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Astro Imaging Where art, science, and education meet

Solar system

Jupiter

A two-color red-green image of Jupiter
A two-color red-green image of Jupiter.
(michael allen)

Transit of Venus

Transit of Venus taken through an Orion full aperture glass filter
2012-06-05, about 6:30pm Pacific Daylight TIme. Transit of Venus. Taken from the campus of Central Washington University in Ellensburg WA, on the lawn behind the computer science building. Telescope: Meade 90mm Maksutov-Cassegrain ETX-RA telescope, with an Orion Full Aperture Glass solar filter. Camera: Casio Exlim 10.1 Mpixel digital camera; Orion SteadyPix camera mount.
(michael allen)

Transit of Mercury

Transit of Mercury at third contact, or first egress point.
2016-05-09. Transit of Mercury, third contact point, seen from WSU; same set-up as the transit of Venus image. It had been totally overcast for about an hour and I worried that I would miss the end of the transit. The clouds parted. I snapped pictures as fast as my cheapie compact camera could and got this lucky shot.
(michael allen)

Moon

Earth's Moon
Earth’s beautiful Moon, taken 1-June-2023.
(michael allen)

Moon’s surface composition

Color imaging of the Moon can yield something of its immediate surface.  The image at left constructed from 3 images.  Each image was in a different filter: one centered on 656 nm (deep red), one on 502 nm (pale green), and one on 365 nm (ultraviolet).  The images were colored red, green, and blue, then aligned, then co-added to produce a RGB image. I balanced the colors to be as neutral as possible overall, which to my eye was similar to a chartreuse. Then I maxed the saturation, and increased the contrast slowly.  My attention was on the mare (the large round flat dark areas).  After several tries I came up with the final product.

Pictured is the northern hemisphere of the Moon.  To the left is Mare Imbrium, the “Sea of Rains”. To far left, the notch cut out of Mare Imbrium is Sinus Iridium, the “Bay of Rainbows”. At center is Mare Serenitatis, the “Sea of Serenity”. At lower right and attached to Serenity is Mare Tranquillatus, the “Sea of Tranquillity”. At far right is the isolated Mare Crisium, the “Sea of Crises”.

The colors in the Mare tell us of composition and history. The Maria formed from very large impacts between about 3 and 4 billion years ago; the Moon is 4.5 billion years old. Each impact left behind rings of mountains and a flat, fractured floor.  This floor forms what we call Iridium basin rock. It is formed mostly from surface material with a relatively high concentration of titanium compounds (higher than 7% by mass).  The reflected color of the rock takes on a purplish tinge.

Following the impact, liquid rock welled up and filled in the Maria floors. This rock is from the mantle, thus deeper below the surface and has less titanium (under 2%) and more iron. The reflected light is reddish. For example, Tranquillity is much more purplish than the others and thus is higher in titanuim content.

Isolated impact craters have a yellowish halo. At least some of this coloring is due to the formation of glassy structures at the moment of impact.

Reading:

Ronald Greeley, Planetary landscapes, 2e, New York, NY: Chapman & Hall, 1994.

John S Lewis, Physics and chemistry of the solar system, 2e, Amsterdam, NL: 2004.

Imke de Pater, and Jack J Lissauer, Planetary sciences, Cambridge, UK: CUP, 2001.

Links:

USGS unified geologic map of the Moon