Chandrashtama: the Moon in the 8th sign from the natal Moon

Definition

Chandrashtama (chandra, Moon; ashtama, eighth) is the period when the transiting Moon is in the 8th sign counted from the natal Moon sign, counting the natal Moon sign as 1. The Moon takes about 2.5 days to cross a sign, so Chandrashtama occurs roughly once every 27.3 days and lasts about 2.5 days.

Formula

house = ((transit Moon sign − natal Moon sign) mod 12) + 1, with signs numbered 0 (Aries) to 11 (Pisces). Chandrashtama when house = 8.

Worked example

Natal Moon in Libra (6). Transit Moon in Taurus (1). (1 − 6) mod 12 = 7; 7 + 1 = 8, so this is Chandrashtama. The Chandrashtama sign for a Libra Moon is therefore Taurus.

How Jyotishya uses it

Chandrashtama is one value in the Moon-from-natal-Moon rule (Chandra gochara), which scores houses 1, 3, 6, 7, 10 and 11 as +1, houses 4 and 12 as −1, house 8 as −2, and the rest as 0. The Moon is taken at local noon each day. The score is added to the tara bala score and shown, with the arithmetic, on every day of your week.

The rule is a tradition. Jyotishya applies it without interpretation; its quick check and blind diary measure whether the scores match how your days actually go.