Full Moon Handheld

Joseph Miller wrote:
Joseph Miller wrote:

First I apologize for adding an "e" to your name. I don't know why I did
that.

Second, with a little more time to read things, I realized that I was
putting words in your mouth. You never did say that the shadows at the
south pole were only a result of the moon not being full. I was mislead
by your making a point out the fact that the phase was not exactly full.
The fundamental trap I fell into was interchanging phase angle (a
technical term with a precise definition) and angle of phase- the
sun-earth-moon angle. The fundamental point remains. When you took your
picture the phase angle was well off zero, with a lot of it in a
north-south direction. The phase angle at full moon will be effectively
zero when the full moon is on the ecliptic (and an eclipse takes place),
but if the fulll moon is far from the ecliptic, a significant
north-south phase angle can be observed.

Joe,
No problem. Often people misunderstand each other in brief
exchanges on usenet. The challenge is not letting it deteriorate.

I do agree the apparent distance from the ecliptic plays a big role
in the shadows seen near full moon, but it is in reality
a little more complex. The Earth, for example is not always
on the ecliptic. The ecliptic is the mean orbital plane
and the Earth deviates from that plane a little due to
pull from other planets that are out of the plane. The mean
ecliptic is defined for some time, like J2000 is in common use.
Even the moon's orbit and the moon's inclination has an
effect.

http://www.bado-shanai.net/Astrogati...arthsorbit.htm

The full moon is defined as when the moon is 180 degrees
ecliptic longitude from the sun. But yes it can be above or below
the ecliptic. Thus the full moon can be less than 180 actual
degrees from the sun, and that is what is expressed in the phase angle.
Full moon usually is less than 180 degrees from the sun (lunar eclipses
are rare).

Then add another complication: where on the Earth you view the moon.
That varies by about 2 degrees.

So, adding the Earth's deviation from the ecliptic, the moon's
ecliptic latitude, and where and when you view the moon on the Earth
complicates simply using the moon's ecliptic distance for
predicting/explaining the shadows.
So, again, the phase angle gives the correct answer, especially
when computed for your exact time and location.

In the case of my lunar image, which was not at exact full moon,
that angular distance from 180 degrees ecliptic longitude adds
another factor in making the shadows, but that is accounted for
in the phase angle.

So, for you class, I suggest using your idea of the moon being out
of the ecliptic as a first approximation of the effect, but then
introduce phase angle and how it applies to everything we
observe around us (best ignore multiple light sources to start).
Then, you can predict for any situation, e.g. the view of the
moon from a spacecraft, or the view of a mountain and the setting sun,
what the shadows will be like. It works great for photographers
too.

Roger

Roger N. Clark (change username to rnclark) wrote:
No problem. Often people misunderstand each other in brief
exchanges on usenet. The challenge is not letting it deteriorate.

What did you just say about my momma?

(Roger*N.*Clark) wrote:

" The dark spots are not exposed bedrock. There is lunar dust everywhere
created by small meteor impacts, and is called a regolith. The dark
areas (mare) are different in composition and generally are relatively
younger basalt flows that erupted after the large impact basins were
formed. The lighter areas are called highlands because they generally
are higher. The mare basalts contain more pyroxene (a dark mineral with
lots of iron, thus called mafic), and the highlands contain relatively
more feldspar (a light mineral with little iron). "

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Care to try and explain why the 'not exposed bedrock but younger basalt
flows' are only located in a small part of the moon?

===================================




(Roger*N.*Clark) wrote:

" Yes, they are called crater rays. Rays are lighter in both the darker
mare and the lighter highlands mainly due to the fine particle size of
the smashed up rocks. "

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

AND those fine particles would be over every inch of the moon, if it
were as you say, since
the moon is hit incessantly by asteroids.

Instead it's only over the dark spots from
where recent asteroids have hit. (as the
rays show)

If your theory was correct, the 'mare' spots would have been covered
over a long time
ago.

wrote:
(Roger N. Clark) wrote:

" The dark spots are not exposed bedrock. There is lunar dust everywhere
created by small meteor impacts, and is called a regolith. The dark
areas (mare) are different in composition and generally are relatively
younger basalt flows that erupted after the large impact basins were
formed. The lighter areas are called highlands because they generally
are higher. The mare basalts contain more pyroxene (a dark mineral with
lots of iron, thus called mafic), and the highlands contain relatively
more feldspar (a light mineral with little iron). "

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Care to try and explain why the 'not exposed bedrock but younger basalt
flows' are only located in a small part of the moon?

===================================




(Roger N. Clark) wrote:

" Yes, they are called crater rays. Rays are lighter in both the darker
mare and the lighter highlands mainly due to the fine particle size of
the smashed up rocks. "

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

AND those fine particles would be over every inch of the moon, if it
were as you say, since
the moon is hit incessantly by asteroids.

Instead it's only over the dark spots from
where recent asteroids have hit. (as the
rays show)

If your theory was correct, the 'mare' spots would have been covered
over a long time
ago.

It is not my theory; it is results from the Apollo missions and
Earth-based telescopic work (using light to probe the
microstructure of the lunar soil).

See:
http://en.wikipedia.org/wiki/Regolith

http://www.meteorites.wustl.edu/luna...th_breccia.htm

The mare locations predominantly on the side facing the Earth
has been hypothesized as due to an asymmetry in the lunar crust
thickness and eruption of the mare basalts at thinner locations
in the crust. There are other explanations too, e.g.
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1984.pdf

Many moons and planets show hemispheric differences, even the
Earth (the Pacific ocean dominates one hemisphere).
Most moons are tidally locked due to asymmetries in their
mass distribution.

Roger

"Roger N. Clark (change username to rnclark)" wrote in
message ...
Saguenay wrote:
"Battleax" a écrit dans le message de news:
...

Sure, you'll prefer this 500mm NOT handheld:
http://baron.phpnet.us/50-500/crw_05...?size=1&exif=Y

(a few days before)...

Saguenay
Very nice image. But you'll just make the troll more jealous.

Roger

Troll? I think that it would appear that he was quite correct from this
demonstration, why call him a troll.

"Roger N. Clark (change username to rnclark)" wrote in
message ...
Battleax wrote:
"Roger N. Clark (change username to rnclark)" wrote
in message ...
I finally had a night with a steady atmosphere, so I
tried imaging the full moon handheld at 1000 mm (real focal length):

http://www.clarkvision.com/galleries...3f-8s-800.html

This was done standing up with no supports and not leaning against
anything.
The full resolution image can be seen from the above page.

Roger


Over exposed, lost detail. Just another unremarkable moon shot I'm
afraid. The fact that it is hand-held is completly irrelevant
Wrong. Not one pixel is saturated.

That fact does not make it properly exposed. See the far better exposed shot
further up in the thread, much better.

Pete D wrote:

http://www.clarkvision.com/galleries...3f-8s-800.html
Over exposed, lost detail. Just another unremarkable moon shot I'm
afraid. The fact that it is hand-held is completly irrelevant
Wrong. Not one pixel is saturated.

That fact does not make it properly exposed. See the far better exposed shot
further up in the thread, much better.

1) there is no other full moon image further up the thread.

2) On my calibrated monitors I can see detail in the brightest
parts of the image, as well as darkest, and everywhere in between.

3) The full moon appears very bright to both the unaided eye
and through a telescope, and the image gives that impression,
the exact effect I was trying for.

Roger