Agra, Oct 6 : The Taj Mahal will be open for night viewing during 'Sharad Purnima' for four nights this time. Superintending archaeologist Rajkumar Patel said, "As the Taj Mahal remains closed on Friday, tourists will be allowed to view the monument at night for four days, from Saturday to Tuesday. Tickets can be purchased one day before the night viewing date from the counter at the ASI office." Sharad Purnima will be observed on the intervening night of October 9/10. The phenomenon, called 'chamki', makes the monument's marble glow as the moonlight strikes it at different angles during this period. Tourists from around the world line up to visit the marble monument at this time. Last year, the monument was open for five nights around the full moon every month. The effect becomes even more pronounced at this time. The night viewing facility will be available for only 400 people, divided into eight slots, from 8.30 p.m. to 12.30 a.m. /IANS