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APM 20x80 ED and Oberwerk 20x65 ED

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#1 Cancri

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Posted 07 July 2021 - 07:50 PM

Hello,

 

I have seen comparisons of these two and there is something that confuses me a bit. Both seem to be listed as having equal FOV at the same magnification. I thought a larger lens would allow for a wider FOV?

The 80 mm lens catches more light, so you have a better picture (better visibility of faint stars), but I wonder how great the difference to the 65 mm is in this case? I wonder if it is worth investing into APM, considering the Oberwerk's are half the price (I can live with more weight).

I am unable to compare both side by side, so I would appreciate feedback from those who perhaps did.

 



#2 ECP M42

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Posted 07 July 2021 - 08:53 PM

A larger lens doesn't necessarily provide a larger field of view. Some field differences could result from the magnification. And basically it is the eyepiece that decides the width of the observation window (with the field diaphragm) and consequently, with the magnification, also that of the visible field.

 

Unfortunately the manufacturers / sellers do not provide the actual specifications, only the nominal ones. So (for example) you can never be sure that 20x actually equals 20 visual or angular magnification, and it could possibly be 19x or 21x (for example). So, even the field of view, you will have to actually measure it. 

 

Having never tried or measured them, I can't tell you the exact magnification and real field of view. But of course, these two models belong to two different levels of optical quality: you pay for what you get (... or something like that). So you will have two different results, regardless of the opening. And to decide between the two, you should really try them both, with your own eyes.

From what I can understand, I imagine that between the two there is a difference in optical quality of at least two steps: the Deluxe is 1 step below the Ultra (OB), which is one step below the MS ED (APM).

 

If I had to choose blindly, I would take the APM, but I think I could be satisfied with the Deluxe as well.

 

... make a good choice!


Edited by ECP M42, 07 July 2021 - 08:57 PM.


#3 Pinac

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Posted 08 July 2021 - 12:55 AM

Cancri,

 

see

https://binocular.ch...0x65-ed-deluxe/

in particular the section under „Image brightness“

Pinac


Edited by Pinac, 08 July 2021 - 01:02 AM.

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#4 Rich V.

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Posted 08 July 2021 - 10:13 AM

Thanks, Pinac, for posting a link to your fine comparison; just what Cancri needed.

 

And no, the size of the objective lens has no direct relationship to the FOV of a binocular, Cancri.  In fact, in most cases, a larger objective means a longer focal length, focal ratios remaining the same, raising potential magnification which would tend towards decreasing FOV, not making it larger.

 

The 20x65 is approx f6, though, while the 20x80 is much shorter at f3.8, which helps make the 20x65 have better color correction than the shorter focal ratio 20x80 bino.

 

Rich


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#5 Fiske

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Posted 08 July 2021 - 10:36 AM

The 20x65 is approx f6, though, while the 20x80 is much shorter at f3.8, which helps make the 20x65 have better color correction than the shorter focal ratio 20x80 bino.

This is true. However, in the case of the APM 20x80 ED, the color correction is likely to be superb. As good as that of the 20x65ED, which is also excellent. I don't own the APM 20x80 but do own APM 12x50 and 16x70 ED binoculars and they exhibit virtually no false color.

 

The main difference is that the x80mm image will be brighter without a doubt. Well, the other main difference is the price. wink.gif

 

Fiske


Edited by Fiske, 08 July 2021 - 10:36 AM.

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#6 Pinac

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Posted 08 July 2021 - 11:08 AM

……

However, in the case of the APM 20x80 ED, the color correction is likely to be superb. As good as that of the 20x65ED …

…..

 

 

As good as in the 20c65??

No, in my experience, that is not the case.

 

Pinac


Edited by Pinac, 08 July 2021 - 11:09 AM.


#7 Fiske

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Posted 08 July 2021 - 11:11 AM

You've done side by side comparisons of the APM 20x80 ED MS and the OB 20x65ED?

To be clear about this, I own a 20x65ED and am delighted with it. OTOH, I would be quite surprised to learn that an APM ED binocular exhibits false color.

Fiske


Edited by Fiske, 08 July 2021 - 11:17 AM.


#8 Rich V.

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Posted 08 July 2021 - 11:17 AM

As good as in the 20c65??

No, in my experience, that is not the case.

 

Pinac

 

In my experience comparing my similar formula f6 WO22x70ED against my 16x70 MS EDs, the WO, even at its higher mag, has better color correction day and night than the 16x70EDs.  Yes, there is some CA in the MS ED, although pretty minimal, and off axis. It certainly doesn't bother me.  Even the WO shows some CA if you look for it.   It's just that the 22x70 shows even less and is closer to "apo" than the APMs, FWIW.  The difference between f6 and f3.8 with similar glass formulations has its consequences.

 

Rich


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#9 Fiske

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Posted 08 July 2021 - 11:24 AM

Yeah. That makes sense. Thanks, Rich.

 

To minimal and off-axis I would add and non-consequential for astronomy use. They are different instruments with different fit and feel. Choosing one or the other based on specifications is somewhat problematic. From the perspective of optical performance, however, the big difference is not color correction but the brightness of the 20x80 compared with that of the 20x65 -- aperture also has its consequences. 

 

I do think the 20x65ED is one of the best values in binocular astronomy. smile.gif

 

Fiske


Edited by Fiske, 08 July 2021 - 11:24 AM.


#10 Rich V.

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Posted 08 July 2021 - 11:30 AM

You've done side by side comparisons of the APM 20x80 ED MS and the OB 20x65ED?

 

Fiske, you did read Pinac's linked review, right?  wink.gif



#11 Fiske

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Posted 08 July 2021 - 11:50 AM

Fiske, you did read Pinac's linked review, right?  wink.gif

lol.gif lol.gif lol.gif

 

Uh...

 

Looks like an excellent review. I will read it before any more comments. Thanks again, Rich.

 

Fiske

 

PS: Sorry(!) Pinac. wink.gif



#12 Fiske

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Posted 08 July 2021 - 12:02 PM

Actually, I have read the review before. That review is why I bought the 20x65ED in the first place. grin.gif

 

 

At night, when the eye pupils are dilated, the APM 20×80 shows a slightly brighter image of the nightsky than the Oberwerk.

To my eyes, the brightness difference between 20x65 and 20x80 binoculars is more than slight. The same thing goes for 10x42s and 10x50s, honestly. I find the brighter, more vivid, more colorful views compelling and engaging in side by side comparisons. It's not subtle to me. I haven't done daytime tests with the instruments, but would expect it to matter less if at all just as Pinac states. My preferred daytime binocular is an 8x42 -- not because it is brighter than a 10x42 (I own Monarch HGs in both magnifications) but because it is more relaxing and comfortable to hand hold.

 

High contrast daytime views are a more critical color correction test than astronomy, and I haven't done side by side comparisons of APM instruments and the 20x65ED in that scenario. The differences are less noticeable in astronomy use. Dare I say slight? wink.gif

 

Fiske


Edited by Fiske, 08 July 2021 - 12:11 PM.


#13 Rich V.

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Posted 08 July 2021 - 12:19 PM

 

To my eyes, the brightness difference between 20x65 and 20x80 binoculars is more than slight. The same thing goes for 10x42s and 10x50s, honestly. 

 

It should be noticeable; it's a 51% increase in overall brightness based on lens area.  The 42 vs 50 is 41%.  Again noticeable.

 

It makes me think of the photographic Zone System gray scale, though, where even a full f-stop step, 100% brighter, is just one shade lighter gray as in sky background.  

 

Rich

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#14 Fiske

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Posted 08 July 2021 - 12:57 PM

It should be noticeable; it's a 51% increase in overall brightness based on lens area.  The 42 vs 50 is 41%.  Again noticeable.

 

It makes me think of the photographic Zone System gray scale, though, where even a full f-stop step, 100% brighter, is just one shade lighter gray as in sky background.  

 

Rich

Thank you again, Rich. grin.gif



#15 sevenofnine

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Posted 08 July 2021 - 02:02 PM

Cancri mentions the 80mm's ability to see fainter stars. If the sole use is wide view astronomical is ED glass even necessary? Because of the small image size, 20x80's don't impress on lunar or planetary views anyway. Maybe the standard APM or Oberwerk 20x80 Deluxe would be the better choice? hmm.gif


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#16 ArsMachina

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Posted 08 July 2021 - 02:20 PM

It is all about contrast :-)



#17 Rich V.

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Posted 08 July 2021 - 02:39 PM

I really didn't notice a difference between the MS and MS ED 16x models regarding contrast, though.  They're nearly identical binos outside of the ED lens.  Very hard to tell them apart on the sky, IMO.  At only 20x, you're still not at a high enough mag to see a difference in fringing on stars outside of the very brightest.  Extended objects wouldn't be an issue for most anybody, I'd think.  High magnifications or daytime use are a different story for sure, but if we're talking about 20x for astronomy, no big deal.

 

If money is no object, though, the ED is more of an all-around use choice.  The APM MS achro will likely have a bit flatter field than the Obie Dlx achro but at a price.

 

Rich


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#18 Fiske

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Posted 08 July 2021 - 02:39 PM

I own the OB 20x65ED Deluxe, 20x80 Deluxe III, and the 25x100 Deluxe. smirk.gif And like them all. I don't think you can go wrong with any of them.

 

BUT, if I were picking only one of the three for astronomy, particularly from suburban skies, it's the 25x100 (IF version) hands down. Easy choice. Sure, the FOV is smaller, but it goes way deeper than the other two instruments. 

 

Fiske


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#19 Fiske

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Posted 08 July 2021 - 02:45 PM

I really didn't notice a difference between the MS and MS ED 16x models regarding contrast, though.  They're nearly identical binos outside of the ED lens.  Very hard to tell them apart on the sky, IMO.  At only 20x, you're still not at a high enough mag to see a difference in fringing on stars outside of the very brightest.  Extended objects wouldn't be an issue for most anybody, I'd think.  High magnifications or daytime use are a different story for sure, but if we're talking about 20x for astronomy, no big deal.

 

If money is no object, though, the ED is more of an all-around use choice.  The APM MS achro will likely have a bit flatter field than the Obie Dlx achro but at a price.

 

Rich

+1 waytogo.gif

 

I have been impressed by the flatness of the field in the OB 20x80 Deluxe III and the 25x100 Deluxe binoculars. The edge performance of either instrument is excellent. The 20x80 is remarkably sharp near the edge of the FOV -- comparable to the APM 16x70 ED at least. The edge performance of the 20x65ED is also excellent, as already noted.

 

Fiske


Edited by Fiske, 09 July 2021 - 02:33 AM.


#20 cbullock

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Posted 08 July 2021 - 07:46 PM

If the OB 20x80 Deluxe III is that good, why would one consider the 20x65 OB Deluxe?



Chris
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#21 sevenofnine

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Posted 08 July 2021 - 10:39 PM

Chris...the Oberwerk 20x65  and the APM 20x80 have ED glass. That makes a difference mostly in day time viewing and bright objects at night. At higher powers there's color fringing in high contrast situations. ED glass eliminates the fringing. Worth the price to get rid of it to some. Others aren't bothered by it enough to pony up the $$$$ moneyeyes.gif


Edited by sevenofnine, 08 July 2021 - 10:48 PM.


#22 Fiske

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Posted 09 July 2021 - 02:47 AM

If the OB 20x80 Deluxe III is that good, why would one consider the 20x65 OB Deluxe?

Chris

The color correction of the 20x80 Deluxe III is not as good as that of the 20x65ED. It's not just the matter of ED glass. As Rich pointed out earlier, the longer f-ratio of the 20x65ED also improves the color correction and overall sharpness. But that also gives the binoular a certain feel -- it's longer and bulkier than other binoculars in it's magnification and aperture range. It has a certain feel and character that some users love, so it has a loyal following. Preferences like that differ from person to person. You figure out your own preferences over time as you observe with different instruments.

 

Fiske


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#23 cbullock

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Posted 09 July 2021 - 04:14 AM

I really appreciate the wealth of knowledge and experience which you all bring to the table.

What would you consider to be "bright" objects ( other than the moon ) during night time viewing in which ED glass would make an obvious difference?
I use a pair of Nikon 12x50 SE and still see light spikes and halos on objects such as Vega. Does ED glass eliminate that?

Chris

#24 Fiske

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Posted 09 July 2021 - 07:56 AM

I really appreciate the wealth of knowledge and experience which you all bring to the table.

What would you consider to be "bright" objects ( other than the moon ) during night time viewing in which ED glass would make an obvious difference?
I use a pair of Nikon 12x50 SE and still see light spikes and halos on objects such as Vega. Does ED glass eliminate that?

Chris

Hi, Chris. If you are seeing halos around bright stars like Vega it could indicate a problem with your binocular, I'm sorry to say. I owned a Nikon 12x50 SE purchased new in the early 2000s. Last year I noticed halos around bright stars, the moon, etc. The binocular was sent to Suddarth Optical for cleaning. But the problem turned out to be defective adhesive in the eyepiece lens assemblies. You can read about my experience with the problem starting at this post.

 

It can't be repaired, unfortunately. Nikon no longer has replacement parts. Since I was the original owner, Nikon provided a replacement voucher coupon for use on their USA website to purchase new binoculars or whatever else I wanted from their site. They no longer make SE binoculars.

 

If you look through the objective end of the binocular -- the 50mm lens end -- with the eyepieces pointed at a bright light, the view should be completely clear with no hazing. If it looks hazed, the adhesive defect could be the problem. It helps to have another binocular to compare it with so you can see how clear it really should be. It should be absolutely crystal clear.

 

Fiske

 

PS: Image of defective Nikon SE lens doublets sent to me by Cory Suddarth are included in a later post on that topic.


Edited by Fiske, 09 July 2021 - 08:00 AM.


#25 jprideaux

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Posted 09 July 2021 - 07:58 AM

I really appreciate the wealth of knowledge and experience which you all bring to the table.

What would you consider to be "bright" objects ( other than the moon ) during night time viewing in which ED glass would make an obvious difference?
I use a pair of Nikon 12x50 SE and still see light spikes and halos on objects such as Vega. Does ED glass eliminate that?

Chris


Yes ED glass will help reduce light spikes and halos on bright objects. With refractors, there are three ways to improve the problems that not all light is focused at exactly the same place.

1. Use higher price specialty glass (ED). There are also different grades of ED glass.
2. Use a triplet (or 4 element petzval) design either with higher cost
3. Use a longer focal ratio (makes it physically longer)

For binoculars one typically wants low cost, manageable size, and good optics. You can’t get all three at the same time.

The OB 20x65 ED uses longer ratio (f-6) combined with an ED glass element to give better optics at the price of being longer than other binoculars in its aperture size.

The OB 20x80 III uses s triplet design but with inexpensive glass to keep cost down and the typical f-ratio of binoculars (perhaps f3.8 or something).

The Nikon 12x50 SE is reported to have an f-ratio of 3.7 and I’m not sure about the glass quality. I would think that if it had ED, it would have been advertised as such.

The APM 20x80 ED obviously uses ED glass (FK61) as well as the use of magnesium in the construction to keep weight down and is also waterproof to some degree. It’s f-ratio is most likely similar to other typical binoculars ( in range of 3.7 to 4).

Besides the moon, other popular bright nighttime objects are the planets, double stars, and other stars with distinct colors. There are also some DSOs that have near-by bright stars. At 20x I can see that Saturn has a ring (and not just elongated) with my OB 20x65ED (although the image is very small).
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