What Navamsha (D9) is in plain words
Navamsha is the second most important chart in Jyotish after Rashi, the main birth chart. It needs no new observations of the sky: the same sidereal longitudes of the planets are taken, and each is converted into another sign by a division rule. “Nava” means nine, “amsha” a part: each sign of 30° is cut into nine parts of 3°20′, which makes 108 for the whole circle.
Each part has its own sign. Whichever part a planet stands in, that sign is what it gets in the Navamsha. So D9 isn't a second astronomy but arithmetic over the first. By the way, the nakshatra pada is the same cut: 27 nakshatras with four padas each give the same 108 parts, so the Moon's pada and the Moon's Navamsha are one piece of sky under two names.
The tradition reads it this way: Rashi is the circumstances of life, Navamsha is what comes of them; it is used to look at marriage, maturity, and whether the promise of the main chart will be fulfilled. This is a description of the system, not an established fact: Jyotish has no evidence base, like the rest of astrology. Only one thing can be asserted firmly — where things stand and how it was calculated.
How to calculate Navamsha: three types of signs and one formula
The classical rule is this. The parts within a sign go in zodiac order, and the start depends on the type of sign. For movable signs (Aries, Cancer, Libra, Capricorn) the first part is the sign itself. For fixed signs (Taurus, Leo, Scorpio, Aquarius) it is the ninth sign from it. For dual signs (Gemini, Virgo, Sagittarius, Pisces) the fifth. The same is put through the elements: fire signs start from Aries, earth signs from Capricorn, air signs from Libra, water signs from Cancer. The result is identical.
Behind the rule there is a simple thing. The nine parts of Aries go from Aries to Sagittarius, and the first part of Taurus is Capricorn, the next sign after Sagittarius. The chain breaks nowhere: 108 parts in a row, and over that stretch the signs go around the circle exactly nine times. So it all comes down to one formula: divide the longitude from 0° of sidereal Aries by 3°20′, take the whole part, and from it the remainder of division by 12. Zero is Aries, eleven is Pisces.
An example. A planet at 15° Taurus is 45° from the start of the circle. 45 ÷ 3.333 = 13.5; the whole part is 13, the remainder of division by 12 is one, that is, Taurus. By the classical rule the result is the same: Taurus is fixed, the ninth from it is Capricorn, 15° falls in the fifth part, and the fifth sign from Capricorn is Taurus. One more example: 5°30′ Scorpio is 215.5°; the whole part is 64, the remainder 4 — Leo. By the classical rule: start from Cancer, the second part is Leo.
Our engine uses exactly this formula, and a separate test checks the first part of all twelve signs against the classical rule. The error here is quiet: the chart is calculated without failures, it's just not the right one. The zodiac is sidereal, the Lahiri ayanamsha — and here schools differ. The Raman ayanamsha differs from Lahiri by 1.45°, and such a shift carries roughly 43% of positions into a neighboring part.
What vargottama is and how often it occurs
Vargottama is a planet whose sign in Rashi and in Navamsha coincides. It can coincide in only one part out of nine: for movable signs it is the first (from 0° to 3°20′), for fixed signs the middle one (from 13°20′ to 16°40′), for dual signs the last (from 26°40′ to 30°). Hence the probability for one planet: one ninth, about 11%.
The tradition considers such a planet strengthened, and it sounds like a rare mark. We calculated how rare. The site lays out nine points: seven planets, Rahu and Ketu. The nodes are always vargottama together: they stand opposite each other, 180° is 54 parts, and 54 gives the same shift of six signs as in Rashi. So there are eight independent points.
100,000 random moments from 1940 to 2025 were run through the engine. At least one vargottama is present in 61% of charts, none in 39%, two or more (counting the nodes as one) in 22%. If you add the lagna, at least one coincidence is present in about 65% of charts. The interpretation doesn't become false because of this, but it gets cheaper: the phrase “you have vargottama” is true for six charts out of ten and says less than it seems.
In how many minutes the Navamsha lagna changes sign
The lagna, the rising point, goes around the zodiac in about a day. There are twelve signs, so in Rashi it stays in one sign on average two hours. Navamsha has 108 parts — each takes on average about 13 minutes.
But the signs rise at different speeds, and the farther from the equator, the greater the spread. We calculated a full day with the engine. At the equator the Navamsha lagna holds a sign for roughly 12 to 14.5 minutes, at the latitude of Krasnodar from 7 to 18, at the latitude of Moscow from 4 to 20 minutes.
Now the price of an error. If the birth time is recorded with an error of 5 minutes, the Navamsha lagna ends up in a different sign in roughly 37% of cases. At 10 minutes — in 64% at Moscow's latitude and 70% at Krasnodar's, at 15 minutes — roughly 84% and 92%. A time of “around nine in the morning” from relatives' words is a lottery for the D9 lagna. Finding the time by events doesn't save you here: ours narrows a day to hours, not to minutes.
The planets are more stable. The Moon stays in one part from 5.2 to 6.8 hours, the Sun from 3.25 to 3.5 days, Mercury usually about two days, Saturn more than a month. The check is simple: recalculate the chart with the time shifted 10 minutes in both directions. If the Navamsha lagna changes, and the minute of birth is known only approximately, there is nothing to read the D9 lagna and the houses from it on.
How to test vargottama on yourself blind
The system's claim is testable: if vargottama strengthens a planet, its theme should sound louder in life than the others. The tradition describes the themes like this. Sun — visibility and authority. Moon — feelings, home, care. Mars — action and drive. Mercury — texts, negotiation, trade. Jupiter — study and mentors. Venus — relationships and pleasures. Saturn — discipline and slow work. The nodes, in one line, — a pull toward the unfamiliar and letting go.
The blind step: before the calculation, write these eight lines on paper and mark the two that sound loudest in your life. Only then open the calculation. A hit is if at least one vargottama turned out to be among the two marked. A chart without vargottama does not take part in the test. Time to the nearest hour will do, unless the vargottama is the Moon.
One chart proves nothing: two random marks give a hit in 34% of charts with vargottama, which we also calculated with the engine. That's why a threshold is needed. Collect eight charts with vargottama — your own, relatives', friends'; each marks two lines before the calculation. Chance gives on average two or three hits out of eight. Six or more it gives in roughly two series out of a hundred — that is already a signal. Five or fewer can't be told from chance, and the honest conclusion then is this: no strengthening is visible in these charts.
Deadline — a month. If eight charts weren't collected, the test did not take place, rather than “almost confirmed.” And the marks aren't changed after the calculation is opened: the whole point is that they were made in advance.
Why we show Navamsha without predictions about marriage
What is on the site. In the Jyotish section, for each of the nine points the sign in Rashi and the sign in Navamsha are shown, and the “vargottama” note is placed where they coincide. The Navamsha lagna appears if a city is given: it can't be calculated without coordinates. The same table is in the PDF reading. If there is no vargottama, it says so — with a note that this is the usual case.
What isn't there: interpretations about marriage and partners. There are three reasons. The first — interpretations of Navamsha differ between schools more than interpretations of Rashi, down to the question whether to read it as a separate chart with houses or only as a measure of planetary strength. The second — the houses of Navamsha are counted from its lagna, and that changes sign on average once every 13 minutes. A prediction about marriage would hang on a minute that usually can't be checked against documents.
The third reason is the main one. A prediction about marriage can't be checked in a reasonable time, yet it can influence a decision. A text that can't turn out to be false while it is being read, we don't hand out. The positions of the planets we do: any program with the same ayanamsha will check them, and if a sign doesn't match, the error will be found by arithmetic, not by an argument about meanings.