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Earthshine and related optical phenomena
, The crescent Moon and its dark side. Right:
, Earthshine on the waning crescent moon.
Table of Contents
Earthshine and related optical phenomena
LPOD Photo Gallery
Earthshine photographs made during the last Apollo mission :
35 mm Nikon images made during Apollo 17
(contains lots of B-and-W Earthshine photographs of the moon's nocturnal western hemisphere!). Research Danny Caes.
Illumination of the Moon by sunlight reflected from the Earth. Just as the Earth receives light from the Moon, the Moon receives light from the Earth. However, the phases are complementary: that is, when the Moon is "full" as seen from the Earth, the Earth is dark as seen from the Moon, and vice versa. In addition, according to the NASA
Moon Fact Sheet
the Earth is 3.67 times larger (in radius) and about 3 times as reflective as the Moon. Since they are the same distance from each other this means that at any given phase the earthshine reaching the Moon is roughly 3.67²x3 = 40 times brighter than the moonlight we are accustomed to on Earth (actually somewhat more, since the moonlight we see has been attenuated by the Earth's atmosphere).
Bill Anders, one of the three astronauts of Apollo 8 (December 1968) commented on visibility of the lunar surface in Earthshine:
Earthshine is about as expected, Houston. Not as much detail, of course, as in the sunlight, but you can see the light craters quite distinctly, and you can see the albedo contacts quite distinctly. And, also, the - there's a good three-dimensional view of the rims of the larger craters.
Apollo 8 Journal
Many space-artists and illustrators have always made wonderful and mysterious looking paintings and drawings of lunar landscapes illuminated by the bluish Earthshine. Perhaps the most well-known examples of this sort of artwork are the extraordinary paintings made by Chesley Bonestell.
Two of those paintings are online in Fabio Femino's
website, on the fifth page dedicated to Chesley Bonestell (
the two panoramic paintings on top of that page
top painting on page 14
of Fabio's -Chesley Bonestell- retrospective shows a curious "rough" lunar landscape illuminated by yellowish solar light and bluish Earthshine. Note that such view was also captured by the
orbiter and the Japanese
second page of Fabio's -Collier's- retrospective
shows two Earthshine paintings near the bottom of that page. The upper one is the well-known painting of the manned expedition in crater
, illuminated by bluish/greenish Earthshine (floor of the crater) and yellowish sunlight (inner part of
' rim). The second painting shows a final departure, illuminated by bluish Earthshine.
Don Davis' painting of the Full Earth and sunlit lunar polar region
(which is a typical example of how the moon is illuminated by bluish Earthshine).
William K. Hartmann's painting of bluish Earthshine on a lunar crater's floor
(note the yellowish sunlight on the crater's opposite inner slope!).
(online search for Earthshine paintings to be continued...).
of january 1965 (page 127 of the article
The Making of an Astronaut
) Robert R. Gilruth described the possibility of an early manned lunar landing illuminated by Earthshine, not by direct sunlight. Page 226 of the
's february 1969 issue (the article
That Orbèd Maiden...The Moon
) shows a photograph of astronaut Don Lind while exercising at NASA's Manned Spacecraft Center to set out an ALSEP station, illuminated by dim bluish light. This photograph shows very well how a lunar landing would have looked like in earthshine.
Jan 13, 2011
Possible brightness enhancement of Earthshine caused by atmospheric optical effects known as the Primary Cloudbow and the Glory
) is a not well-known equivalent of the
, without vivid spectral colors. The cloudbow looks like a white diffuse circle with radius of about 40 to 45 degrees around the anti-solar point (180 degrees of the true sun). Although it is frequently observable on mountains surrounded by sunlit fog, or on clouddecks (from airliners above the clouds), few mountaineers and airliner-passengers seem to be familiar with it. Simultaneously appearing is the
, a multispectral colored effect at small angle around the anti-solar point.
Apr 29, 2009
Both optical effects (the
) could enhance the brightness of the Earthshine on the moon. The Cloudbow when the moon is at an angle of about 40 to 45 degrees of the sun, and the Glory when the moon is at very small angle of the sun (Full Earth).
Aug 3, 2008
The visibility of a bright lunar crescent with Earthshine at the moon's nocturnal part is
the same as a partial lunar eclipse!
Earthshine, shaky telescopes, and the Pulfrich effect
Observing both the moon's sunlit crescent and the nocturnal earthlit part through a small telescope with poor "shaky" mount (a weak tripod disturbed by wind) shows a remarkable example of the
! (a delay in the shaky movement of the earthlit part versus the sunlit crescent).
The Pulfrich effect is also noticeable in a partially eclipsed moon. Research Danny Caes.
The Pulfrich effect and double star observing
A curious example of the
was printed on pages 196-197 of T.W.Webb's
Celestial Objects for Common Telescopes, Volume Two: The Stars.
"This object, when near the meridian, will exhibit a phenomenon, noticed by Herschel: the pendulum-like oscillation of a small star in the same vertical with a large one, when the telescope is swung from side to side. This, he thinks, is due to the longer time required for a fainter light to affect the retina, so that the reversal of motion is first perceived in the brighter object. I have seen this strikingly in Delta and Zeta Orionis, and Delta Herculis".
See also page 167 of M.G.J.Minnaert's
Light and Color in the Outdoors
Oscillating Double Stars
Feb 12, 2011
- The same effect is noticeable at the open cluster NGC 2362 in Canis Major (aka
Tau Canis Majoris Cluster
), of which its brightest star (Tau CMA) is nicknamed "
Mexican Jumping Star
" because of its independent "jumping" against the background of the cluster's faint stars, whenever there's a little bit of shaking at the tube of the telescope.
Feb 12, 2011
This optical effect (the seemingly "large" sunlit crescent versus the "small" nocturnal earthlit part) is mentioned on pages 127-128 of M.G.J.Minnaert's
Light and Color in the Outdoors.
Feb 12, 2011
Bailly and the Dorfels (an interesting Earthshine-related observation by Harold Hill)
In Harold Hill's splendid book
A Portfolio of Lunar Drawings
there's an interesting telescopic observation of a shadowed (yet dimly illuminated) mountain range at the moon's south-southwestern limb, a mountain range which was once called
). On page 131 of that book, Mr.Hill added a drawing of what he observed during the nocturnal morning hours of september the 27th, 1951. It shows the Dorfel range with five sunlit peaks, and the lower part of the Dorfel's mass in a dim light, of which Mr.Hill thought it could have been Earthshine (at that day in 1951, the moon was at its
phase, and, as seen from the moon, the Earth should have been at
Now, could it (this weak illumination) have been a combination of Earthshine and reflected light of nearby sunlit slopes slightly east of the
Research Danny Caes.
Transit of the moon across the bright globular star cluster Messier 22 in Sagittarius
Are there observations and photographs of the moon's nocturnal part (First Quarter Moon/ Last Quarter Moon) made during the occultation of the thousands of stars in the core of the globular star cluster Messier 22? (the only bright globular cluster which is located slightly south of the ecliptic, on the moon's path).
May 17, 2015
New and Old Together
Sun, Moon and Stars
Two to One
A Smarter View
Two Views in One
Five to One
An Overlooked Gem
Why not Venus?
Yesterday's News (C0SMIC EDITION)
(J-P Metsavainio's rather "unusual" look at the moon and at the Earthshine)
The Last Dark Age
Milk of Plato
(an interesting observation by Phil Morgan, of possible
on the floor of
APOD's Search Results for -Earthshine-
: Twice reflected sunlight.
(2014). An Advanced Scattered Moonlight Model – ESO’s
section) - No 156, June 2014.
: Wikipedia article
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