P3D Re: Moon Size

[Larry Berlin <lberlin@xxxxxxxxx>]

> Date: Sat, 15 Jan 2000 
> From: koganlee@xxxxxxxxxxxxx
> .........
> >Besides, there is a very real size difference between a horizon moon and
> >the elevated moon. The so called illusion may exist too, but it's not
> >the only factor by a long ways. Over many years of watching the full
> >moon rise above the horizon, I have watched the apparent size of the
> >moon change while there is still reference landscape easily within view. 
> >
> 
> Larry,
> 
> It's one thing to look at the moon and sense its apparent size. It is another to actually measure the moon as it rises. I
> have made several 
> images (they happen to be stereo, but it makes no difference) of the moon at 5 minute intervals as it rises from the
> horizon. The size of the 
> moon is certainly no bigger at the horizon than it is higher in the sky. (On the film it actually looks ever so slightly
> bigger as it gets 
> further from the horizon, but that is because objects appear slightly larger as they move off the center of the lens axis.
> To do a 
> really accurate test, one would have to re-center the moon and shoot it on subsequent frames.) I'll be happy to send one of
> these images to 
> anyone who would like to see for themselves.
> 
> David Lee
> 

Well, for argument's sake it would be interesting to see your images. It
would also be good to see the data which scientists elsewhere have used
to describe the refraction effect of the atmosphere with low incident
angles of view. It happens to the Sun and the Moon. Whether or not you
can obtain sufficient resolution on frames of film to determine the full
story is uncertain.

IF this notion were true, why then does the moon not seem magnified
while high in the sky simply by stepping under the branches of a tree?
Does that not provide the local reference factor to which they attribute
their data? Yet, the moon doesn't appear to change size even a tiny bit
with the presence of local references. Yet the enlargement at the
horizon is quite strong, and it does appear to change in reference to
distant reference points that remain visible as the moon lifts. At what
point illusion steps in and takes over from refraction, I don't know
because I haven't tried to actually measure the effect.

Further, they start by stating that the moon near the horizon seems
farther away because of the landscape reference nearby. Yet it's
precisely the opposite in my life long experience, and I have yet to
meet ONE person who doesn't have the -impression- of the moon being
closer at the horizon than when up in the sky. Precisely the opposite of
the basis of their argument.

When the moon rises over mountains instead of a flat horizon like an
ocean, the enlarged effect isn't there. Yet according to their theory it
should be equally present. It isn't. The difference? Atmosphere.
-- 
Larry Berlin

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