Extra large fov binocular

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michael feist
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Extra large fov binocular

Post by michael feist »

WIN_20220510_14_55_39_Scan (3).jpg
WIN_20220510_14_55_39_Scan (3).jpg (46.59 KiB) Viewed 646 times
I acquired this second-hand binocular yesterday. Seems good. Interested to see if the fov is as much as 10°! Regards mike f.
David Frydman
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Re: Extra large fov binocular

Post by David Frydman »

Hi Mike,

A nice binocular purchase.

Large eyepieces, maybe Bertele or Erfle.

Greenkat binoculars tend to have a lot of distortion and overestimate their fields.
I would think 9 degrees is more likely, but for a 7x50 that is good.

Greenkat binoculars also tend to have short eye relief.

There may be JE and JB numbers on the body or even inside the front, which give the Japanese maker, if indeed Japanese.

Coatings seem good, but are the prisms coated?

Also hopefully well aligned and clean inside.

How heavy is the binocular?

Enjoy the view.

I have a Greenkat binocular, which has Leica markings. It is claimed to be a Leica binocular but is completely fake.

Regards,
David
brian livesey
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Re: Extra large fov binocular

Post by brian livesey »

Are the eyepieces in this binocular likely to be Kelners or even Achromatic Ramsdens? Mike is bound to know that when buying secondhand binoculars, we should look through the big ends to check for dust, fungus and damaged prisms.
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David Frydman
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Re: Extra large fov binocular

Post by David Frydman »

Some Greenkat binoculars have three element eyepieces with excessive distortion to achieve wide fields, but the eyepieces on this 7x50 seem too big for that.

However, counting reflections will give an idea of how many elements.

There are some white reflections, which suggest some surfaces are uncoated.

Regards,
David
brian livesey
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Re: Extra large fov binocular

Post by brian livesey »

In most, if not all, of the binoculars I have or had David the eyepieces have three elements: Copitar, Mirage, Telemax, etc. Possibly all made in the same Japanese factory. As for the Celestron Skymasters, I don’t know the eyepiece type.
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michael feist
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Re: Extra large fov binocular

Post by michael feist »

:roll: Yes, this binocular is clean within and seems well aligned. It is indeed heavy...I weighed them on the kitchen scales, result was 2lb 5⅞oz or 1074 g. The fov is certainly not quite 10° but could just about get γ (Phecda) and ε (Alioth) Ursae Majoris in the fov, so probably between perhaps 9°and 9½°(by measuring the star atlas). Stars were fine, the brilliant Gibbous Moon was fine in itself but there was a floating very pale ghost when panning across it. Perhaps because, as you suggested, the prisms are not coated? The hinge is rather too stiff but once set is ok. I bought it from Clock Tower Cameras in Brighton, one of the few sources locally now. As for whether truly Japanese, the disc on the mounting screw does say 'Made in Japan' although I could not locate a JE or JB letter. The body of the binocular have a serial number of 75- 66302. Certainly an interesting and useful purchase despite my difficult with bifocal vision, particularly as my dodgy left eye is now somewhat cataract dimmed. Thank you for you interest, everyone one. By the way, used it this morning, from the Park. Venus and Jupiter no longer sharing the fov. Jupiter and Mars not yet sharing but possibly about equally separated by the Venus and Jupiter distance. Regards mike f.
Last edited by michael feist on Thu May 12, 2022 4:49 pm, edited 1 time in total.
David Frydman
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Re: Extra large fov binocular

Post by David Frydman »

Mike, it is indeed a nice binocular.
Something I would have bought.

But Greenkat do overstate their claims.

I have a Greenkat 8x40, which is called the Ten, the claimed field.
From memory about 9.3 degrees actually.

There is a Soviet 8x30 with a genuine 13 degree field. Extremely rare.

Greenkat calls your binocular Navigator, which suggests Marine.
But not independent eye focus, so probably not waterproof.

It states magnesium body, but it is rather heavy.

The ultra violet coating is another sales blurb.

The stiff hinge is probably hardened grease.

The 75 may well mean 1975.

It is likely Japanese.

I also have a not too troublesome cataract in one eye.

Enjoy using it.

Regards,
David
michael feist
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Re: Extra large fov binocular

Post by michael feist »

Thank you again David for your detailed reply. Regards mike f.
brian livesey
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Re: Extra large fov binocular

Post by brian livesey »

My cataracts are mild despite having had them for many years. How much eye relief do you get Mike with this binocular?
The best quality binocular I’ve purchased was from a secondhand shop for £18. It was an immaculate German 7X50 naval glass ( identified by its serial number ) with independent focusing on both eyepieces. Star images were perfect to the very edge. It’s something else I wish I’d kept... .
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michael feist
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Re: Extra large fov binocular

Post by michael feist »

Eye relief is fairly small but the eye cups are adequate and comfortable when handheld. When mounted on a tripod perhaps slightly awkward especially if looking high in the sky. Ignoring the few instruments that I had as a lad ...ie brass naval telescope, 8" Newtonian, 6" homemade Newtonian, 10x50 (I think) binocular, a small homemade brass-tubed refractor, and angled ex-gov. elbow telescope, and a couple of other binoculars used for birdwatching, I still have a complete list of binoculars, monoculars, refractors, spotting scopes and small reflectors, bought and used to date. The Greenkat 7x50 in number 236. It is hard to say which was best or which I wish that I still had. That ex fov angled scope perhaps would perhaps be nice to still own. Of course it may not have been as good as I imagine. Regards mike f.
brian livesey
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Re: Extra large fov binocular

Post by brian livesey »

As for your homemade six-inch reflector, did you make the optics? I’ve cobbled together quite a few Newtonians over the years, but the optics were always bought out.
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michael feist
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Re: Extra large fov binocular

Post by michael feist »

WIN_20220513_06_41_43_Scan.jpg
WIN_20220513_06_41_43_Scan.jpg (37.88 KiB) Viewed 581 times
When we acquired the 8" less optics from Gadsden's garden we also took various grades of carborundum powders and jeweller's rouge and following a particular guide book, I attempted to make a 6" using two 'porthole' glasses. I got as far as finishing the grinding and then most of the polishing, although by that time this last step was not completed very well. However did send it away to be 'silvered' and finally mounted it on a open wooden beam and presumably bought a flat and eyepiece. It was a bit of a bodge-job really but I believe I did use it to view Comet Seki-Lines which could not be reached using the 8" which of course could not be moved around to avoid the bushes in the northwest.
The image posted has an interesting link with the story of my bodged-up scope. Not so long ago, an astronomical friend said that he had found an old book with my name in it. It was the book we used to make the mirror. The book was published in 1956 and really interesting was the fingerprint in jeweller's rouge on one of the pages...either mine or my father
WIN_20220513_06_41_43_Scan.jpg
WIN_20220513_06_41_43_Scan.jpg (37.88 KiB) Viewed 581 times
's. Regards mike f.
brian livesey
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Re: Extra large fov binocular

Post by brian livesey »

Thanks Mike. I remember those bottle green porthole blanks being used for parabolic mirrors. Being plate glass they were more prone to expansion and contraction than Pyrex,
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michael feist
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Re: Extra large fov binocular

Post by michael feist »

The only other Greenkat instrument that have bought, but since passed on was
WIN_20220513_07_27_19_Scan.jpg
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Regards mike f.
michael feist
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Re: Extra large fov binocular

Post by michael feist »

Interesting that you mention Copitar binoculars. The attached was bought and later passed on...
WIN_20220513_07_42_04_Scan.jpg
WIN_20220513_07_42_04_Scan.jpg (51.08 KiB) Viewed 574 times
Regards mike f.
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