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Light gathering power of binocular Vs refractor?

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#1 Bob W6PU

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Posted 18 June 2006 - 02:17 PM

Is the effective combined aperture of your binocular additive?

To put it another way, do the two 50mm objectives in your 7X50 have the same light gathering power and resolution as single lens, 100mm refractor?

With microwave dish, receiving antennas, placing two of them side by side, increases the effective aperture and resolution, over that of a single dish.

The only difference between a optical lens, and a microwave( parabolic lens), dish antenna, is the frequency of the electro magnetic spectrum that they deal with!

Bob in NM

#2 Glassthrower

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Posted 18 June 2006 - 02:38 PM

Bob -

I don't recall the math involved, but the equation is not that simple. So the short answer to your question is no.

EdZ has authored several definitive threads on "binocular summation" - do a CN search for that phrase in quotes for the binocular forum.

Good luck and clear dark skies...

MikeG

#3 Pinewood

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Posted 18 June 2006 - 02:40 PM

Bob,

1. A 100 mm refractor has four times the light gathering power of a 50 mm refractor. Clearly if the effect were perfectly additive, which I doubt, the result of using two 50 mm. objectives would be that of a 71 mm. objective.
2. I think that the use of two parabolic dish antennae may require some sophisticated engineering and software to increase resolution. Also the distance between the dishes, as well as the size of the dishes determines the increased resolution. Baselines of thousands of kilometers are being used. Doing the same thing with optical telescopes is in its infancy as I do recall reading about this.
3. This subject has been discussed in this forum before and my recollection is that the increased limiting magnitude was marginal, but not insiginificant, but I cannot find the posts.
LATER: Here it is:
http://www.cloudynig...ll/fpart/1/vc/1

Clear skies,
Arthur

#4 Joad

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Posted 18 June 2006 - 03:34 PM

Good work, Arthur! :goodjob:

#5 Bob W6PU

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Posted 18 June 2006 - 04:32 PM

The reason that I was wondering is because I hadn't heard this mentioned before.

I will have to look up the threads that have been mentioned, and also see what I can learn from a Google search of the subject.

Actually, with just two lenses or dishes, the method is quite simple,and does not require any computer programs or complicated formulae.

In fact, I do this here, with some of my dishes.

Spacing two parabolic lens dishes, several wavelengths, and in phase, represents an increase over one, of Approx. 6dB or a power factor of 4X! As the spacing increases, the power gain increases!

If you could focus the Sunlight from two binocular lenses into ONE Single Point, onto a piece of paper, would it not be more intense(in burning power) than a single lens?

It will be interesting to research this, and learn why the two should differ since they both deal with focusing electro magnetic energy!

Cheers!
Bob in NM

#6 btschumy

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Posted 18 June 2006 - 04:57 PM

The reason that I was wondering is because I hadn't heard this mentioned before.

That's only because you haven't been on this forum that long. The subject seems to get beaten to death every few months.

Edz's Binocular Summation article has it all, but in a nutshell, the light from the two objectives is not simply summed. You may get the equivalent of 10%-20% increase in light gathering power and a 20%-40% increase in contrast. This is simply because the brain is more effective in processing light coming to both eyes.

For the same reason, you will get a small but significant increase in resolution when using two eyes. However, this is different from the why that long-baseline radio telescopes get increased resolution -- increased synthetic aperture.

With binoculars, the magnifications are generally too low to see the resolution limits caused by aperture-controlled diffraction effects.

#7 Bob W6PU

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Posted 18 June 2006 - 05:08 PM

Now that makes sense Bill, thank's for that Info!

Bob

#8 Pinewood

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Posted 18 June 2006 - 07:21 PM

This illustrates the nature of using a long array in radio detection:

http://antwrp.gsfc.n...d/ap060514.html

If I understand this correctly, each dish has the same sensitivity but synthetic aperture, the distance between the dishes provides the greater resolution. As Bill wrote, this is not the radio wave equivalent of binouclars.
However, there are some giant astronomical binoculars:
http://antwrp.gsfc.n...d/ap060514.html
which was the subject of a thread on this forum

Clear Skies,
Arthur

#9 EdZ

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Posted 19 June 2006 - 12:43 PM

Is the effective combined aperture of your binocular additive?

To put it another way, do the two 50mm objectives in your 7X50 have the same light gathering power and resolution as single lens, 100mm refractor?


No. Even if not using binoculars, two 50mm lenses do not have the light gathering power of a 100mm lens. LG is based on the area of the circle. As Aurthur pointed out a 100mm has four times the area of a 50.

But it's more involved when comparing the light from one lens to one eye vs the binocular summation of two lenses to two eyes. You would need an 85mm binocular to get the equivalent of LG delivered to one eye from a 100mm refractor.


1. A 100 mm refractor has four times the light gathering power of a 50 mm refractor. Clearly if the effect were perfectly additive, which I doubt, the result of using two 50 mm. objectives would be that of a 71 mm. objective.


This (second sentence) can be misleading if not understood properly, and is incorrect if referring to binocular summation. Aurthur has good reason to doubt. So if I may, let me reword this. If the effect were additive then the result of using two 50s would be that of a 71, ONLY IF the two 50s were delivering all of their combined light to ONE EYE. There are no common optical use instruments that do that. Also, that does not represent binocular summation.

Binocular summation, the effect of observing thru two 50s using two eyes, is measured as a 40% gain (by area) over that of one 50mm lens to one eye. Therefore, a 50mm binocular provides the light gathering equivalent of a single 59mm lens delivering light to one eye. The percentage binocular summation gain varies from 20% to 40% for light gathering, contrast, brightness and resolution. I have used the maximum gain here.

See the Best Of Link to Binocular Summation - Two Eyes vs One Eyed Viewing.

edz

#10 Bob W6PU

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Posted 19 June 2006 - 05:37 PM

Thank's for the feedback guys!

There's more to this than meets the eye( no pun intended) as it envolves the brighteness perception of one eye Vs two eyes!

From researching , comparing the energy gathering power of a pair of equal size lenses at the light spectrum, to another equal size pair of lenses , in the microwave

spectrum, theory shows that both will exhibit a power gain, over the single lens by itself!

Another example which came to my attention envolved this experiment.

Hold a simple magnifying lens of say, three inches in diameter,in one hand, and focus the Sun's image on a themocouple, and measure the maximum temperature produced.

Now take another three inch lens, and holding it in your other hand, spaced one foot apart, focus the Sun's image on the same thermocouple, so that you now have two focused solar images superimposed on each other.

The increase of light energy gathered by the addition of the second lenses will result in a higher measured temperature than with the one lens alone!

Very interesting, but it obviously doesn't apply to a comparison between a 50mm binocular, and a 100mm refractor .

As far as I'm concerned, the diameter squared law still holds...to wit... the 100mm lens will gather four times as much light as either 50mm binocular lens!

I'm missing something here, in the theory, and "coping out", but thats OK! :lol:

Bob in NM

#11 btschumy

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Posted 19 June 2006 - 09:29 PM

As far as I'm concerned, the diameter squared law still holds...to wit... the 100mm lens will gather four times as much light as either 50mm binocular lens!

I don't think anyone here is denying that.

#12 EdZ

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Posted 20 June 2006 - 05:05 AM

As far as I'm concerned, the diameter squared law still holds...to wit... the 100mm lens will gather four times as much light as either 50mm binocular lens!

I don't think anyone here is denying that.


Bob needs to recognize that two 50mm diameters does not equal a 100mm diameter.

edz


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