Binoculars: any cumulative effect of twin objective lenses?

[JulianFR]

This may be a dumb question, but does having two objective lenses in binoculars in anyway give a virtual increase in overall light gathering aperture, or do you just get two lots of (in my case) 70mm?

I don't know if that makes sense... I guess I'm asking with say my 15 x 70s is there a cumulative effect of giving, for example, a single objective of 100mm (just pulling a figure out of the air)?

Just curiosity on my part!

[Laurie61]

There is an improvement as your brain integrates the info from both eyes. I see about 0.5, or so, improvement in magnitude using both eye's, contrast is also a little better.   

[Tonys]

That's a really good question that I've often wondered about myself and it seems to make sense that the brain integrating the images ie what we see as overlaid images would increase apparent light grasp a little, as Laurie61 says.

[Richardisgreat]

the Brain needs to use both eyes to interpret a 3d image, using one eye by definition only allows one perspective of distance  and shape thus gives a 2d image.  I know this is not what Julianfr asked but just thought I would throw it in.  I know a chap in our Astronomy club that uses a bino viewer in his scope, I believe the  overall quality of the  image is increased simply because the brain can make out more shape and detail not because more light is collected, obviously the aperture of the scope is not changed so by rights the light collected must be split between two eyepieces, this given I would expect the light to be shared and actually each eye would receive less light than one on its own, I could very well be wrong about this, maybe  a physicist can help   

[Alfian]

Hi Julian, if you do a search fpr "binocular summation" you will find a lot of info showing the advantages of two eyes over one and not just in terms of equivalent light gathering (which is usually given as about 140%. Doing the maths converting the area to a single objective, your 70mm bins (assuming they might be full 70s which most are not) would give about 83mm. Steve Tonkins book Binocular Astronomy has a useful section on the "binocular advantage" and Ed Zarenski has contributed a lot of in depth study material on the subject on the CN forum.

[JulianFR]

Very interesting... Thanks all. Maybe it wasn't such a dumb question after all ;-)

I have already decided that when I win the National Lottery I'm going to buy a ginormous pair of optically hot astronomical binoculars.