Earthshine

[JamesF]

I tend to see Earthshine when the Moon is low in the western sky. Is this:

1) Because I've been unlucky

2) Just the way it works

3) Because the Atlantic Ocean reflects sunlight onto the Moon much better than Russia and Asia

4) For some other reason, and if so, what?

James

[Paul M]

Imagine if you were on the moon looking back at earth at that same time.

As the moon is low in the west at sunset it implies that from the moon you will be looking on to mostly Sunlit Earth. Therefore maximum earth shine.

It follows then that you get most earthshine when the moon is the thinnest crescent. Actually if you stood on the earthward side of the New Moon you'd be looking back at a "full" earth.

At full moon you's be looking at a "new" Earth.

Half moon, you'd see a "Half" Earth.

The nearer the moon is to new the more the more of the earth facing it is illuminated thus reflects back more light = more Earth shine.

[JamesF]

But if it happens when the Moon is low in the west soon after sunset, can it not happen if the Moon is low in the East shortly before sunrise?

James

[JamesF]

I realise I missed an implied part of my original question out. That is, I tend to see Earthshine when the Moon is low in the western sky, but haven't noticed it when the Moon is low in the eastern sky.

James

[Paul M]

But if it happens when the Moon is low in the west soon after sunset, can it not happen if the Moon is low in the East shortly before sunrise?

James

Yup, it can and does.

Clouds produce the greater part of Earth albedo/reflectivity. So most of the variation in the intensity of Earth shine would be down to the degree of cloud cover on the moonward side of Earth. That, on a hemispheric scale probably doesn't vary very greatly.

But anyway, you should see earthshine in the mornings too.

[JamesF]

I guess I've just been unlucky then. Not that my lack of luck might have anything to do with an inability to get out of bed early in the morning

James

[Paul M]

I guess I've just been unlucky then. Not that my lack of luck might have anything to do with an inability to get out of bed early in the morning

James

TBH, I'm not aware of any real difference between dawn or dusk earthshine intensity. Perhaps a cloudy atlantic does reflect back light than the bare deserts of the middle east?

But morning earthshine is certainly there. I've seen it!

[cantab]

Not that my lack of luck might have anything to do with an inability to get out of bed early in the morning

Seems the likely explanation to me. Most of us through much of the year will get up after sunrise and stay up until after sunset.