I was out on my porch, looking at the crescent moon, and I can see the entire disc, not just the thin, lit part. I know that is because the rest is lit from the light reflecting off of the Earth-Earthshine. My question is, if it is possible to see the New Moon, as a dark disk, solely lit from Earthshine.
During a total eclipse of the moon it is possible to see the entire moon. WAG - It should be possible to see the new moon if you know where to look.
I rather doubt it, and I’ve never heard of anyone reliably reporting it. The only time the New Moon is in the sky is during the day, when whatever faint light illuminating the Lunar surface from Earthshine would be washed out by the light of the sky.
A perfect “new moon” is only possible during a total solar eclipse, i.e. the moon is positioned precisely between you and the sun. Undoubtedly there is earthshine on the moon’s surface, but it is outshone by the sun’s corona (or by the edge of the sun, in an annular eclipse).
What you’re seeing, in that case is, the sum of the ‘ring’ around the Earth, of all the sunrises and sunsets going on at that time.
Yes, but the contrast in that photo has been manipulated to bring out the features of the moon. In reality, during a total solar eclipse, the moon and the surrounding sky appear black.
Oh sure, it’s 28 images spliced together to get a very high dynamic range.
I just wanted to show that there is earthshine during an eclipse.
If you were in orbit and were able to see a solar eclipse you might be able to see the earthshine.
The question would be, is the solar corona bright enough to ruin you night vision enough that the earthshine would be too faint?
A WAG: if the separation of the moon and the sun was at maximum during the new moon (during a solar eclipse of course they are at minimum separation), and you were at a location on the earth where the sun disappeared below the horizon first during the sunset (or the moon rose before the sun in the morning), you might (might) have a shot if you knew where to look, probably needing some binocs or a 'scope to see it. Would be a very thin crescent…
From earth, the corona is very bright. From orbit, it would depend on the height of the orbit. Low enough, and you’d see the eclipse pretty much as on earth. High enough, and you wouldn’t see the corona at all, and would definitely see features of the moon.
Even without an eclipse, you would see some features of the “dark side” of the moon, if only by starlight. Of course you’d see more if there’s earthlight too.
I doubt it. People compete to set records for “young moon sighting”, and the record (unless it has been broken since this was written) is for a twelve-hour-old moon with an ecliptic longitude separation of 7.7 degrees from the Sun. Since the moon was north of the ecliptic at the time, I assume that the actual sky separation would have been a little greater.
The greatest possible sky separation between the Sun and a new moon is 5.1 degrees.
To be sure, in the middle latitudes some of the separation is “wasted” because Sun and moon set at an angle. You might stand a better chance at the Poles, where five degrees of right ascension separation (at an optimal new moon) translates into five degrees of azimuth separation. In the clear dry air at the South Pole, if there were a new moon to the south of the ecliptic, just after the March equinox or just before the September equinox . . . it might just be possible. I’m not aware that anyone has ever made the attempt.
In any case, you’d be hunting the thin crescent, not the earthshine. To answer the OP, no it is not possible to see an entirely earthlit moon, except during a total eclipse. If the moon is so close to the Sun that the lit crescent becomes invisible, then it’s too close to the Sun to have any chance to view the earthshine.
Its actually 2 problems.
Can you “see” a moon that has ONLY earthshine? With no lit cresent.
Yes, probably IMO, in extremely favorable or unique settings, as you or others described.
And , in those situations, would the earthshine actually be bright enough to see and/or would other contributing factors make it easier or harder to see?
Yes, again IMO.