I shined a laser into a 10mm eyepiece, and I only got an 8-inch spread at 2 feet.
Shining flashlights, I got anywhere from a few inches to 2 feet.
So...the divergence of flashlights varies enormously, and I know the
divergence of the laser beam actually varies in proportion of the laser beam width.
So....this not a standard quality of either source.
The laser through an eyepiece spreads and continues to spread.
It is divergent and uncollimated.
In optical engineering, light is only considered 'nicely collimated' when it
diverges at a tiny fraction of a degree, on an optical table.
In a slide projector, maybe a degrre or two. Spreading out a foot at 2 feet
would definitely be considered very un-collimated.
This is collimated light:
It is parallel...extremely parallel, not convergent or divergent.
I'm going by that definition.
I am also stating that a light cone inbound will experience different barriers than a light beam.
I'm just doing the science from my optics courses.
'nicely collimated' light from a cone coming from a flashlight or a laser and eyepiece makes no sense,
being an obvious violation of the very definition of 'collimated light'.
Is this lore vs. science?
The difference (in aparent aperture) doesn't matter much in telescopes, but
it can be serious in binoculars. It can make you believe that dozens of models
have been mysteriously short-sheeted in aperture even though all the size
and expense have been poured into a bigger lens. It sort of doesn't make any
Edited by MartinPond, 15 October 2014 - 10:12 PM.