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Author Topic: Earth Eclipse as seen from the Moon?  (Read 1257 times)

Offline dan@frankdan.com

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Earth Eclipse as seen from the Moon?
« on: 05/10/2014 17:12:30 »
Iím wondering - Could Chang'e 3 Lander photograph Earth as we experience the lunar eclipse on October 8?

Of course, from the moon, it would be the Earth eclipsing the sunÖ

It seems there would be much to be learned, as well as documenting a phenomenon never before seen.

Perhaps itís much too dangerous for the optics, but I would love to see that image.

Bonus question: From the moon, would the earth just hover in the same spot in the sky all the time, with the sun crossing the sky in a 28-day "day"?


 

Offline evan_au

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Re: Earth Eclipse as seen from the Moon?
« Reply #1 on: 06/10/2014 07:01:11 »
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Could Chang'e 3 Lander photograph Earth as we experience the lunar eclipse on October 8?
Yes, that would work. However, a lander is likely to have optics intended for examining nearby terrain in detail, rather than the telescopic optics which would be best for studying the Sun.

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Of course, from the moon, it would be the Earth eclipsing the sunÖ
Yes. What makes eclipses of the Sun so interesting (as seen from Earth) is that the Sun and the Moon have roughly the same angular diameter as seen from Earth. This means that the Moon can hide the entire visible disk of the Sun, while leaving the Sun's tenuous atmosphere (the corona) visible.

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It seems there would be much to be learned, as well as documenting a phenomenon never before seen.

Unfortunately, from the viewpoint of the Moon, the Earth fills a much larger part of the sky than the Sun, so you won't get to see the full circle of the Sun's corona. Dedicated Sun-watching space probes using an instrument called a coronograph will reveal more than Chang'e can tell us.

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Perhaps itís much too dangerous for the optics, but I would love to see that image.
The optics would be optimised for the dark/greyish lunar soil, rather than very bright sunlight.
Just as you should never stare at the Sun,  Chang'e should not, either.

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Bonus question: From the moon, would the earth just hover in the same spot in the sky all the time, with the sun crossing the sky in a 28-day "day"?
Yes, due to the Moon being "tidally locked" to the Earth, the Earth spins in roughly the same spot in the Moon's sky, with some small movement due to the elliptical nature of the Moon's orbit, and tugs from the Sun.
 

Offline dan@frankdan.com

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Re: Earth Eclipse as seen from the Moon?
« Reply #2 on: 06/10/2014 14:13:33 »
Thanks for the response. I still think there might be something to learn from viewing an "Earth eclipse" from the moon - not necessarily about the sun's corona, but about the earth's atmosphere and the effects of the sun.

And we'd see why the moon looks so red-orange from the earth during and eclipse. All those sunsets and sunrises at once! I admit, my interest is mostly aesthetic, but there might be a trace of science to be gleaned...
« Last Edit: 06/10/2014 14:18:33 by dan@frankdan.com »
 

Offline evan_au

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Re: Earth Eclipse as seen from the Moon?
« Reply #3 on: 06/10/2014 21:08:38 »
I guess seeing Earth surrounded with a thin halo of light would be interesting to see.
It might bring an awareness of the finite capacity of our atmosphere.

...In the past, it was thought that the solution to pollution was dilution (from a recent book I read recently).
 

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Re: Earth Eclipse as seen from the Moon?
« Reply #3 on: 06/10/2014 21:08:38 »

 

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