Question: Different Size and redish tent of the Moon

"David Knisely" wrote...
in message ...

Hi there Darrel. You posted:

Can someone explain why at certain times the Moon looks redish in color, low
on the horizon, and appears to be much larger?

The moon appears more reddish when it is low towards the horizon due the the
Earth's atmosphere. It reddens the moonlight, scattering the shorter
wavelengths more away from your viewing direction but allowing the longer
(redder) wavelengths to come to you more directly. However, the true angular
size of the moon is actually just a tiny bit *less* when it is low on the
horizon than it is when it is nearly overhead, because we are just a little
farther away from it when it is on the horizon. The "enlarging" effect you
refer to is known as "the Moon Illusion", and is just that, a mere illusion.
When the moon is low, you can see other objects to compare it to, but when it
is overhead, there is little next to it for comparison. It is this difference
which makes the moon seem to be a little larger towards the horizon that it
does when it is overhead, even though it isn't all that much different in true
angular size. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

'Lo David and Darrel --

So the Ponzo Illusion is out? Is this no longer an accepted
alternate explanation for the large appearance of the Moon
on the horizon?

http://www.sandlotscience.com/Distor...Ponzo_java.htm

I think our minds just see the Moon overhead as being so
much farther away, and therefore smaller, than when it's on
the horizon.

As noted the difference is pretty significant. If the average
distance to the Moon (center of Earth to center of Moon) is
239,000 miles, then the Moon's distance from an observer
when it's high in the sky is decreased by the radius of the
Earth, or to about 235,000 miles. At this time the Moon is
closer and OUGHT to appear LARGER than when it's on
the horizon.

The figure is 1.7%... so while the Moon *seems* to be so
much bigger when it's near the horizon, it's *actually* 1.7%
smaller than when it's high in the sky.

happy days and...
starry starry nights!

--
Sometimes OH! my mind grips a thought so unkind
That it twists me to heights of contortion...
I'm often so glad that my mom and my dad
Didn't follow along with abortion!

Paine Ellsworth

"David Knisely" wrote...
in message ...

Hi there Darrel. You posted:

Can someone explain why at certain times the Moon looks redish in color, low
on the horizon, and appears to be much larger?

The moon appears more reddish when it is low towards the horizon due the the
Earth's atmosphere. It reddens the moonlight, scattering the shorter
wavelengths more away from your viewing direction but allowing the longer
(redder) wavelengths to come to you more directly. However, the true angular
size of the moon is actually just a tiny bit *less* when it is low on the
horizon than it is when it is nearly overhead, because we are just a little
farther away from it when it is on the horizon. The "enlarging" effect you
refer to is known as "the Moon Illusion", and is just that, a mere illusion.
When the moon is low, you can see other objects to compare it to, but when it
is overhead, there is little next to it for comparison. It is this difference
which makes the moon seem to be a little larger towards the horizon that it
does when it is overhead, even though it isn't all that much different in true
angular size. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

'Lo David and Darrel --

So the Ponzo Illusion is out? Is this no longer an accepted
alternate explanation for the large appearance of the Moon
on the horizon?

http://www.sandlotscience.com/Distor...Ponzo_java.htm

I think our minds just see the Moon overhead as being so
much farther away, and therefore smaller, than when it's on
the horizon.

As noted the difference is pretty significant. If the average
distance to the Moon (center of Earth to center of Moon) is
239,000 miles, then the Moon's distance from an observer
when it's high in the sky is decreased by the radius of the
Earth, or to about 235,000 miles. At this time the Moon is
closer and OUGHT to appear LARGER than when it's on
the horizon.

The figure is 1.7%... so while the Moon *seems* to be so
much bigger when it's near the horizon, it's *actually* 1.7%
smaller than when it's high in the sky.

happy days and...
starry starry nights!

--
Sometimes OH! my mind grips a thought so unkind
That it twists me to heights of contortion...
I'm often so glad that my mom and my dad
Didn't follow along with abortion!

Paine Ellsworth

"David G. Nagel" wrote...
in message ...

The large appearance of the moon when it is low on the horizon is pure
optical illusion. If you look through a window at moon rise and make a
mark then as the moon rises make another mark as it clears the previous
mark you will see that it does not change size. As to the reddish tint
that is caused by air pollution, pure and simple. This condition has
exhausted for as long as the moon has exhisted. Today the pollution is
mostly caused by man but nature contributes is share also.

Dave Nagel

'Lo Dave --

You may want to rethink your answer for the reddish tint
of the Moon. In your research, try finding out more info on
why the Sun and sunsets often appear reddish to us. For
when the Moon is low in the sky, its reflected light is red
or orange for the same reasons.

hth

happy days and...
starry starry nights!

--
God! i hope so very deep
That if there is a Heaven,
All the people traveled there
Who died on Nine/Eleven,

And all the people in the world
Who spread great hate as well.
But yet i fear that haters shall
Most surely boil in Hell.

Paine Ellsworth

"David G. Nagel" wrote...
in message ...

The large appearance of the moon when it is low on the horizon is pure
optical illusion. If you look through a window at moon rise and make a
mark then as the moon rises make another mark as it clears the previous
mark you will see that it does not change size. As to the reddish tint
that is caused by air pollution, pure and simple. This condition has
exhausted for as long as the moon has exhisted. Today the pollution is
mostly caused by man but nature contributes is share also.

Dave Nagel

'Lo Dave --

You may want to rethink your answer for the reddish tint
of the Moon. In your research, try finding out more info on
why the Sun and sunsets often appear reddish to us. For
when the Moon is low in the sky, its reflected light is red
or orange for the same reasons.

hth

happy days and...
starry starry nights!

--
God! i hope so very deep
That if there is a Heaven,
All the people traveled there
Who died on Nine/Eleven,

And all the people in the world
Who spread great hate as well.
But yet i fear that haters shall
Most surely boil in Hell.

Paine Ellsworth

Painius wrote,

...then the Moon's distance from an
observer when it's high in the sky is
decreased by the radius of the Earth....

That's true at Earth's equator. At increasing latitudes N and S, the
difference becomes progressively less.
oc

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Painius wrote,

...then the Moon's distance from an
observer when it's high in the sky is
decreased by the radius of the Earth....

That's true at Earth's equator. At increasing latitudes N and S, the
difference becomes progressively less.
oc

Anti-spam address: oldcoot88atwebtv.net
Change 'at' to@

"Bill Sheppard" wrote in message...
...

Painius wrote,

...then the Moon's distance from an
observer when it's high in the sky is
decreased by the radius of the Earth....

That's true at Earth's equator. At increasing latitudes N and S, the
difference becomes progressively less.
oc

Anti-spam address: oldcoot88atwebtv.net
Change 'at' to@

I see what you mean, Bill... the 1.7% would be a maximum
possible difference based upon the observer being in a
place where the distance to the Moon decreases by the
entire radius of the Earth as the Moon rises from horizon to
zenith.

However, since the Moon can be as much as 18 degrees
off the equator, would there not be a window of changing
latitudes that would be at maximum distance in different
cycles?

happy days and...
starry starry nights!

--
Life without love is
A lamp with no oil,
Love without prejudice
A world with no soil,
A tool with no toil.

Paine Ellsworth

"Bill Sheppard" wrote in message...
...

Painius wrote,

...then the Moon's distance from an
observer when it's high in the sky is
decreased by the radius of the Earth....

That's true at Earth's equator. At increasing latitudes N and S, the
difference becomes progressively less.
oc

Anti-spam address: oldcoot88atwebtv.net
Change 'at' to@

I see what you mean, Bill... the 1.7% would be a maximum
possible difference based upon the observer being in a
place where the distance to the Moon decreases by the
entire radius of the Earth as the Moon rises from horizon to
zenith.

However, since the Moon can be as much as 18 degrees
off the equator, would there not be a window of changing
latitudes that would be at maximum distance in different
cycles?

happy days and...
starry starry nights!

--
Life without love is
A lamp with no oil,
Love without prejudice
A world with no soil,
A tool with no toil.

Paine Ellsworth

Painius wrote,

However, since the Moon can be as
much as 18 degrees off the equator,
would there not be a window of changing latitudes that would be at
maximum
distance in different cycles?

Why sure, it'd give a window, just as the moon's own libration gives us
little peeks beyond the lunar horizon monthly. oc

Anti-spam address: oldcoot88atwebtv.net
Change 'at' to@

Painius wrote,

However, since the Moon can be as
much as 18 degrees off the equator,
would there not be a window of changing latitudes that would be at
maximum
distance in different cycles?

Why sure, it'd give a window, just as the moon's own libration gives us
little peeks beyond the lunar horizon monthly. oc

Anti-spam address: oldcoot88atwebtv.net
Change 'at' to@