Analysing the Puranas, reveals that two vraths (observances) had been observed by the Andal and Gopikas during the Dhanurmasam to marry the incarnations of Lord Vishnu. One is Dhanurmasa vrath and the other is Kaathyaayani vrath.
About Dhanurmasa Vrath (a religious observance) Pooja:
A vrath done during the month of Dhanurmasam is called the Dhanurmasam Vrath. This vrath is highly auspoicious for the Vaihsnavas. This Pooja / Vrath is done during the Brahmi Muhurtha or Punya Kaal or the Maha Punya Kaal which is the period of one and a half hour before the start of sun rise, i.e., between 04.00 am – 05.30 am.
Andal had performed this wrath for the first time to marry Lord Vishnu.
How to perform Dhanurmasa Vratha?
Lord Brahma had personally explained about the Dhanurmasa Vratha to Sage Maha Muni Naradha. It has been prologued in the Brahmanda, Bhagawatha and Adhithya Puranas.
1) Wake up little bit early to the Brahmi Muhurtha time (03.30 am). Take a bath and prepare Jaggery Pongal / Havishyanna / Mudhganna or a normal pongal.
2) Offer Thulasi Leaves (Basil), some flowers, HOT Pongal to Lord Vishnu (for the first fifteen days). First worship Lord Ganesha. Then worship Lord Vishnu. Before the pongal get’s cool, finish a simple prayer and donate some pongal to a Brahmin. If a Brahmin is not available then finish the prayer starting with the Ashtothara Namas of Lord Vishnu and Goddess Sree Lakshmi for those who need prosperity. Serving the pongal hot give good fruits for your life.
3) The next fifteen days of the pooja should be offered with Dhaddhojanam (boiled rice mixed with curd, ginger, grapes, even can add green grams).
4) Pray the other Gods who are responsible and grants the other Dharmas mentioned in the Hindu Shasthras. Recite the Vishnu Purana and other slokas related to other gods.
Giving the Pongal to a Brahman for all the 30 days of the month benefits with the required Prosperity, Good Health, and Moksha (heaven) for life.
If the Puja is finished when the stars are still twinkling on the skies, then it is said to be the highest quality of worship that accomplishes the desires. Puja that is finished after the stars are vanished and before sunrise are said to be medium rated. Whereas puja that is done or finished after sunrise is said to be inferior with no bestows from the Gods. Puja performed in the afternoon is also said to be useless.
In this month, one should wake up early in the morning and go to bed as soon as possible.