Many eyes will be set on the evening sky on Saturday, the second full moon of this month, dubbed as the “blue moon” by some sky watchers.

The moon is not going to look blue, Debiprosad Duari, the director (research and academic) of MP Birla Planetarium, said. “In modern parlance, a blue moon is the second full moon in a calendar month. The time between one full moon and the next is close to the length of a calendar month. So, the only time one month can have two full moons is when the first full moon happens in the first few days of the month, in this case on October 1.”

But the original concept of a blue moon is part of folklore and practices of the medieval agrarian society, Duari said. “If a season has four full moons, the third full moon maybe called a seasonal blue moon, according to the old Maine Farmer’s Almanac.”