अष्टका

In short AShTakA is a shrAddham mandated by apastamba as well as other sutrakaras. For Apastambins its has to be done on Maagha Krishna Ashtami, every year.

The previous day (purvedyu) after saayam aupasanam the karta has to make a purodasha like adai or using ashta kapala on the aupasana agni. Then there is homa of the purodasha, after which the 8 bhoktas of aShTakA shrAddham have to be given dinner when the balance purodasha to be served to them.

On the aShTakA day, varaṇam, kr̥sara+++(??)+++, snānam, pādyam etc to be done like normal shrAddham, then homa - 22 ahutis. Then brāhmaṁa bhojanam, piṇḍa pradānam. The sutra says that go-māṁsa and vapā-homa has to be done. But we substitute asamskr̥ta-ājya for these homas, using a separate asamskr̥ta-darvi.

The following day is anvaShTakA - it is just like a normal paravana shrAddham but varanam, homa, bhojana and pinda pradana has to be done for mātāmaha-varga also. purUrava-Ardrava are the vishvedevas for both aShTakA and anvaShTakA. Also, shraddhanga tarpanam is done before the shrAddham like in darsha shrAddham on both days.

The sutra also says the go maamsa from the AShTakA shrAddham has to be kept overnight and served on anvaShTakA too. We just do this with remnant aajya. Apastamba has given an alternate gauna prayoga too called dadhyanjali homa on aShTakA day. This does not require purvedyu aupakArya, but anvaShTakA has to be done.