Pitra is referred to our ancestors and family members who are dead. Pitra Dosh is referred to the situation when the departed ancestors or family members have not attained peace or salvation. Importance of blessings from Pitra is explained in Rig Veda (Book 10: Hymn 15). This hymn contains a set of 14 verses and these verses outlines the importance of pleasing Pitra along with the basic procedure to please them and benefits of pleasing the Pitra.
आच्या जानु दक्षिणतो निषद्येमं यज्ञमभि गर्णीतविश्वे | मा हिंसिष्ट पितरः केन चिन नो यद व आगःपुरुषता कराम ||
Our ancient fathers who deserve the Soma (Nectar) who came, most noble, to our banquet. With these let Yama (God of Death), yearning with the yearning, rejoicing eat our offerings at his pleasure.
Astrologically Pitra Dosh is usually seen by Sun - Rahu conjunction or Rahu aspecting Sun in the natal horoscope. The result of Pitra Dosh will largely depend on the house in which Sun and Rahu are conjunct. Moon and Rahu conjunction may also lead to Pitra Dosh, which at times is referred as Maitri Dosh. Some astrologers take Maitri Dosh to be arising on Mother's side and Pitra Dosh on the Father's side. There are some other combination of planets in the birth horoscope which may lead to Pitra Dosh too. An expert astrologer is the best judge to decide over the extent and the effect of Pitra Dosha.
Pitra Dosh Nivaran Puja helps in overcoming the negative impacts of Pitra Dosh. This Puja is often performed at a few designated places like Gaya, Banaras, Pehowa, Tryambkeshwar, Hardwar etc. Gaya is believed to be the best place for Pind Daan and it is believed that many mythological figures like Lord Rama, Yudhistra, Bhisma Pitamaha, Marichi (Brahma’s son) performed Pind Daan at Gaya. Some people choose to perform this Puja at home too. An expert astrologer or a senior Pandit should be consulted when performing this Puja at home.