Draconic Chart: How to Calculate It From the Node

A draconic chart is an ordinary birth chart with its zodiac turned. Western astrologers who use it start the signs not at the March equinox and not at a fixed star, but at the Moon’s north node: that point is called 0° Aries, and every other longitude is measured from it. Astronomers use the same adjective for the draconic month, the Moon’s average return to the same node. Nothing else in the chart is recomputed, so the whole calculation is one subtraction per point, and the only real decision is which node to subtract.

The Rule: Subtract the Node

For any point with ecliptic longitude L, and the north node at N:

draconic longitude = L − N, plus 360° if the result is negative

The north node itself lands on 0° Aries and the south node on 0° Libra in every draconic chart, by construction. The site’s tables use the mean node, whose tropical longitude in degrees is 125.04452 − 1934.136261 T, where T is the time from noon on 1 January 2000 (Terrestrial Time) in Julian centuries of 36,525 days. It runs backwards at about 0.053° a day. That expression was checked here against every mean-node sign change in the site’s 1950–2050 node table, and it sits on the sign edge at each one.

A Worked Chart, Step by Step

The birth is an imaginary one, 8 July 1992 at 09:20 IST in Delhi, the same example the lagna-by-hand page works through, so its ascendant agrees with that page. Positions come from the site’s own engines: the Sun and Moon from its Meeus lunar and solar series, the five planets from the routines behind the site’s kundli report.

1. The node. At that instant the mean north node is at 269°47′ tropical, which is 29°47′ Sagittarius. With the Lahiri ayanamsa of 23.75° it is 246°02′ sidereal, 6°02′ Sagittarius.
2. One point by hand. The Sun is at 106°14′ tropical. 106°14′ − 269°47′ = −163°33′, which is negative, so add 360°: 196°27′, or 16°27′ Libra.
3. A shortcut. Subtracting 269°47′ is the same as adding 360° minus it, 90°13′. In this chart every point therefore moves forward three signs and a little, and the table below shows each one doing so.

Each draconic figure is the printed tropical figure minus the printed node, and also the printed Lahiri figure minus the printed Lahiri node; the lib behind this page checks all 8 points below the node row both ways before the page is built.

Why the Ayanamsa Drops Out

A Lahiri longitude is the tropical one minus the ayanamsa a, and the node is shifted by the same a. So (L − a) − (N − a) = L − N: the ayanamsa cancels, and a draconic chart comes out the same whether it is cast from a tropical or a sidereal chart. The table shows the effect. The tropical and Lahiri columns give different signs for 7 of the 8 points (only the Moon keeps its sign), while there is a single draconic column. The ayanamsa page sets out what the Lahiri value is and which other figures it moves; in this one calculation it moves nothing. What has to match is the frame and the instant: the node and the point must come from the same zodiac and the same moment, since the node moves too.

Mean Node or True Node

Astrology software lists two different points as the north node. The mean node belongs to an averaged lunar orbit and moves smoothly; the true, or osculating, node belongs to the orbit that fits the Moon’s actual motion at one instant and swings either side of the mean one. Measured against the JPL DE421 ephemeris on the north node sign page, the two are at most 1.949° apart. Since the draconic chart is measured from the node, every draconic longitude moves by that gap when the choice changes.

In the worked chart the difference is visible in the node itself: the mean node is at 29°47′ Sagittarius, the true node at 0°38′ Capricorn, 0.85° ahead. The point nearest a draconic sign edge is the Moon, at 29°38′ Capricorn from the mean node. With the true node it reads 28°47′ Capricorn: the gap here happens to pull it back from the edge rather than over it, so no point of this chart changes draconic sign.

The site’s node table holds the DE421 true node’s sign changes but not its daily longitude, so the census below uses the true node as Jean Meeus gives it in Astronomical Algorithms: the mean node plus five periodic terms. At all 142 DE421 true-node sign changes in the table, tropical and sidereal together, that approximation sits within 0.22° of the sign edge, where the mean node alone misses by up to 1.8°; its widest swing from the mean node, 1.88°, stays inside the DE421 figure. The census sampled noon IST every 5 days from 1950 to 2050 and asked, for the Sun, Moon and five planets, whether the draconic sign changes with the choice of node:

So about one sampled instant in five gets at least one different draconic sign from the two nodes, each body taken alone between 2.9% and 3.4% of the time, and at most 4 bodies changed together at any sampled instant. Every change found lay within 1.949° of an edge, as it must. A draconic chart that does not say which node it used leaves that question open for any point close to a sign edge.

Draconic Sun Against Tropical and Lahiri Sun

Sampled at noon IST on each of 36,890 days from 1950 to 2050, with the mean node, the draconic Sun sign equals the tropical Sun sign on 8.9% of days and the Lahiri Sun sign on 8.0%. Both sit within a percentage point of 8.3%, one in twelve, the share two unrelated twelve-way labels would give. The agreement is not scattered: the draconic sign can equal the tropical one only when the node is within one sign behind 0° Aries or in Aries itself, and every agreeing day in the census has the mean node in tropical Pisces or Aries. Those days therefore come in runs, one each time the node passes through those two signs:

• 1950–1952
• 1967–1970
• 1986–1989
• 2004–2007
• 2023–2026
• 2042–2045

The 2023–2026 run is already over: the mean node left tropical Pisces this year, and no further agreeing day comes until the run beginning in 2042.

The 18.6-Year Turn of the Draconic Zodiac

Because the node runs backwards through the tropical signs, the place where draconic Aries begins slides back one sign about every eighteen months and comes round in 18.6 years. While the node is in a given tropical sign, a body’s draconic sign is its tropical sign moved back by the number of signs from Aries to that sign, or by one more (twelve back being no move at all), depending on whether the body’s degree within its sign is above or below the node’s. Over 1950–2050 every tropical sign holds the node at least 5 times, so every offset recurs. One full turn, with the mean node’s tropical sign-change dates (where a change falls so near midnight that the day is uncertain, both days are given):

The bold row is the present one: on 28 October 2026 the mean node is in tropical Aquarius, and stays there until 7 Mar 2028. The table is tropical; by the cancellation above, a Lahiri version would give the same draconic charts with different sign names for the node and different change dates. The node’s sidereal sign changes, which jyotish reads as Rahu and Ketu moving, are dated on the Rahu–Ketu transit 2026–2028 page. Re-measuring the zodiac from a different starting point is not unique to this chart: the antiscia page covers the Western practice of mirroring degrees across the solstice axis.

What This Page Does Not Give

Much of what is written about draconic charts concerns what a draconic placement is supposed to say about a person. None of that is here, for any sign, house or point: the subtraction can be checked against an ephemeris, and an interpretation cannot be checked by any arithmetic on this page. Nor are draconic houses, aspects or comparisons between two people’s draconic charts covered.

In Brief

• Rule: draconic longitude = longitude − north node, adding 360° when negative
• Zodiac: tropical and Lahiri give the identical draconic chart; the ayanamsa cancels
• Node choice: mean and true node are at most 1.949° apart, yet change some body’s draconic sign at 19.5% of sampled instants
• Sun: draconic and tropical Sun signs agree on 8.9% of days, all with the node in tropical Pisces or Aries
• Cycle: the draconic starting point turns once in 18.6 years; today it is in tropical Aquarius