NEW DELHI: Friday's lunar eclipse is tipped to be the longest in the century and planetariums across the country have made elaborate arrangements for enthusiasts, but rains and cloudy skies are likely to play a spoilsport in several cities.

According to Skymet Weather, residents of Delhi, Lucknow, Amritsar, Shimla, Dehradun and Chandigarh may not be able to see the rare celestial event due to a cloudy sky.

Also, those living in Kolkata, Ranchi, Karnal, Guwahati and Srinagar may remain deprived of witnessing the lunar eclipse due to bad weather.

The eclipse will also coincide with the closest approach of Mars to Earth. Earlier this year, there was a total lunar eclipse on January 31. For a total lunar eclipse of a long duration to occur, the moon has to pass through the central part of the Earth's shadow.

What will happen during the Lunar Eclipse 2018?

During this eclipse, the Moon will pass through the central part of the Earth's umbral shadow. Furthermore, the Moon will be at apogee -- farthest from the Earth in its orbit, on July 27 and will be moving at a slower speed in its orbit.

This slower moving full Moon will take longer time and greater distance of Earth's umbral shadow cone to travel, making it the longest duration of the total eclipse of this century.

How long will the lunar eclipse last?

The eclipse will last for 1 hour and 43 minutes, giving viewers a wonderful opportunity to experience the happening. It will be preceded and followed by partial eclipses lasting more than one hour.

The partial eclipse of the moon will start around 11.54 p.m. Indian Standard Time, with the total eclipse beginning at 1 a.m. on July 28.

The greatest eclipse, when moon will look the darkest, will be at around 01:52 a.m. and the totality will continue at 02:43 a.m. after this period the moon will remain partially eclipsed till 03:49 a.m. of July 28.

(With PTI inputs)