer FMC and premium FMC. Oberwerk now orders the premium FMC.

All of this is discussed in the "Best Of" threads in the posts related to coatings.

edz

#6 Bill Grass

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Posted 30 April 2004 - 11:44 AM

Thanks, Ed. I'll try that test when I get home.

#7 Dennis

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Posted 30 April 2004 - 12:21 PM

Thanks for your post Bill. I had wondered about the differences after seeing the Galileo's at NEAF. Having recently purchased my 15x70 Obers, Ed and Barry's discussions were very informative. I'll be trying the tests too.

#8 Guest_**DONOTDELETE**_*

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Posted 30 April 2004 - 01:29 PM

Barry or EdZ, can you inform us how the coatings are typically applied and how that affects the quality control? The coatings are supposed to be 1/4 wavelength in thickness. That's quite thin indeed! How does one be assured that you have applied a uniform coating of that thickness? Are the lens dipped & spun? Aersol deposition?

#9 EdZ

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Posted 30 April 2004 - 01:41 PM

I can only direct you to a source that describes the process.

Edmund Optics Technical Support

Vapor deposit seems to be the method I have seen described.

This link is posted in the "Links to Offsite Astronomy Sources" sticky post

This may help you understand some of the differences in the Chinese binoculars.
Description of levels of coatings in Chinese branded binoculars

edz

#10 Guest_**DONOTDELETE**_*

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Posted 30 April 2004 - 01:57 PM

Thanks EdZ!

#11 Bill Grass

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Posted 30 April 2004 - 05:35 PM

Okay, I checked out my reflection. The Galileo objectives showed my face pretty clearly. I could see detail in my face. I had to look for a few seconds to see my reflection in the Oberwerk objectives. I could see it, but it was a little difficult. Details were hard to see.

As far as the other test, should the light be shining through the objectives as I look through them, or should it be illuminating from the eyepiece end?

#12 EdZ

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Posted 01 May 2004 - 05:29 AM

Shine the light down thru the objective, so you can see if any reflections come back at you from the inside glass surfaces.

You have observed the apparent difference in the coatings on the outside of the objects. the amount of light you saw from your face that allowed you to see an easy reflection with detail is light that is not going through the objective to add light in the image you see when using the binocs. The more you see coming back at you is less that makes it thru the glass to form an image.

edz

#13 Bill Grass

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Posted 01 May 2004 - 10:47 AM

Thanks, Ed! I shined a light through the objectives and here's what I saw: through the Galileos, I saw white light reflecting back to me from an inside optical surface. In the Oberwerks, the left side reflected a green light, while the right side reflected both green and white. (The white may have been slightly purple.) And just for comparison, I did the same with my Ultima 10x50s & saw nothing but green reflected back.


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