The sacred ten days
Inaugural Puja
Bodhon
Once the idol of Durga is brought into the pandal, the purohit (priest) instills life into the goddess (pranpratishtha) after which bodhon or the inaugural puja takes place. Bodhon generally occurs in Mahasashti or sixth day of the Hindu month of Ashwin which sets the tone of Durga Puja that formally begins from the next day,
Mahasaptami.
The puja that occurs on Mahasaptami is called Navapatrika. On the morning of Mahasaptami, a banana tree, which is considered the bride of Ganesha, is decorated. A new sari is draped around it and puja is offered to it.
On the day of Mahaashtami, the second day, the community celebrating at a certain pandal fasts and gather for a special prayer in the morning. Four rounds of puja are offered to the goddess along with flowers, belpata, tulsi as the priest chants holy mantras.
It marks sandhi or conjunction of Mahaashtami and Mahanavami (third day), according to the Bengali almanac; when the second day gives way to the third day. During Sandhi Puja, women light up 108 diyas and an elaborate aarti
This is an essential part of traditional Durga Puja celebration. On Mahaashtami or Mahanavami, an eight-year-old girl, who is considered sulakshana (bearing all the marks of a lucky child), is worshipped as Gauri or the child representative of the goddess.
On the last day of the festival, the priest does a special puja during which the goddess's image -- as portrayed in a darpan or mirror is held up to her face -- is symbolically immersed in the holy water of the Ganges kept in a container. The physical immersion of the idol takes place much later.
Once the mirror immersion is over, married women bid the goddess farewell, anointing her with sindoor (vermillion), offering sweets and paan (betel leaf). The women play among themselves with sindoor and for a moment the last hours of the festival is akin to Holi.
-- Indrani Roy Mitra