Resolving Power

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mike a feist
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Resolving Power

Post by mike a feist »

Resolving Power of Binoculars. I came across this information in "Binocular Highlights" by Gary Seronik (S&T) and have not read elsewhere. Obviously the resolving power of low-power instruments does not follow the Dawes Limit which depends on the use of high-power, far beyond that achieved using binoculars. This author suggests that a better guide to resolving Power of binoculars is governed by the magnification, and by dividing the magnification into the number 300. Therefore a 10x50 binocular will have a resolving limit of 30". A 15x70 binocular will have a limit of 20". This seems reasonable in practice. Any comments? regards maf.
David Frydman
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Re: Resolving Power

Post by David Frydman »

Mike,
It depends what resolving power you use.
Unaided eyes resolution varies from as little as 0.5 arcseconds for a wire against the sky to several arcminutes for double stars.

Binocular resolving power primarily depends on how good your eyes are and to the quality of the binocular.

I could split Miizar unequal double at 14.4 arcseconds with 10x30 IS or 12x45 Russian, but not any more as my eyes have worsened within the last ten years.
Protected unaided eye sunspots can be seen at less than 40 arcsecond by many or 20 arcseconds by exceptional sight. Divide by 10 for a tripod mounted 10x binocular.
Resolution critically depends on brightness and contrast.
Venus transits are easily seen at 60 arcseconds with unaided eyes.

300 divided by magnification is too big for 20/20 or 20/15 vision if the binocular is tripod mounted.
However, 300 makes sense for equal brightness double stars using a hand held shaking binocular.

Just talking about resolution or resolving power is meaningless without defining what resolution you are talking about, and brightness and contrast.

Regards,
David
mike a feist
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Re: Resolving Power

Post by mike a feist »

Hello David,
Thank you for your clarifying thoughts. Of course everything depends on lots of other variables.
The author was actually taking about separating nu Draconis with binoculars.....this is of course is not difficult !
regards mike
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