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Lunar Occultation of Antares

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, for many parts of the country.

A large part of India, in a belt passing just south of Delhi, spanning the entire country, and ending in the Indian Ocean (as can be seen from the image below, from, can view this interesting celestial event.

This event will be the Lunar Occultation of Antares, taking place on the evening of the 31st of July 2009.

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. In 2007 there was an interesting Lunar Occultation of Venus and an Occultation of Mars happened in 2008, events that were visible from Delhi and many parts of India. In recent times, there has not been any bright star occultation by the Moon, seen from India. Now it is the time for a bright star occultation, again.

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.

The belt through which this event can be seen, crosses just a little to the south of Delhi, within easy reach from the suburbs of Delhi.

What will be seen from Delhi, will be an intriguingly close conjunction between the Moon and Antares, with the relative positioning between the two changing with time. Although the occultation itself will not be seen from Delhi, this close conjunction with its changing relative position so clearly visible, in itself, would be interesting to observe.

A team of observers from the Science Popularisation Association of Communicators and Educators (S.P.A.C.E.), Nehru Planetarium and the Amateur Astronomers Association, Delhi, will be going to a site in Nuh, Haryana, from where the event will be seen as a graze occultation, when the star Antares will be seen to just momentarily disappear behind the Moon and reappear immediately.

Such graze occultations are very useful when timed accurately, to give information about the contour of valleys and mountains on the Moon the Lunar Limb Profile. Interestingly the topography of the Moon is not as well known as that of Mars, which has had several orbiter missions mapping its topography thoroughly. Of course, once the data from the terrain mapping camera of the Chandrayaan, maps the lunar terrain thoroughly, it will no longer be possible to obtain new information about lunar topology from lunar occultation observations by amateur astronomers. So, hurry up and collect this data, before it becomes not so useful to observe lunar occultations, soon.

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. As seen from Bhopal, Around 9:12 PM it will be seen to slip behind the Moon and reappear from the other end at around 10:11 PM. From location to location, the timings will change. The graze from Nuh, will be observed at about 9:38 PM.

Agra9:28 PM10:56 PM
Allahabad9:28 PM10:19 PM
Bangalore8:57 PM10:35 PM
Bhopal9:12 PM10:12 PM
Hyderabad9:04 PM10:31 PM
Indore9:06 PM10:09 PM
Jabalpur9:18 PM10:20 PM
Jaipur9:13 PM9:37 PM
Kanpur9:28 PM10:09 PM
Kochi8:51 PM10:35 PM
Kolkata9:35 PM10:46 PM
Lucknow9:31 PM10:09 PM
Mumbai8:48 PM10:10 PM
Varanasi9:30 PM10:23 PM

Useful general urls for understanding the significance of Lunar occultations as tools to study celestial objects

Some serious science connections with lunar occultation studies

  • Estimation of angular size of radio sources through Lunar Occultation Radio studies

  • Angular size of Antares estimated through Lunar Occultation observations

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Page last modified on July 30, 2009, at 12:41 PM EST