Magha Shraddha is performed inPitri Paksha when Magha Nakshatra prevails during Aparahna Kala (Post Meridian).
If Magha Nakshatra prevails partially during Aparahna Kala (Post Meridian) on two days then the day
when it prevails for longer duration is considered suitable for performing the rituals.
If both Magha Nakshatra and Trayodashi Tithi prevail during Aparahna on the same day then it is known as Magha Trayodashi Shraddha .
It is generally the 13th day of Mahalaya or Pitri Paksha.
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Nakshatra Magha is significant in Pitri Paksha because it is ruled by Pitris(पितृ),
translates to fathers but also used for forefathers and great forefathers, the spirits of the departed ancestors.
Pitri Paksha or Mahalaya Shraddhas are Parvan Shraddhas(पार्वणश्राद्ध) and auspicious time to perform them is Kutup Muhurt and Rohina Muhurt.
It could be performed till Aparahna Kala (Post Meridian) gets over.
Tarpan (तर्पण) could be performed at the end of the Shraddha.
Tarpana is performed with Til, water and other materials by offering to ancestors. Tarpana could be performed on any day but on Shraddha these are usually performed at the end.
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