Millions of Hindu devotees were gathering on the banks of the Ganges River Sunday waiting for the stars to align and signal the best time to wash away their sins in the holy waters.

According to astrologers the sun enters the Tropic of Capricorn at 11:00 p.m., signaling the start of one of the most auspicious days of the "Ardh Kumbh Mela" or the Half Pitcher festival, a weekslong pilgrimage in the northern city of Allahabad that takes place every six years.

Nearly 70 million Hindus are expected to participate in the 45-day festival, one of the largest regular gatherings in the world, and wash themselves in the waters of the Ganges, believing it absolves their sins and ends the process of reincarnation.

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Pilgrims dip themselves in the chilly waters at the spot where the Ganges meets the Yamuna River throughout the festival but the big surge of up to five million people was expected Monday, led by the sadhus, the saffron-clad Hindu holy men, said festival organizer P.N. Mishra.

"It would be a Shahi Snan [royal bathing day] in which sadhus will bathe in the river in a big procession. Some will come riding horses, some on chariots, it will be a big show," Mishra said.

Authorities also flushed the river with fresh water from dams and canals upstream from Allahabad to try to cleanse the waters after hundreds of sadhus threatened to boycott Monday's bathing, saying the river was too polluted.

"We are trying to win them over," said R. N. Trivedi, a senior local official. "There is enough fresh and clean water in the Ganges and it is fit for bathing."

The waters have become polluted, both by the recent offerings of flowers and food cast in by the millions of pilgrims and by years of contamination as industries have dumped waste and cities pumped sewage into the river.

It was not immediately clear if the efforts of the organizers would satisfy the holy men, some who had even threatened to kill themselves in protest.

Meanwhile hundreds of thousands of pilgrims continued to flow toward the fair grounds in buses, on tractors or by foot, many carrying bundles on their heads, braving the midwinter chill to immerse themselves in the waters.

"I dip and all my sins will be washed away," said Ram Tirth, a pilgrim in his late 50s, from the neighboring state of Madhya Pradesh looking toward the Ganges where thousands of dripping Hindus shivered happily.

Security has also been tightened ahead of the big day, police said.

"We are keeping an eye on every pilgrim," said Rajiv Sabarwal, a senior police official. "Monday is a crucial day for us and we are ready to face any eventuality," he said.

According to Hindu mythology, gods and demons fought a celestial war, spilling nectar at Allahabad in a pitcher or Kumbh. A larger festival, the "Kumbh Mela," or the Pitcher Festival, takes place every 12 years.

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