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Copernicus and Montes Riphaeus
On Monday January 9, between 16.00 hrs UT an 18.00 hrs UT, I observed a nine-day-old Moon and shot a few images of different parts of the lunar landscape. I used the TAL 200K combined with various eyepieces to observe the Moon visually. The eyepieces ranged from a 32m Televue Plossl to a 5mm Vixen Lanthanum.

For me, the most interesting features imaged were Clavius (previously published in this blog), Copernicus and Montes Riphaeus, and finally the Plato area (will be published in the near future). I used the Nikon coolpix 4500 and a 20mm Vixen Lanthanum eyepiece combined with a Baader IR/UV cut filter for the overview image of the Copernicus-Riphaeus area (images 2 and 3).

Image 1: Overview of a nearly full Moon

On the image above, an overview image of a nearly full Moon (which I shot in August 2004 with the TAL 100RS mounted on a photo-tripod!), the transparent yellow patch represents the area that you is shown on overview image 2 and 3. Image 1 his been severely processed, to emphasize the contrast between the Maria and the Terrae.

Maria and Terrae

Roughly, the lunar landscape can be divided in two types of surface, the dark areas known as Maria and the light areas known as Terrae. The Maria, or seas, are the grey smooth plains on the lunar surface. The Terrae, also known as highlands or uplands, are the bright and rugged areas of the Moon, full with craters, mountain-ridges and other interesting features. But why are they called Maria and Terrae?

In the year 1609, Galileo was the first person to look at the Moon with a telescope. Galileo concluded from his observations that the Moon's geography was not so different from our earth. He saw mountains, valleys and plains. Mistakenly he thought that the dark smooth areas he saw were oceans. That's why he called them Maria (Latin for seas). The brighter parts, a much more rugged terrain, were called Terrae (Latin for lands). In reality however, the Maria tend to be the lowland and the Terrae the highland.

Copernicus-Riphaeus area
Before we take a closer look at Copernicus, I would like to point out a few other interesting features that can be seen on the images 2/3. Lets start in the Southwest with Montes Riphaeus and Euclides (Rukl 40/41). Tonight this isolated mountain range was visible near the terminator. The formation immediately drew my attention because of its distinct form. Together with the southwestern rim of Euclides P it looked like a starfish with the crater Euclides at its centre. Euclides is a young, simple impact crater with a very sharp and well-defined rim. Its diameter is 12km. In stark contrast with this young crater is the old crater Euclides P, which lies to the north of Montes Riphaeus, on the shores of Mare Insularum. The crater almost completely vanished beneath dark Mare material. The tip of the arrow that points out Euclides P touches the southwestern rim of the crater.

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Images 2 and 3, Copernicus and Montes Riphaeus area (click to enlarge)

To the northeast of Euclides P lies the Apollo 12 landing area. To the East of the Montes Riphaeus, in the hills north of Fra Mauro (Rukl 42) you can see the Apollo 14 landing place. Between Reinhold and Copernicus (Rukl 31) lies the double-crater Fauth and Fauth A. Together they are shaped like a keyhole. On the Apollo 12 image (image 5) you can see Fauth-Fauth A in close up, lying before Copernicus.

My favorite crater on image 2/3 is Copernicus, a young crater from the Copernican period (somewhere between the present and 1.1 billion years ago). Copernicus is a typical Tycho-style large complex crater. It has a diameter of 93 km and a depth of 3750 meters. The crater rim rises to a height of 1100 meters above the surrounding terrain. The 54 km wide floor looks more or less flat with a group of central peaks. The walls are terraced, which you can see only vaguely on image 2/3, but if you have a closer look at the Apollo image (image 5) the broad terraces are very obvious.

A blanket of ejecta surrounds Copernicus, which is typical for a complex crater of this size. Near full Moon you can see the extensive crater ray system that surrounds Copernicus (see image 4 below, image taken with TAL 100RS). The Copernicus rays are very bright. This is caused by the fact that during the impact that formed Copernicus, pieces of bright highland material were excavated and launched into all directions. The bright material landed on top of the darker Mare lava, producing a beautiful contrast.

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Image 4 (left), Copernicus crater rays (click to enlarge), Image 5 (right), Copernicus (click to enlarge) Image credit: NASA

Copernicus is definitely my favorite complex crater. Next time I will try to get some high-resolution images of the crater itself and its immediate surroundings.
Posted by Math on 02/13 at 03:05 PM
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