The Moon sign

A Moon sign, in Sanskrit chandra rashi, is the sign the Moon occupies at birth on the sidereal zodiac. Its nakshatra, the lunar mansion, comes from the same position. The Brihat Jataka gives the Moon real weight: it calls the Moon the mind of the Kalapurusha, a zodiac drawn as a body, and devotes chapter XVI to the Moon in each nakshatra and chapter XVII to the Moon in each sign. Its own dasha scheme opens with the strongest of the Lagna, the Sun and the Moon; starting from the Moon's nakshatra belongs to the Vimshottari scheme in Iyer's note. The closing stanza of chapter XVII says its results come in full only when the Moon, the sign it holds and the ruler of that sign are all powerful.

The same book builds on the Lagna, the rising sign. The quoted sentence is from Iyer's 1885 introduction, which treats the Lagna as basic, and the houses in both the Brihat Jataka and chapter 11 of the typed Brihat Parashara Hora Shastra, edition unidentified, are counted from it. A rule that the Moon sign is the primary sign was not found in the sources read for this site. Moon-first reading is a later or regional practice that these books do not show.

The Moon travels round the zodiac in about 27 and a third days, in Clerke's 1911 figure, so it spends a little over two days in each sign and about a day in each nakshatra. The calculator finds the Moon's sidereal longitude by subtracting the Lahiri ayanamsa from the tropical one, and reads the sign, nakshatra, pada and starting dasha from that single number.