The Surya Siddhanta · Chapter 7 of 8

#Conjunctions, stars and risings

#Planetary conjunctions and war (VII)

Chapter VII explains how to calculate when and where two planets will have the same longitude (VII.2–6), how to refer a planet with latitude to the ecliptic (VII.7–11), and how far apart in latitude two planets are at conjunction (VII.12–17).

Then it describes planetary war (graha yuddha), when two of the star-planets come very close:

• If their rays mingle, it is "ray-obliteration"; if less than a degree apart, a "dexter" encounter (VII.19).
• If more than a degree apart and both are bright, it is a "meeting" (samagama), not a war (VII.20, 22).
• The loser is "covered, faint, destitute of brilliancy, rough, colourless, struck down, situated to the south"; the winner is "situated to the north, having brilliancy, large — and even in the south, if powerful" (VII.20–21).
• "Venus is generally victor, whether situated to the north or to the south" (VII.23).

This is the source of the rule, used throughout Jyotisha, that a planet defeated in war is weakened.

#The stars (VIII)

Chapter VIII gives the positions of the junction stars (yogataras) of the nakshatras — the principal star of each, used to fix its place — in longitude and latitude, together with several other bright stars such as Agastya (Canopus), "at the end of Gemini and eighty degrees south", Mrigavyadha (Sirius), Agni and Brahmahridaya (VIII.1–12).

It includes a famous rule:

In Taurus, the seventeenth degree, a planet of which the latitude is a little more than two degrees south will split the wain of Rohini (VIII.13).

The "wain" (cart) of Rohini is the V-shaped group of the Hyades, with Aldebaran (Rohini) its brightest star. A planet passing through it was considered a dreadful omen — "the splitting of Rohini's cart" — which Varahamihira also describes in the Brihat Samhita.

The chapter ends by saying the stars' rising and setting are calculated like the planets' (VIII.14).

#Heliacal risings and settings (IX)

A planet near the Sun is lost in its glare, and "rises" again when it moves far enough away. The distances, in degrees of time:

The degrees of setting are, for Jupiter eleven; for Saturn fifteen; for Mars seventeen. Of Venus, the setting in the west and the rising in the east take place, by reason of her greatness, at eight degrees; the setting in the east and the rising in the west, owing to her inferior size, at ten degrees. So also Mercury makes his setting and rising at a distance from the Sun of twelve or fourteen degrees, according as he is retrograding or rapidly advancing (IX.6–8).

At distances greater than these, the planets become visible to men; at less distances they become invisible, their forms being swallowed up by the brightness of the Sun (IX.9).

These are the distances later astrologers use for combustion. The chapter also gives the distances at which the stars disappear and reappear, and says which stars never set heliacally (IX.12–18).

#The Moon's rising and its horns (X)

The Moon becomes visible in the west, or invisible in the east, at twelve degrees from the Sun (X.1). The chapter then explains how to find the time from sunset to moonset (X.2–5), the Moon's altitude and distance from the Sun at sunset (X.6–8), the illuminated part of the Moon — the Moon's elongation in minutes divided by 900 gives the bright part in twelfths of the disc (X.9) — and how to draw the crescent, showing which horn is raised (X.10–15). The tilt of the Moon's horns was itself an omen in the samhita tradition; here it is a matter of geometry.

#Summary

• Planetary conjunctions are calculated (VII.2–17); in a planetary war the northern, bright, large planet wins, and Venus usually wins (VII.19–23).
• The junction stars of the nakshatras and other bright stars (VIII); a planet with more than 2° south latitude at 17° Taurus "splits the wain of Rohini" (VIII.13).
• Heliacal setting distances: Jupiter 11°, Saturn 15°, Mars 17°, Venus 8° or 10°, Mercury 12° or 14°, Moon 12° (IX.6–9; X.1) — the combustion distances of astrology.
• The Moon's visibility, illuminated part and horns are drawn geometrically (X).

#Exercises

1. In a planetary war, which planet wins?
2. What is the "wain of Rohini", and what splits it?
3. Within how many degrees of the Sun is Saturn invisible? Mars?
4. Why does Venus have two different distances?
5. How is the Moon's illuminated part found (X.9)?

Answers: 1. The one to the north, bright and large — even in the south if powerful; Venus generally wins (VII.21–23). 2. The V of the Hyades with Aldebaran; a planet at 17° Taurus with more than 2° south latitude (VIII.13). 3. 15°; 17° (IX.6). 4. Because near inferior conjunction (retrograde) Venus is larger and brighter, visible closer to the Sun: 8°; otherwise 10° (IX.7). 5. The Moon's longitude minus the Sun's, in minutes, divided by 900 (X.9).