Sunday, October 11, 2015

Moon: Aristillos

Aaristillos Crater
James Stuby based on NASA image - Reprocessed Lunar Orbiter 4 image
Image Wikimedia
Aristillus Crater
Aristillus is a prominent lunar impact crater that lies in the eastern Mare Imbrium. Directly to the south is the smaller crater Autolycus, while to the southwest is the large Archimedes. The area of mare to the southwest is named the Sinus Lunicus. To the northeast are the craters Theaetetus and Cassini.

The rim of Aristillus has a wide, irregular outer rampart of ejecta that is relatively easy to discern against the smooth surface of the surrounding mare. The crater impact created a ray system that extends for a distance of over 600 kilometers. Due to its rays, Aristillus is mapped as part of the Copernican System.

In the northern outer ramparts of Aristillus is a ghost crater remnant. This is the protruding rim of an old crater that has been almost completely submerged by the lava flows of the surrounding Mare Imbrium. The southern end of the rim has been covered by the ejecta from Aristillus. Along the eastern inner wall and rim is an unusual narrow ribbon of dark material.

Aristyllus (fl. ca. 261 BC) was a Greek astronomer, presumably of the school of Timocharis (c.300 BC). He was among the earliest meridian-astronomy observers. Six of his stellar declinations are preserved at Almajest 7.3. All are exactly correct within his over-cautious rounding to 1/4 degree.

"Aristyllus was an early astronomer in the school of Alexandria. Little is known about him. He made astronomical observations during the first half of the third century BCE, and was probably a pupil of Timocharis.

Aristyllus and Timocharis are usually considered to have compiled the first true catalog of the fixed stars, in which stars are identified by numerical measurements of their positions."
Thomas Hockey (ed.), Biographical Encyclopedia of Astronomers. New York 2007

Aristyllus, a Greek astronomer, who appears to have lived about B.C. 233. He wrote a work on the fixed stars (τηρήσις ἀπλανῶν), which was used by Hipparchus and Ptolemy, and he is undoubtedly one of the two persons of this name who wrote commentaries on Aratus.
Sir William Smith, Dictionary of Greek and Roman Biography and Mythology. 1849

Excerpts from Wiki texts have been incorporated into the blog as kinds of abstracts for reader's convenience. By clicking the links much more can be learned about these subjects.

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