Skywatch Line for Monday, October 8th and Tuesday, the 9th, 2018

This is the Skywatch Line for Monday, October 8th – Columbus Day, and Tuesday, the 9th.

The Sun sets at 6:24 PM; night falls at 7:58. Dawn begins at 5:27 AM and ends with sunrise at 7:01.

The procession of bright planets is ending. Jupiter, in Libra, is the brightest, at minus 1st magnitude. It is moderately low in the southwestern sky at 10º high. Jupiter sets at 8:04 PM.

Moving East, Saturn still resides in Sagittarius, shines with zero magnitude and is a moderate 16 arc-seconds in size. During Civil Dusk, it is moderately high at 23º, affording viewers last looks at the magnificent ring system. Saturn sets at 10:31 PM.

Mars, also still inhabits Capricornus. Now pulling away from Earth, it appears about 87% lit and shines with minus 1st magnitude. NASA reports that the dust storm continues to abate and some areas are observable. Mars is best observed at 8:36 PM and sets at 1:15 AM.

Neptune, near the star “h Aquarii”, glows with 8th magnitude and appears a tiny 2.3 arc-seconds in size. It is highest and best observed at 10:48 PM and sets at 4:24 AM. Uranus, 3º from the star Omicron Piscium, rises at 6:56 PM and is 11º high at Civil Dusk. It shines with 5th magnitude and is 3.4 arc-seconds in size. Uranus is best observed at 1:41 AM and remains up past sunrise. Both planets require detailed star charts from astronomical media.

The Moon is “New” Monday night, and rises in Virgo at 7:18 AM Tuesday, and sets at 7:07 PM.

If observing about Midnight Monday and spot meteors coming from the area of the Little Dipper (Ursa Minor), you are witnessing the Draconid meteor shower. The shower peaks Monday night. This is an irregular event, most times it is very sparse, but sometimes (1936 & 1946) thousands were observed. The Draconids, like most meteor showers, originate from debris left by comets. Comet 21/P Giacobini-Zinner is not only the progenitor of the meteor shower, it is prominent in our skies now. The meteors seem to slowly flow from the head of Draco, the constellation that wraps itself around the Pole Star. The famous Peekskill meteor that totaled a car may have originated from this shower.

Comet Giacobini-Zinner is currently at its brightest in our skies; it reaches perihelion Tuesday night. In the constellation Monoceros, near the border with Canis Major, it shines with 8th magnitude, making it easily visible in telescopes and possibly binoculars. Giacobini-Zinner is up virtually all night. Since its arrival coincides with the annual Draconid meteor shower, there is some possibility of an enhanced shower. Again, detailed charts from astronomical media assist location.

Monday is Columbus Day. Most people are familiar with the story of Columbus sailing West to reach China. When he landed in the Caribbean, he thought he had found Japan. How could he have made that mistake? Finding latitude is easy, sight on the Pole Star and measure its height above the horizon. But longitude could not be calculated without very accurate sea-borne clocks; such clocks were not invented for another 200 years. Two ancient Greeks measured the Earth. Eratosthenes accurately estimated the Earth’s diameter; Claudius Ptolemy underestimated it. Arab scholars provided other approximations of Earth’s size. They used a smaller Arabic mile, which Columbus mistook to be equal to nautical miles. Using “dead reckoning,” a navigational estimation of a ship’s course, it was natural for Columbus to mistake the island of Jamaica for Japan.

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