Skywatch Line for Friday, June 29 through Sunday, July 1, 2018

This is Dudley Observatory’s Skywatch Line for Friday, June 29 through Sunday, July 1, written by Sam Salem.

On Friday, the Sun rises at 5:20am and sets at 8:38pm; the waning gibbous Moon rises at 9:44pm and sets at 6:35am. Look westward after sunrise during the next several mornings to see the Moon in a clear blue daytime sky. The waning gibbous Moon rises after nightfall and sets in a westward direction after sunrise. This upcoming week, see the daytime Moon in the morning sky. Look for the Moon at the same time every morning to see the Moon climbing higher and higher up into the daytime sky each day all week long.

You have a good chance of spotting all 5 bright planets in one night if you can spot Mercury. The innermost planet will be the hardest to see. Mercury glows at magnitude –0.3, just above the northwest horizon and sets about 90 minutes after the Sun. Try to catch Mercury beneath Venus. Mercury is only visible at dusk and early evening. Find an unobstructed horizon in the direction of sunset. Then look for Mercury beneath Venus about 60 to 90 minutes after sunset. Use binoculars if you can’t see Mercury with the unaided eye. Venus, at magnitude –4.1, can be spotted moments before sunset fairly low in the west-northwest if you know where to look,. As twilight begins to fade, magnitude –2.3 Jupiter reaches the meridian in constellation Libra. Use a scope to examine Jupiter as soon as it pops into view. Jupiter’s multi-banded disk holds up well even when the sky is still dark blue. Saturn shines eastward at zero magnitude in northern constellation Sagittarius. This weekend is perfect for enjoying Saturn, which reached opposition on Wednesday. Saturn is up all night and reaches the meridian around 1am. Unfortunately, Saturn resides low in the south even as the planet crosses the meridian. This makes detail-rich telescopic views less frequent. Saturn’s rings are tilted toward Earth by an angle of 26 degrees. This permits easier sightings of Cassini’s Division that separates Saturn’s two brightest rings. During moments of steady seeing, the threadlike feature is visible even in a small scope. Saturn’s brightest moon, Titan, is located a few arc minutes east of Saturn’s rings this weekend.

Mars, in constellation Capricornus, shines in the southeast. Each week Mars grows a little brighter and a bit bigger. This week Mars is a magnitude –2.1 spanning an impressive 20.3 arc seconds. With steady seeing conditions, assuming a currently active dust storm doesn’t worsen, you should be able to detect some Martian surface features. Mars culminates a little before 4am, when morning twilight is noticeably brightening the sky. Mars rises in the east to southeast sky after Venus follows the Sun beneath the horizon. Seek for Mars, which is about the same brightness as Jupiter, beneath the Saturn.

Saturday mark the 45th anniversary of the longest solar eclipse in 1,000 years. In June 30, 1973, the maximum totality exceeded 7 minutes. The eclipse was observed by British, French and American scientists aboard the French prototype Concorde 001 supersonic aircraft on a flight from Las Palmas, Canaries to Fort Lamy, Chad. The path of totality crossed the Atlantic, the Sahara Desert and East Africa. The Moon’s shadow travelled at over 3,000 km per hour. Flying at 55,000 feet, the jet’s speed made possible a continuous view of the solar eclipse for 74 minutes, ten times longer than could be seen by an observer on the ground. The last total eclipse lasted over 7 minutes was on July 1, 1098. The next total eclipse exceeding seven minutes in duration will not occur until June 25, 2150.

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