Partial lunar eclipse (File Photo)
The July 16 lunar eclipse, which will be the last of its kind in 2019, is a special coincidence as it will be occurring with Guru Purnima after 149 long years. Guru Purnima, a spiritual tradition in Indian religion, is celebrated to honour the teachers and leaders of our life and every year falls on a full moon day (Purnima) in the Hindu month of Ashadha (June–July). The festival was revived by Mahatma Gandhi to tribute to his spiritual guru Shrimad Rajchandra.
On January 21, 2019, sky gazers witnessed the first and only total lunar eclipse of the year, with the next one scheduled to take place on May 26, 2021. Before 2021, there will be penumbral eclipses at times, though these are not total or partial lunar eclipses.
For those waiting eagerly to witness the rare natural phenomenon on July 16-17 night, the three-hour-long eclipse will begin around 1.31 am on Wednesday and will be at its pick around 3 am. The Moon will remain partially eclipsed till 4:29 am, leaving a golden opportunity for the sky gazers to watch the greatest partial eclipse almost throughout the night. Apart from India, the celestial phenomenon will be visible in parts of South America, Europe, Africa, Asia and Australia.
Partial lunar eclipse takes place only at full Moon night, when the Moon, the Sun and the Earth are in a perfect straight line. As the Sun's rays fall on the Earth, its shadow falls on to a patch of space. When the Moon enters the patch of shadow there is lunar eclipse. The patch of shadow is actually composed of two cone-shaped parts - one nestled inside the other.
The outer shadow or penumbra is a zone where the Earth shadow is partial and blocks some, but not all of the Sun's rays. In contrast, the inner shadow or umbra is a region where the Earth blocks all direct sunlight from reaching the Moon. When only a part of the Moon passes through the umbra, a partial lunar eclipse is seen. If the entire Moon passes through the umbral shadow, then a total eclipse of the Moon occurs.
The Moon's average orbital speed is about 1.03 km/s (2,300 mph), or a little more than its diameter per hour, so totality may last up to nearly 107 minutes. Nevertheless, the total time between the first and the last contacts of the Moon's limb with Earth's shadow is much longer and could last up to four hours.
Going by the experts' advice, lunar eclipses are completely safe to view with the naked eye and one does not need a telescope to watch the phenomenon. However, a good pair of binoculars are advised by some astronauts for a better experience.