Just for fun, Satellite watching

The image brightness of a sunlit scene can't be higher than the scene brightness. Google "conservation of radiance".

Cheers

Phil Hobbs

Smaller binox for the same image brightness.

Cheers

Phil Hobbs

...and your point is? Are you saying that binoculars don't intensify the image? Really?

Not buying it.

Yup, that's what I'm saying. If they could, you'd be able to make perpetual motion machines.

Cheers

Phil Hobbs

On Sat, 01 Nov 2014 22:21:53 -0400, Martin Riddle Gave us:

And neither make a difference when looking into the eyepiece of a telescope, as the image "dot" is small, and smaller than you small pupil.

Nothing like the 'image dot', complete with peripheral information, that enters one's eye in daylight.

It was an incorrect assumption made when the remark was made that it would be better.

The benefits of the mechanism of pupil dilation are for fully lit fields of vision... day or night.

Looking into the eyepiece of a telescope is NOT a "fully lit field of vision". It is typically a very dark zone fully surrounding a very small point of light, and when your eye looks at THAT small "point" it turns out to be image information. That small 'point' fits into the smallest human eye pupil.

The person needs to dilate his brain a bit.

So 10x50 binoculars, 10x80 binoculars, and the naked eye will view a scene with the same brightness? Tell me another one gramps!

Some Sky and Telescope articles on the subject.

If the pupil of the eye is 5 mm or less, that's right. Elementary optics, that. What do they teach these whippersnappers nowadays? ;)

Cheers

Phil Hobbs

What's right? Please explain WTF you're talking about.

What you said was right, though apparently you don't believe it: "10x50 binoculars, 10x80 binoculars, and the naked eye will view a scene with the same brightness."

Except that there's inevitably a bit of loss in the optical system of the binoculars, so they'll be slightly dimmer. As I said, this assumes that the pupil of the eye is 5 mm or less in diameter. More pupil area equals more light, other things being equal.

It's an interesting point, and you can show that it's true using the second law of thermodynamics. See e.g.

Cheers

Phil Hobbs

On Sun, 02 Nov 2014 16:04:29 -0500, snipped-for-privacy@attt.bizz Gave us:

No. He is saying that the image you see is not "intensified" merely brought down to a spot size for OUR use. One can still only gather what is there, and those little eye cups are what keeps peripheral illumination from playing a part in what gets put across your retina.

But you can still only see not what the optics are capable of focussing on and showing you a spot image of, but more precisely those focussed elements which are illuminated enough for some of those reflected photons to reach your retina. This is why as the lights dim, so too does your capacity to examine what the optics ALWAYS pick up perfectly. It is just simple ray tracing.

Essentially, he is saying that "intensify" is an incorrect term to use, but he didn't really explain it.

Neither did I as I branch a lot, and instruction has never really been a forte of mine. So 'rusty' isn't really appropriate either.