Starship Asterisk*

by **thebobgy** » Thu Sep 20, 2007 4:07 pm

Chris Peterson wrote:
ruidh wrote:Actually, I'm more interested in this sentence from today's APOD. "The Moon was up continuously for 14 days in August -- when viewed from the South Pole."
But the Moon makes a complete orbit every month. So the Sun is invisible half of each year, and the Moon is invisible about half of each lunar month.

Chris, Would the Lunar effects be the reverse at the North Pole? Thanks.

Bob Smith

by **pandanuma** » Sun Sep 09, 2007 7:49 am

thanks

by **Chris Peterson** » Sat Sep 08, 2007 5:05 am

Case wrote:
Chris Peterson wrote:It will be different stars from Canada.
Only a little bit: the difference is under 3°; the Moon stayed in Aquarius.

Yes, but the pictures are oriented with respect to the horizon. So what's above the Moon in Canada is below it in Antarctica. The stars seen above the Moon are in completely different constellations in the two images. You can see the effect of the different latitudes in the images- from Antarctica, the eclipsed Moon is moving from right to left, with the Earth's shadow moving in from below. From Canada, it is moving left to right, with the shadow entering from above. If you flip one of the images upside down, you can match a few of the star tracks (that is, stars over the Moon in the Antarctic with stars under it in Canada).

by **Case** » Sat Sep 08, 2007 4:31 am

Chris Peterson wrote:The object at the far left above the Moon, caught on just a few frames, might be Jupiter.

According to Stellarium, Jupiter must have left the field of view about two hours before the first frame was taken. Also the brightness isn't enough, as Jupiter (-1.78) would out-shine the magnitude 1 and 2 stars in this view.

Chris Peterson wrote:It will be different stars from Canada.

Only a little bit: the difference is under 3°; the Moon stayed in Aquarius.

by **Chris Peterson** » Fri Sep 07, 2007 10:18 pm

pandanuma wrote:The south pole and kalamalka lake eclipse photos both show numerous other objects tracking through the sky.

What are these objects?
If they are other celestial objects, why do they seem to mirror the same arc of travel as the moon?

(my own guess...as the world turns the objects in the distance appear to move in the same proportion??)

They are stars. It's hard to tell exactly which without a detailed analysis. In the South Pole image, they are probably components of Sagittarius, Capricornus, and Cetus. The object at the far left above the Moon, caught on just a few frames, might be Jupiter. It will be different stars from Canada.

You are correct about why they seem to follow the same path as the Moon. If you look closely enough, they don't quite, because the Moon moves at a slightly different rate. But over the several hours of the eclipse, the difference isn't very great.

by **Case** » Fri Sep 07, 2007 10:15 pm

pandanuma wrote:What are these objects?

Very observant of you to notice these (I missed them)!
They'd have to be stars. With a star chart of the corresponding time, you could even identify them (stars from Capricorn and Aquarius). Neptune and Uranus were also in the vicinity of the moon at that time, but I doubt they're bright enough to show up on the photo.

In the short period of the composite photo (3 hours or so) the moon seems stationary to the celestial objects, so during that time they all rotate around the position of Polaris (northern hemisphere) or it's Antarctic counterpart (southern hemisphere), because of the Earth's rotation.
See also "star trails".

by **pandanuma** » Fri Sep 07, 2007 9:07 pm

The south pole and kalamalka lake eclipse photos both show numerous other objects tracking through the sky.

What are these objects?
If they are other celestial objects, why do they seem to mirror the same arc of travel as the moon?

(my own guess...as the world turns the objects in the distance appear to move in the same proportion??)

by **Case** » Fri Sep 07, 2007 2:32 pm

ruidh wrote:The Sun isn't continuously visible because the axis of rotation of the Earth is tilted with respect to it's plane of revolution around the Sun.
But, I would have expected that the moon's plane of rotation around the Earth is not tilted very much with respect to the axis of Earth's rotation.

I believe the moon orbits around the earth approximately in the same plane as the earth orbits around the sun, with no relation to the axis of rotation of the earth itself. Because that is the only position in which it is possible to see the phase of a full moon. If the moon orbited the earth along the earth's equator, then some portion of the moon's disk would always be unlit, when viewed from earth.
So, sort of like the never-setting summer-sun, the moon will be visible for a long period (half a month?), day and night, from polar regions.
Also, the moon has to orbit exactly across the sun-earth plane, with all three in a row, to make eclipses possible. If the moon's orbit was equatorial, then that could only happen at the beginning of spring and autumn.

by **Chris Peterson** » Fri Sep 07, 2007 2:25 pm

ruidh wrote:Actually, I'm more interested in this sentence from today's APOD. "The Moon was up continuously for 14 days in August -- when viewed from the South Pole."

Why isn't the moon continuously visible from the South Pole?

The Sun isn't continuously visible because the axis of rotation of the Earth is tilted with respect to it's plane of revolution around the Sun.

But, I would have expected that the moon's plane of rotation around the Earth is not tilted very much with respect to the axis of Earth's rotation.

What is the inclination?

The Moon's orbit is inclined about 5° to the ecliptic. That means it varies from about 18° to 28° with respect to the equator. Even if it was directly on the ecliptic, however, it still wouldn't be visible all winter from the South Pole. Even in winter, a good part of the ecliptic is always above the horizon. The Sun isn't seen because the part of the ecliptic it's on is below the horizon. But the Moon makes a complete orbit every month. So the Sun is invisible half of each year, and the Moon is invisible about half of each lunar month.

by **ruidh** » Fri Sep 07, 2007 1:56 pm

Actually, I'm more interested in this sentence from today's APOD. "The Moon was up continuously for 14 days in August -- when viewed from the South Pole."

Why isn't the moon continuously visible from the South Pole?

The Sun isn't continuously visible because the axis of rotation of the Earth is tilted with respect to it's plane of revolution around the Sun.

But, I would have expected that the moon's plane of rotation around the Earth is not tilted very much with respect to the axis of Earth's rotation.

What is the inclination?

by **IGAT** » Thu Sep 06, 2007 2:11 pm

NoelC wrote:I've heard that there's an outer layer of Ozone that refracts blue-green light (obviously at a lower level than the red)

Thank you. Certainly, I found a blue-green layer of atmosphere in some pictures taken from space, like this.
http://antwrp.gsfc.nasa.gov/apod/ap981024.html

But, at present, I can't tell if one can see those blue-green light from lunar surface in mid-eclipse.
As you write, I think that the red light will be much stronger than blue-green light.
(Similarly, I think thant anyone can't see any stars near the Earth's shining red ring.)

I've seen many photos of sunset or sunrise taken from space.
But I couldn't believe those atmospheric scuttering lights could shine on the moon into such a red color in that lunar eclipse.
Unfortunately,there seems to be no photos of solar eclipse taken from lunar surface.
So, is there any pictures of the Earth's atmosphere that seems to be able to make the moon reddened?
(In case you didn't know, I don't forget the first question of this thread.)

by **NoelC** » Mon Sep 03, 2007 4:21 pm

People weren't as educated 50 years ago. We didn't have all this wonderful information and imagery the Internet affords us. Not to mention the fact that few regular folks had telescopes and cameras capable of shooting a sharp moon image during an eclipse back then.

It's quite amazing how far we've come in such a short time.

In all recorded history sunsets have been red, so we can be sure a red colored moon during eclipse isn't anything new.

Igat, I've heard that there's an outer layer of Ozone that refracts blue-green light (obviously at a lower level than the red), but you might want to go do some more research on this to verify it.

Also, you might want to add a few stars to your renderings to increase the artistic impact.

-Noel

by **IGAT** » Mon Sep 03, 2007 4:03 pm

I made a few measurements off the images I took during the eclipse, and it appears that the surface brightness of the Moon was about 1000 times reduced at mid-eclipse.

Thank you very much for your measurement result, and advice to my rendering.

According to your data, the Earth's atmospheric scattering light is sure to shine by the brightness of 1/1000 of the sun.
Apparent magnitudes of the full moon is −12.6, and the sun's is −26.7, and the ratio of the brightness is about 1/500000.
So, at mid-eclipse, the Moon is shoned on by the Earth's atmosphere by the brightness of 500 times of full moon seen from earth.
...Do you think that my calculation is correct?

With your advices, I made a few images.

http://igabigmoon50.mo-blog.jp/iron/

by **Chris Peterson** » Mon Sep 03, 2007 1:40 pm

SmartAZ wrote:Maybe someone can explain something to me. Everyone seems to think a red moon is expected during an eclipse, even old hat. But when I saw one in the early 50s it was quite unexpected and it took a while for someone to figure out why it looked red. The newspaper said nobody had seen that effect before.

Is this a new effect, only seen in the last fifty years?

It's hardly a new effect- maybe it was new to the author of the article, and maybe it took him a while to find somebody who could explain the color.

by **SmartAZ** » Mon Sep 03, 2007 7:08 am

Maybe someone can explain something to me. Everyone seems to think a red moon is expected during an eclipse, even old hat. But when I saw one in the early 50s it was quite unexpected and it took a while for someone to figure out why it looked red. The newspaper said nobody had seen that effect before.

Is this a new effect, only seen in the last fifty years?

by **Chris Peterson** » Fri Aug 31, 2007 4:04 pm

IGAT wrote:But, actually, how strong is the brightness?
I'd like to know that if there is observed data.

I made a few measurements off the images I took during the eclipse, and it appears that the surface brightness of the Moon was about 1000 times reduced at mid-eclipse.

Your rendering is very attractive, but if you want it to be more realistic, I'd say you need to eliminate the diffuse red glow around the Earth, leaving just the thin red line of red marking the atmosphere. You should probably also desaturate the red of the lunar surface. Finally, since you are showing a bit of the Sun peaking out, you would be at the shadow's edge on the Moon. I doubt you would see the surface as anything other than its usual neutral color, and the glare of the Sun would probably make the atmospheric scatter invisible. As with a solar eclipse viewed from Earth, a lunar eclipse viewed from the Moon is probably pretty unimpressive until the Sun is entirely obscured.

by **IGAT** » Fri Aug 31, 2007 2:18 pm

Here is an another image I made.

http://igabigmoon50.mo-blog.jp/iron/

During soloar eclipse by the Earth, the Moon must be shone by strong red light through Earth's atmosphere, I think.

But, actually, how strong is the brightness?
I'd like to know that if there is observed data.

by **Pete** » Thu Aug 30, 2007 9:34 pm

Well understood, maybe, but as you so mordantly pointed out, never actually observed

Here's a 2002 APOD composite of what an eclipse might look like from the Moon: http://apod.nasa.gov/apod/ap070302.html

For a computer-generated video of an eclipse of the Sun by the Earth seen from the Moon, check this out: http://elektronkind.org/video/aug28lunecl-moon.mp4

by **Case** » Thu Aug 30, 2007 8:17 pm

1/ NASA wouldn't have posted an sf story if they had the real thing.
2/ None of the manned lunar landings were during eclipses.
3/ The unmanned lunar landings were for real science, not for pretty pictures of well understood phenomena.

by **Petermurraynator** » Thu Aug 30, 2007 5:07 pm

Are there any photos from the moon's surface of what would be a solar eclipse by the earth? Please provide a link. thank you.

Starship Asterisk*

Lunar Eclipse (APOD 30 August 2007)

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