Thread: Vintage Binoculars

The field of view would give the purpose away. Opera glasses have a very small field of view to zoom in on a single performer on stage. Opera glasses would be useless in the field. Even birding glasses have a wider field.

With such a small field it would be very difficult to even find what you are looking for in the field.

I never cease to be amazed at the breadth and depth of the knowledge pool here at SRP...

And to be reminded of what it feels like to hold the solid heft of a well made pair of binoculars as you scan the (insert your favorite memory here)....

Originally Posted by thebigspendur

The field of view would give the purpose away. Opera glasses have a very small field of view to zoom in on a single performer on stage. Opera glasses would be useless in the field. Even birding glasses have a wider field.

With such a small field it would be very difficult to even find what you are looking for in the field.

https://www.bing.com/search?q=binocu...&setlang=en-US

https://www.bing.com/search?q=wwi+bi...&setlang=en-US

Could go either way opera or field.

Bob

Way way back they used "spyglasses" monoculars which had good mag and tiny fields of view but before or around WWl they were being replaced with Binos already.

A slightly off-topic question about astronomical viewing with binoculars. I once read that ideally, the square of the power of the binoculars should be under the stated diameter of the lens elements to allow for brightness in addition to definition, the classic example in this case being 7x50 binoculars. Someone mentioned 5x30 binoculars, which would also work in this regard. Are there any other examples that folks know about and could share here?

Of course they sell binos for astronomical viewing. Check Meade and celestron and you'll see these huge monsters usually mounted in a frame and you sit in a chair while viewing. Most discoveries involving comets and asteroids are made by amateurs using these binos.

For astronomical viewing you need all the light gathering power you can muster so you want the largest elements possible so that means 50mm or larger-much larger on one end and large lenses in the eyepiece for eye relief.

With telescopes you obtain the mag by dividing the eyepiece diameter into the focal length of the instrument. The problem is smaller the eyepiece the darker the image and when you get down to below 5mm the pupil of your eye is larger than the eyepiece and it becomes harder to see anything so you need an ever bigger instrument.

Thanks, but what I would like to know is if there are other binocular formats that exist following the 7x50 and 5x30 examples, whereby the square of power is less than diameter in mm of the lens. 8x70?, 9x90?, etc. 7x50 seems to be the default as mentioned in astronomical guidebooks, and I imagine that as the power-diameter ratio increases, the binoculars become more unwieldy.

Originally Posted by Brontosaurus

Thanks, but what I would like to know is if there are other binocular formats that exist following the 7x50 and 5x30 examples, whereby the square of power is less than diameter in mm of the lens. 8x70?, 9x90?, etc. 7x50 seems to be the default as mentioned in astronomical guidebooks, and I imagine that as the power-diameter ratio increases, the binoculars become more unwieldy.

Absolutely no experience star gazing with binoculars but your question got me looking for info. From the little I have read you would be looking for a pair of binoculars with a 5mm exit pupil if you are older with larger exit pupils benefitting the younger crowd. The draw back to exit pupils larger than 5mm is that the objective lenses become very large adding greatly to the weight of the binoculars.

The higher the magnification the larger and heavier the binoculars become even if you go with a 5mm exit pupil. Higher magnification coupled with extra weight make it harder to hold the binoculars steady enough free hand. You will need a sturdy tripod with a counter weighted arm for easy hands free steady viewing of the stars. A Celestron SkyMaster 25x100 binocular weighs 156 oz/4.4 kilo and will not be hand hold able. Binoculars in 8X40 are not too bad to hand hold if braced but by the time you hit 10X50 you are talking serious weight and bulk.

Bob

Originally Posted by BobH

Absolutely no experience star gazing with binoculars but your question got me looking for info. From the little I have read you would be looking for a pair of binoculars with a 5mm exit pupil if you are older with larger exit pupils benefitting the younger crowd. The draw back to exit pupils larger than 5mm is that the objective lenses become very large adding greatly to the weight of the binoculars.

The higher the magnification the larger and heavier the binoculars become even if you go with a 5mm exit pupil. Higher magnification coupled with extra weight make it harder to hold the binoculars steady enough free hand. You will need a sturdy tripod with a counter weighted arm for easy hands free steady viewing of the stars. A Celestron SkyMaster 25x100 binocular weighs 156 oz/4.4 kilo and will not be hand hold able. Binoculars in 8X40 are not too bad to hand hold if braced but by the time you hit 10X50 you are talking serious weight and bulk.

Bob

Thanks for your comments. I have seen higher-power star-gazing binoculars for sale, 25x100 from your example, but this exceeds the power squared to diameter ratio I am talking about. 25x would equal > 625mm in this relationship. More realistically, it would have to be no more than 10x equaling > 100mm. 5x30 and 7x50 do this. I also would be using the binoculars with a tripod as it is far more stable that way. I'm just wondering if such examples do exist.

Originally Posted by Brontosaurus

Thanks for your comments. I have seen higher-power star-gazing binoculars for sale, 25x100 from your example, but this exceeds the power squared to diameter ratio I am talking about. 25x would equal > 625mm in this relationship. More realistically, it would have to be no more than 10x equaling > 100mm. 5x30 and 7x50 do this. I also would be using the binoculars with a tripod as it is far more stable that way. I'm just wondering if such examples do exist.

I do not know where this square root formula came from but the light going to your eyes from the ocular lenses comes through an opening, exit pupil, measured in mm. The larger the opening the more light gets to your eyes all else being equal but they are not. Poorly made binoculars with sub standard optical coating will not transmit the same amount of light as a properly made binocular with superior optical coating regardless of both having the same exit pupil. Add to that your eyes may not, if you are older, dilate wider than 5mm to make use of the extra light supplied by having an exit pupil larger than 5mm.

7X50 binoculars have an exit pupil of 5mm arrived at by dividing the size of the objective lens by the magnification. The 25X100 binocular has an exit pupil of 4mm which is less light that the 7X50. A 10X100 binocular would have an exit pupil of 10mm which not even a young person's eyes could dilate wide enough to use all the light being delivered. That is also twice the amount of light an older person's eyes could accommodate.

Bob