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Kowa 7x35 10 degrees (Featherweight, Coated)

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#1 MT4

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Posted 17 June 2021 - 01:03 AM

How good are the optics in the 10-degree Kowa 7x35, one without Prominar in the name?  Could one use it ok with eyeglasses, e.g. by removing the plastic eyecups and putting on a couple of o-rings to maximize the eye relief?

 

Or would I be much better off with a modern 10-degree Kowa BDII 6.5x32 ?

 

P.S.  I've searched CN and found some old threads on wide-angle  Kowa 7x35 but they are all mostly about the Prominar version and have been archived.  That's why I've started this new thread.



#2 MT4

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Posted 17 June 2021 - 01:41 AM

Kowa 7x35 10deg.jpg



#3 SMark

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Posted 17 June 2021 - 01:47 AM

From my experience, the Prominar versions are generally equipped with Bk7 prisms, while the non-Prominar version are equipped with BaK4 prisms. I have compared them side-by-side and the BaK4 versions are brighter. Details here...

 

https://www.cloudyni.../#entry7390090 

 

And yes, O-rings and flat rubber washers will both work after removing the Kowa Eyecups. Details here...

 

https://www.cloudyni...s/#entry7580215 

 

The BDII 6.5x32 is also a very nice binocular, though for me it has not replaced the Kowa BaK4 Wide Angle 7x35 Porro.


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#4 MT4

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Posted 17 June 2021 - 01:59 AM

From my experience, the Prominar versions are generally equipped with Bk7 prisms, while the non-Prominar version are equipped with BaK4 prisms. I have compared them side-by-side and the BaK4 versions are brighter. Details here...

 

https://www.cloudyni.../#entry7390090 

 

And yes, O-rings and flat rubber washers will both work after removing the Kowa Eyecups. Details here...

 

https://www.cloudyni...s/#entry7580215

 

The BDII 6.5x32 is also a very nice binocular, though for me it has not replaced the Kowa BaK4 Wide Angle 7x35 Porro.

 

That's perfect.  Thank you very much SMark.

 

My interest in vintage, wide-angle binoculars all started with reading those vintage binoculars threads where you've been offering a lot of informative facts and opinions going back a decade or so.  When I created this thread to ask about the Kowa 7x35 non-Prominar, I was definitely hoping that you'd offer your usual facts and opinions on it smile.gif


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#5 pat in los angeles basin

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Posted 17 June 2021 - 09:13 AM

They both work fine for me. I use a bike innertube cut and contact cemented to the nearly flush surface (with lens) of the eyepiece. Works well. I seem to recall that someone used a thin layer of e-6000 as a soft barrier (it pulls off cleanly when you need to remove it- yet still durable) for a glasses wearer. That way, you can still screw on the eyecups Wonderful glass.. Regards, Pat


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#6 MT4

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Posted 17 June 2021 - 09:31 AM

That's very nice to hear.  Thank you Pat.

 

I've put in a bid for the Kowa 7x35 10-deg.   Fingers crossed that it'll be mine soon smile.gif


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#7 MT4

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Posted 19 June 2021 - 08:14 AM

The Kowa 7x35 10-deg non-Prominar is mine for the JPY equivalent of about 60 USD, inclusive of shipping.  I hope that's a reasonable price for it, and fingers crossed that it'll arrive in good shape smile.gif


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#8 MT4

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Posted 24 June 2021 - 09:02 PM

Just got my new Kowa 7x35 10-deg non-Prominar.  I haven't had much of a chance to evaluate it beyond taking a quick look at a nearby park but I can tell right away that it's a very nice addition to my growing collection.  What's not to like about a sharp 7x35 with 10 degrees of TFOV all of which I can see with my glasses on smile.gif  Also, I believe that it's BaK4 since the exit pupils are circular not diamond shaped.

 

If only the weather would be as nice.  it's been rainy and cloudy non-stop here for a week and a half now, with no end in sight ...



#9 SMark

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Posted 24 June 2021 - 09:13 PM

You have an outstanding extra wide angle binocular there, don't ever let it go. It's among the best in its class when considering sharpness and contrast. 


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#10 MT4

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Posted 24 June 2021 - 09:41 PM

Thanks a lot SMark.   

 

It was on your and Pat's recommendations that I decided to put in a bid.   I am very pleased with it and won't ever willingly part with it.   (I'm a firm believer in the philosophy that life is short and that when you find something/someone that you really like don't let go.)


Edited by MT4, 24 June 2021 - 09:46 PM.

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#11 MT4

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Posted 25 June 2021 - 08:27 AM

I've cleaned up my Kowa 7x35 and put a couple of O-rings on the eyepieces.   Eye relief is fine for my glasses and I can see the full 10-deg FOV.  Looking at a nearby city park at night, it's plenty sharp and clear.  Too bad the sky is full of white clouds and so there are no stars anywhere to be seen, naked eye or through my latest binocular addition.

 

 

 

Attached Thumbnails

  • Kowa_7_35_1.jpg
  • Kowa_7_35_2.jpg

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#12 SMark

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Posted 25 June 2021 - 12:45 PM

Wow, that's in really nice condition. Fantastic find!


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#13 MT4

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Posted 25 June 2021 - 05:04 PM

Thank you SMark.

 

By the way, the red O-ring idea is something I learned from you.  I saw a pix of your Nikon 18x70 with a red O-rings glued to the eyepieces and thought wow what a nice idea.  No prize for guessing the color of the O-rings I've put on my own Nikon 18x70.  So you see I have a quite few things to thank you for, SMark smile.gif


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#14 MT4

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Posted 25 June 2021 - 08:11 PM

I mainly use binoculars on the night sky but the weather hasn't been cooperating lately so I thought I'd do a mini daytime side-by-side comparison between my Kowa 7x35 10-deg and Nikon EII 8x30, looking at a nearby park and some buildings beyond it.  I am not experienced enough with binoculars to be able to discern technical details, so I am going to just describe what I saw through my eyes in layman's terms.

 

In the brightness department, the Kowa lost out to the Nikon, no doubt as a result of multi-coated vs. fully multi-coated and old coatings vs. modern coatings.  (My Nikon EII 8x30 was bought new late last year so should have the latest-and-greatest Nikon coatings.)

 

In the chromatic aberration category, which I think is more critical for daytime use than nighttime use, the Kowa pulled well ahead of the Nikon.  There's very little purple fringing in the Kowa whereas in the Nikon I could readily detect purple fringing away from the center of the view.  This alone makes the Kowa more comfortable than the Nikon for bright daylight viewing, though the Nikon's lighter weight is certainly an advantage when hiking.

 

In terms of central sharpness and edge sharpness, I am afraid I am not experienced enough to be able to properly compare the instruments for daytime use.  To my eyes, both felt plenty sharp and I didn't feel that the Kowa gave up much if anything to the Nikon.  I suppose that assessment of binocular central sharpness and edge sharpness is probably better done on the night sky where any defects are more easily noticed.

 

TFOV wise, the Kowa won though the Nikon's 8.8-deg TFOV is nothing to laugh at.  Prior to the acquisition of the Kowa, the little Nikon held the title of widest-angle, glasses-OK binocular in my collection.  (Note that the eye relief on the little Nikon is by no means generous, it's just that I've found a trick to make it workable with my glasses.  The trick is to use super-thin double-sided 3M tape to bring the rubber eyecups as close as possible to the top of the eyepieces.  I gain a hair more of eye relief this way but it's a hair more of critical eye relief that allows me to see the Nikon's full FOV with my glasses on.)

 

All in all, from a quick daytime comparison, the little Kowa did pretty well against the well-established, highly-regarded little Nikon.  This is especially sweet considering that I paid 60 USD for the little Kowa (used obviously) and some 500 USD for the little Nikon.  Now I have two little brother vs. big brother pairs that I really like:   Nikon EII 8x30 vs. Nikon 18x70, and Kowa 7x35 10-deg vs. Kowa Highlander Prominar.

 

Who knew that the world of binoculars and binocular astronomy could be so richly diverse and wonderfully rewarding smile.gif


Edited by MT4, 25 June 2021 - 08:16 PM.

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#15 MartinPond

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Posted 25 June 2021 - 10:31 PM

I have that same model,  as a   "Burton Space-King" ,

   with a Kowa marking on the 1/4-20 mounting thread..

   cleaned it up properly. 

 

I love the view.   It's an  11-degree / 578ft system, choked to 

  10 degrees, cleaner near the edges and excellent contrast,

   probably from cutting the light path through a full  1,2,1 80-degree

   eyepiece. A bit of 'dark glass' to reduce the scatter.   

     Contrast is a top factor for me.

 

There is no BAK7 'blue diamond' looking through mine.

Either there is BAK4, or more likely, the 7*10-degree cutoff

  has eliminated the difference entirely.

  I did clean things to maximize brightness, of course.


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#16 MT4

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Posted 26 June 2021 - 06:41 AM

When I cleaned up my Kowa 7x35 yesterday, all I really did was to wipe all exterior lens surfaces using Fujifilm lens cleaning liquid, the same liquid I use every now and then to clean my eyeglasses.  I see some small screws on the prism plate and wonder if it's safe to open up the prism plate to clean up something inside to maximize the brightness.

 

Since I have never opened up any binoculars and don't even know the first thing about collimating binoculars, I am a bit concerned that I might mess up the collimation.  I'd be quite upset if it did happen.

 

Would appreciate any tips for how to clean up the internals of the binoculars while minimizing the risk of messing up the collimation.  Thank you.


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#17 MT4

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Posted 26 June 2021 - 10:31 PM

Per Pat's advice, I just shined a high-powered LED flashlight on the eyepieces and looked through the objectives one of at a time.  The prism surfaces seem to be all clean.  So it appears that my Kowa 7x35 10-deg specimen is clean both inside and out.  I am going to enjoy it as-is, and I am never going to let it go.

 

I've been a member of this community for only 3 weeks and already I have received so much wonderful advice/encouragement from kind experts and learned so much in the process.  For me, this forum has easily the most impressive body of knowledge on binocular and binocular astronomy on the planet.  (I am not ready to declare it the most impressive in the whole universe just yet.  Who knows, there maybe more impressive brother/sister forums on exoplanets out there somewhere in the universe or multiverse smile.gif).  Thank you all !


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