As the scientists across the country gear up to witness the longest total lunar eclipse of the 21st century - which will coincide with the closest approach of Mars to our planet - experts say that cloudy skies are likely to mar the event for amateur space enthusiasts in India.
The Astronomical Society of India cautioned against creating a hype around this event in a statement.
"For serious astronomers, this event does offer an extraordinary opportunity to study Mars through their telescopes. However, the layperson who might expect to see dramatic details of the surface of Mars would probably be disappointed," the statement said.
"Since we are in the middle of the monsoon here in India, the sky is likely to be cloudy," it said.
"People in Jammu & Kashmir, and Tamil Nadu are most likely to be able to witness the event clearly," Aniket Sule, Chair of the Public Outreach and Education Committee (POEC) of Astronomical Society of India, told PTI.
On the night of July 27, the total lunar eclipse will coincide with another relatively rare celestial phenomenon known as the Mars opposition.
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At 10:37 pm IST, Mars, Earth, and the Sun will be along as straight a line as possible.
Mars would rise around the sunset time and will set around the time of sunrise. An opposition happens when Mars is the closest to Earth in its orbit, both on the same side of the Sun.
The red planet will appears brighter and bigger than usual. Though the opposition of Mars is on July 27, it comes closest to us on 31 July. This curious fact is because the orbits of all planets around the Sun are not a perfect circle, but an ellipse.
Due to this, the closest approach of Mars to us will occur 4 days later than its opposition. This is also one of the reasons why the distance between Mars and Earth is not the same during every opposition.
The distance between Mars and the Earth ranges between about 400 million kilometers (2.7 Astronomical Units, or AU) and 56 million km (0.38AU). The closest approaches occur during oppositions.
This time, Mars comes the closest to Earth as compared to any time in the last 15 years. As a consequence, it will also appear to be the biggest and brightest in the last 15 years.
At this time, Mars will be just 58 million kilometres from the Earth.
In technical terms, the angular diameter of Mars as seen from the Earth will be more than 24" and it will be brighter than -2.75 magnitude.
For comparison, the brightest star in the night sky, Sirius will be about 3 times fainter than Mars on that day and the average angular size of the moon is 1800.
Even at closest approach, Mars will seem small. It would take a telescope equipped with a lens or mirror that is at least 6 inches in aperture to discern even the major surface features of Mars.
Nonetheless, it would be an exciting opportunity to view the bright red planet right next to the red (eclipsed) Moon on that night.
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