This is Dudley Observatory’s Skywatch Line for Friday, June 20, through Sunday, June 22, written by Alan French. Reaching last quarter on Thursday, a waning crescent Moon will rise well after midnight, leaving the evening skies nice and dark. Saturn was once thought to be unique – the only planet with rings. It remains the only planet with rings visible through amateur telescopes, but Jupiter, Uranus, and Neptune also have rings, although they are very faint. Astronomers have recently discovered that asteroid Chariklo has two dense, narrow rings. Chariklo is the largest confirmed asteroid in the outer solar system. Its orbit lies between Saturn and Uranus and it is 250km in diameter. Galileo was the first to observe Saturn with a telescope, but he thought the rings were two moons, one on either side of the planet. In 1655 Christen Huygens, who had observed the planet with a telescope magnifying 50 times, suggested that Saturn was surrounded by a solid ring. It was another 200 years before James Clerk Maxwell correctly deduced that the rings were composed of many small particles orbiting Saturn. We now know the ring system is very complex and have gotten superb views of its fine detail from the Cassini spacecraft. The ringed planet is now due south and highest just before 10 pm, when it will be 32 degrees above the horizon. This is the best time to catch a view of Saturn’s gorgeous rings, which are visible in any modest telescope magnifying about 30 times. A magnification of 60x, the maximum for many birding scopes, provides a better view. Saturn will be a feature target at June public star parties held by the Albany Area Amateur Astronomers. Weather permitting, the Albany Area Amateur Astronomers, in association with New York State Parks, will hold a public star party in Grafton Lakes State Park beginning at 9:00 pm on Friday, June 20. If you arrive after dark, please use the winter entrance. For further information call Ray (658-3138) or Bernard (658-9144). If the skies are cloudy on Friday, the star party will be held on Saturday night, if the skies are clear. Call if in doubt. Next weekend, June 27 and 28, there will be public star parties at Landis Arboretum. There will also be a talk and star party at the Octagonal Barn in Delanson on Friday, June 27. Look for details in next weekend’s Skywatch Line.
Posted on: Thu, 19 Jun 2014 20:44:28 +0000
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