Dasa

The chart shows where the grahas stood at one moment; it does not say when in a life each of them will make itself felt. Jyotish answers that with dasas (periods): a dasa system cuts a life into a sequence of periods and hands each one to a ruler, a graha (planet) or a rasi (sign). While a period runs, its ruler's promise in the chart is the one coming due. Timing of this kind is one of the things that set Jyotish apart, and the tradition knows hundreds of such systems.

Periods within periods

Each period divides again by the same system's rules. The top-level periods are the mahadasas, "great periods"; each mahadasa splits into antardasas, and each antardasa into pratyantardasas. The splitting can go further still, down to spans of days, but these three levels are the ones most often named. A moment in a life thus sits in one period at every level at once, and a reading weighs the rulers of all of them together: the mahadasa sets the background, the shorter periods inside it the foreground.

What a system starts from

Systems differ first in what they count from:

• A nakshatra dasa starts from the nakshatra (constellation) the Moon is in. The order of the periods follows from where the Moon was at birth. Its periods mostly belong to grahas, though the Kalachakra dasa gives them to rasis.
• A rasi dasa starts from the rasis and the grahas standing in them, and its periods belong to rasis rather than to grahas.

What a system is for

Systems differ also in the question they answer. An ayur dasa (a dasa of longevity) is read for the length of life and the dangers to it; a phalita dasa (a dasa of results) for the events and fortunes of a life in general. Some phalita dasas narrow further, to a single field of life.

Many systems, one life

With so many systems, it is tempting to think of them as competitors, each claiming to time the same events, of which only one can be right. That is not how they are meant to be used. Each system looks at one side of a life: when two of them say different things about the same years, they are usually talking about different matters, and both can hold. A system built for longevity says little about career, and one built for wealth little about health. The skill lies in asking each system only the question it was made for.

Ahead in the book

The book teaches nine natal dasa systems in Part 2, chapters 16 to 24, and the Sudarsana Chakra dasa in chapter 31. The nakshatra dasas among them are the Vimsottari (chapter 16), the Ashtottari (17) and the Kalachakra (24); the rest are rasi dasas, from the Narayana dasa (18), read for life in general, to the Shoola dasa (23), read for longevity. The Vimsottari dasa comes first: it is the most widely used, and the one whose rulers the chart page already names.

hora does not calculate dasas yet; as it learns them, chapter by chapter, they will get pages of their own.

In the chart

The chart page's table has a column of Vimsottari lords: for each graha and the lagna (ascendant), the graha that rules the nakshatra it stands in, in the Vimsottari dasa. The column's heading links to this page. The lord of the Moon's nakshatra matters most, since the Vimsottari dasa counts from the Moon; how it does so is the subject of chapter 16.

Book reference: P.V.R. Narasimha Rao, Vedic Astrology: An Integrated Approach, chapter 1, § 1.4. Where to get the book