What is a natal chart

What a natal chart is

Looked at closely, the chart captures a single instant: the positions of the Sun, the Moon, and the planets relative to the horizon and the zodiac circle at the moment and place of birth. Each celestial body occupies a particular degree of the zodiac, and the whole chart is a set of such coordinates, tied to a date, a time, and a place.

The chart is built on astronomical data - the real positions of the celestial bodies, which can be computed to within fractions of a degree. It is not a prediction or a text "about your fate": the chart itself is coordinates. The astrological reading is a separate layer on top, based on a tradition of interpretation.

What it is made of

A natal chart is built from several elements. Here is what each one is as part of the chart, without interpreting any particular placement.

• Planets and luminaries. The Sun, the Moon, and the planets of the solar system. Astrology traditionally adds calculated points - the lunar nodes - along with bodies such as Chiron and Lilith. Each body occupies a specific degree of the zodiac.
• The twelve zodiac signs. The zodiac circle is divided into 12 equal sectors of 30 degrees each, from Aries to Pisces. The sign shows which section of the circle a planet falls in.
• The twelve houses. The houses are a division of the chart tied to the horizon and the daily rotation of the Earth at the moment of birth. They mark out the "areas of life" as a grid over the chart and depend on the exact time and place.
• Aspects. The angular distances between planets (for example, 90 or 120 degrees). An aspect is a geometric relationship between two bodies, significant when the angle is close to exact within an allowance (the orb).
• The Ascendant (ASC) and the Midheaven (MC). The two key axes of the chart. The Ascendant is the point of the zodiac rising over the eastern horizon at the moment of birth; the MC is the highest point of the chart. Both axes, like the houses, are calculated only when the birth time is known.

What data is needed and why

Calculating a chart takes three parameters: the date, the time, and the place of birth. Each one is responsible for its own part of the chart.

• The date sets the positions of the planets in the signs. The slower planets move only slightly over a day, so a date is enough for them. The exception is the Moon: it travels about 12 to 13 degrees a day and can change signs within a single day.
• The time determines the fast-changing elements - above all the Ascendant, the MC, and the houses. These points depend on the Earth's rotation and shift by roughly one degree every four minutes, so they change completely over the course of a day. The time also refines the Moon's position.
• The place is needed for two reasons: the geographic coordinates are used to calculate the houses and the axes (which depend on the latitude and longitude of the birthplace), and the local time of birth is correctly converted into a single universal time for the calculation.

This is why, without an accurate time, the chart remains incomplete: we can still compute the planets' positions in the signs, but not the houses, the Ascendant, or the MC, since those are determined entirely by the minute of birth. In that case our calculation honestly shows only what is reliably fixed and hides the houses and axes with a note to that effect. We also flag the case where the Moon changes signs during the day: without a time, its position stays ambiguous.

How we calculate it

Calculating a chart is astronomy, and here we follow a specific, verifiable method.

• Ephemerides. The positions of the Sun, the Moon, and the planets are computed by our own astronomical engine - based on well-established astronomical models (VSOP87 and ELP2000) and data from NASA/JPL. In accuracy it is on a par with the ephemerides that professional astrology programs rely on.
• Tropical zodiac. We use the tropical zodiac, in which the starting point (0 degrees of Aries) is anchored to the spring equinox. This is the standard of Western astrology.
• Placidus houses. The default house system is Placidus, the most widely used in the Western tradition. For extreme (polar) latitudes, where Placidus is mathematically unusable, we switch automatically to the equal house system (Equal).
• Five major aspects. We calculate the five main (major) aspects: the conjunction (0 degrees), the opposition (180), the trine (120), the square (90), and the sextile (60).
• Orbs. An aspect counts if the real angle departs from exact by no more than an allowed orb. The orb is not fixed: it is wider for the luminaries (the Sun and the Moon) and narrows for subtler points. When two bodies with different orbs are involved in an aspect, the stricter (narrower) of the two is used - in keeping with the classical canon.

On the limits of accuracy. The astronomical part of the calculation is precise and reproducible. But the finished chart is only as accurate as the data it starts from - above all the birth time. An error of a few minutes noticeably shifts the Ascendant, the MC, and the house boundaries, and with them the distribution of the planets across the houses. That is why we treat an accurate time more seriously than the rest of the data.

Western and other traditions

We work in the Western tropical tradition - the most widely used, and the one most readers are familiar with. It is not the only approach, and we do not present it as such.

The main difference between schools lies in the zodiac's starting point. In the tropical zodiac (our choice, Western astrology) the count is anchored to the equinox. In the sidereal zodiac, on which Vedic astrology (Jyotish) is based, the count is anchored to the actual positions of the stars. Because of the precession of the Earth's axis, the two systems now differ by about 24 degrees, so the same planet can fall in one sign in a tropical chart and in the neighboring sign in a sidereal one. There are also differences in house systems and in the set of factors used.

This does not mean one system is "right" and the other "wrong": they are different traditions with different foundations. Our charts are calculated to the Western tropical standard, and the fair comparison is with charts from that same tradition.

How to read a natal chart

This is the general principle of working through a chart, without interpreting particular placements - those belong to the chart itself, not to this page.

A chart is usually read in layers, from the general to the particular:

1. First, the pillars of the chart. You look at the Sun, the Moon, and the Ascendant: their placements by sign set the overall framework.
2. Then the planets by sign and house. For each planet, you note which sign it is in (how it expresses itself) and which house (the area in which it shows up).
3. Next, the aspects. The connections between planets show which parts of the chart reinforce, balance, or strain one another.
4. Finally, the whole picture. The separate elements are drawn together into one image, rather than read in isolation.

The specific meaning of each combination is interpretation of the chart itself, and you see it in the calculation results, not here.