A cloudy sky was the culprit when Calcuttans missed out on the annular solar eclipse on Mahalaya. Come Monday, and a partial lunar eclipse could more than make up for the miss.

The evening after Lakshmi puja will see a partial eclipse of the moon, commencing from 5.03 pm.

A lunar eclipse occurs when the earth?s shadow falls on the moon. In case of a total lunar eclipse, the sun, earth and moon are in a straight line, while in case of a partial eclipse, they are not perfectly aligned.

?It is a coincidence that the moon rises on the Calcutta horizon around the same time on October 17,? said Debiprosad Duari, director (research & academics), MP Birla Planetarium. ?But one has to take into account the sun which sets at 5.10 pm.?

The greatest partial lunar eclipse on that day would be around 5.35 pm, when the moon is six degrees above the eastern horizon.

The eclipse would be of a magnitude of 0.06774 ? compared to 1.00 for a total lunar eclipse ? and would last till 6.02 pm.

Besides Calcutta, the Lakshmi puja spectacle can be seen from several other cities in eastern India. Those in western and central parts of the country, however, would only be able to catch the end of the eclipse.

The next instance of partial lunar eclipse, visible from Calcutta and rest of India, is September 7, 2006.

On October 3, clouds had spoilt the chance for skywatchers in the city to catch a glimpse of the annular solar eclipse. Weather permitting, all eyes would be on the lunar event, this time around.