The pitra paksh is the period when the sun is transiting towards winter. The end of pitra paksh is the winter equinox. Subsequent to it the Matru paksh starts. It means that the forces of darkness will have an ascendence as nights begin to lengthen. That is why during this later period we invoke the various aspects of the Divine Mother, Durga, Lakshmi Kali and close it with Saraswati Puja, the goddess who ushers the spring.
These moments of transition create temporary disturbances in the vital worlds and the beings in that realm. But since they can influence our material world these pujas were occult ceremonies to quieten their disturbances. I think the linking of them to one’s own ancestors is a later religious dimension added to gain adherence to an occult tradition.
Whatever it be, the spiritual way is always higher and better than the occult and it consists of prayers and aspiration to the Divine for the good of all creatures in this world and all others. To someone who has turned to the Divine nothing else is needed than to rely upon Her Grace which is the greatest of all powers.
Affectionately
Alok da
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