Friday, July 31, 2009

Lunar Occultation of Antares Tonight!

An interesting celestial event is within easy reach of a pair of binoculars or a small telescope, on the night of the 31st of July, from all over the country.

The occultation of Antares by Moon occurs around 9:55 P.M. in Kathmandu while 9:52 P.M. in Bhairahawa,9:54 Biratnagar,9:55 P.M. in Chandragadi,9: 53 P.M. in Janakpur, ,9:52 P.M. in Nepalganj and 9:53 P.M. in Simara.

A Lunar occultation could be the passing of the Moon in front of any other distant celestial Object - a Planet, other Solar System objects, a distant Star, or a deep sky object. Of these, the passage of the Moon in front of the naked eye Planets or bright stars, is an event that is most accessible to people without any observing equipment.And tonight is the time for the bright star occultaion by Moon.

The Star being occulted, is Jyestha or Antares - the brightest star in Scorpio. It glows with a reddish hue that gave it the name of Antares - or a rival to Mars or Aries. Moon has this tendency to repeat its occultation of a particular object in the sky, again and again, over a period of a few months. A few years back, Moon seemed to linger and linger, close to Saturn, occulting it a few times. And then, it was Venus that was getting occulted again and again. Antares, or Jyestha, went through such repeated occultations.

The website of the International Occultation Timing Association asks for accurate timings of the Antares observations towards obtaining information about the Lunar Limb profile - the contour of valleys and mountains around the limb of the visible disk of the Moon. Accurate timing of any such lunar occultation of a distant star from any one given location on Earth, would be one bite of useful data towards obtaining this Lunar Limb profile. It is just that, with brighter star occultations, the possibilities of beginning amateur astronomers with very limited equipment, also contributing to these bites of data, is increased.

A good camcorder, with a little optical zoom would be enough to record this event. A good pair of binoculars would help in being able to time the event accurately. One would need to time the event accurate to within a 10th of a second, for the data to be useful. For those wishing to just enjoy an interesting spectacle in the sky : What they would need to do is to train their eyes (or a pair of binoculars or a moderate telescope) towards the Moon in the evening – the star Antares will be viewed close to the Moon.

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