Re: Why does corona around the moon look less vivid when viewed thru binoculars

Hi, Gloria. I was puzzled by what you saw (for reasons outlined below), so
I actually submitted it to the METEOPTIC world-wide mailing list for
high-atmosphere meteorological phenomena (i.e., halos, sundogs, etc.)

In general, increasing the magnification of an extended light source (like
a lunar halo or corona) "spreads out" the available light over a wider
area. Normally, this has the effect of reducing the contrast of the light
source, especially against a bright background (like the moonlit sky!) Now
what I thought was interesting was that in some cases - such as observing a
faint nebula through a telescope - this contrast effect may actually work
the OTHER way: increasing magnification of both the background sky and the
nebula can actually INCREASE the contrast of the nebula...

But sure enough, the seasoned observers of the 'METEOPTIC' list confirmed
what you saw: increasing the magnification on these bright-sky phenomena,
e.g., from unity (your eyes) to 7x (your binoculars) actually tends to make
them get lost against the sky behind them. And because your corona was
likely much fainter on the edges of the band of light than at the center,
this also made it seem "narrower" even though you were magnifying it! Last,
about the colors: the human eye can only perceive colors at a certain light
level. Once the amount of available light falls below this threshold,
scotopic or "night" vision takes over, and we only see things in shades of
gray. By magnifying your corona, you apparently spread the light so thin
that your eyes could no longer pick up the pearly colors you had seen.

At least, THAT'S the conventional wisdom... ;> Hope this helps! But if it
raises more questions than it answers, then be sure to write back.

Clear skies (or hazy if you prefer :>),
Lew Gramer
dedalus@latrade.com