The twelve signs do not take two hours each to rise. Some rise quickly and some slowly, and the gap grows the further you are from the equator. Brihat Jataka gives a fixed scale: 20 for Mesha, rising by 4 to 40 for Kanya and Tula, then back to 20 for Meena. It also sorts the signs by how they rise: head-first, hind-first, or both. That sorting decides which third of a dasa its results are said to show in.
☕ The sky turns evenly, the signs do not rise evenly
The sky turns once a day at a steady rate. But the zodiac is tilted against the equator. So a sign lying flat along the horizon slips up quickly, and a sign standing upright takes longer. How tilted it looks depends on your latitude.
Some rough figures, by our own arithmetic for the signs as Indian astrology counts them. Near the equator every sign takes between about 1 hour 50 minutes and 2 hours 10 minutes. At Chennai the range is about 1 hour 40 minutes to 2 hours 12 minutes. At Delhi it is about 1 hour 25 minutes to 2 hours 20 minutes. At London it runs from under an hour to nearly three hours. Everywhere the twelve add up to one turn of the sky, just under 24 hours.
Brihat Jataka gives a simple scale instead (Brihat Jataka, ch. I, v. 19). The first six signs measure 20, 24, 28, 32, 36 and 40. The next six run back down, 40 to 20. Together they add up to 360. A modern translator's note reads these as relative sizes, not the rising time at any one place.
The same book sorts the signs by the part that rises first (Brihat Jataka, ch. I, v. 10). Most of the night signs rise hind-first. The others rise head-first. Meena rises both ways. These names are used again for timing a dasa.
At a glance
- Mesha (Aries): rises hind-first · measure 20
- Vrishabha (Taurus): rises hind-first · measure 24
- Mithuna (Gemini): rises head-first · measure 28
- Kataka (Cancer): rises hind-first · measure 32
- Simha (Leo): rises head-first · measure 36
- Kanya (Virgo): rises head-first · measure 40
- Tula (Libra): rises head-first · measure 40
- Vrischika (Scorpio): rises head-first · measure 36
- Dhanu (Sagittarius): rises hind-first · measure 32
- Makara (Capricorn): rises hind-first · measure 28
- Kumbha (Aquarius): rises head-first · measure 24
- Meena (Pisces): rises both ways · measure 20
- The 20-to-40 scale is not a clock time. Real rising times depend on where you are.
- Two hours per sign is only an average. No sign takes exactly two hours.
- Meena is the only sign said to rise both ways, head and hind together.
- The dasa rule says when results are said to show. It does not say what they are.
Frequently asked questions
Which third of a dasa is said to show its results?
Brihat Jataka ties it to the sign the dasa lord is in when the dasa begins (Brihat Jataka, ch. XXII, v. 5). A head-first sign: the first third. A hind-first sign: the last third. Meena, which rises both ways: the middle third. Iyer's 1885 translation adds that the dasa is split into three equal parts.
Why do rising times change with latitude?
The zodiac is tilted against the equator. Further from the equator, that tilt makes some signs lie flatter and others stand taller as they rise. So the fast signs get faster and the slow ones slower.
Does Nava use the 20-to-40 scale?
No. Nava works out the lagna from the real sky at your birth place, from its latitude and longitude. The uneven rising times of that place are already inside the answer. Nava's dasa pages give when each dasa and bhukti begins and ends. They do not split a dasa into thirds.
Do the translations agree?
On the scale, yes. On the dasa rule there are small differences. One modern translation prints the middle group under another name, and one older one leaves Kataka out of the groups. This page follows Iyer's 1885 translation, which names all twelve.
Deep dive: from the scale to the sky
How the real time is worked out. What to read first.
🌅 How the real rising time is worked out
Astronomers call it oblique ascension: where a point of the zodiac meets the eastern horizon, measured along the equator. It needs two things, the tilt of the zodiac and your latitude.
The old siddhanta texts list it sign by sign for a given latitude. Nava does not read such a table. Its lagna is worked out from the real sky at your birth place, so the latitude is always part of it.
📚 Read first
This page builds on the twelve rashis and their classifications, where head-first and hind-first signs are introduced. For how a dasa is counted, see dasha and bhukti.