Natal Chart Calculation
Checklist
8 parts · 25 steps · Demetra George method. Work through each section from top to bottom — tick each step as you complete it.
Printable Resources
✏️Preparing Materials
Paper · pencil · eraser · ruler · compass
Ephemeris page (birth year) · Table of Houses (birth latitude) · Blank chart wheel
🕐Converting to Greenwich Mean Time
Imagine all world clocks must show the same time. Greenwich, England (UTC 0) is the universal reference.
Find timezone → check daylight saving (+1h if active) → subtract total offset from birth time
UT decimal = hours + (minutes ÷ 60) + (seconds ÷ 3600)Example: 14h 30min = 14 + 30÷60 = 14.5
⭐Calculating Sidereal Time (LST)
There are two clocks: the Sun's clock (solar time) and the stars' clock (sidereal time). The stars' clock gains ~10 seconds per hour. You need star time to place the Midheaven.
Look up 'Sidereal Time' or 'LST 0h UT' in your ephemeris for the birth date
UT decimal × 9.856 secondsThis corrects for the ~10 sec/hour the stars' clock gains over solar time
degrees × 4 + (arc-min × 4 ÷ 60) → add if East, subtract if WestEach degree of longitude = 4 minutes of time
🏔Finding the Midheaven (MC)
The MC is the highest point in the sky at your birth — the peak of the chart. It anchors house 10.
Quick estimate: LST (decimal hours) × 15 = approximate MC in degreesFor exact result: find your LST row in the table, read the MC column
IC = MC + 180°🌅Finding the Ascendant (ASC)
The Ascendant is the point rising on the Eastern horizon at birth — the gateway of the chart and the start of house 1.
Find your LST row and birth latitude column — interpolate if needed
DESC = ASC + 180°Houses 7–12 are always exactly opposite houses 1–6
| House | Cusp (° ′ Sign) | House | Cusp (° ′ Sign) | |
|---|---|---|---|---|
| 1ASC | 7DESC | |||
| 2 | 8 | |||
| 3 | 9 | |||
| 4IC | 10MC | |||
| 5 | 11 | |||
| 6 | 12 |
🪐Calculating Planetary Positions
Planets move constantly. The ephemeris shows positions at midnight (0h UT). Since you were born at a specific UT, you must interpolate to find the exact longitude at birth.
PF = UT decimal ÷ 24PF = the fraction of the day elapsed since midnight
Position = Day D + (Day D+1 − Day D) × PF⚠ The Moon moves ~12–13° per day — interpolation is especially critical here
Mark (R) if the planet is retrograde (moving backward in the ephemeris)
| Planet | Day D | Day D+1 | Final Position | (R)? |
|---|---|---|---|---|
| ☿Mercury | ||||
| ♀Venus | ||||
| ♂Mars | ||||
| ♃Jupiter | ||||
| ♄Saturn | ||||
| ♅Uranus | ||||
| ♆Neptune | ||||
| ♇Pluto |
Cross-check positions — each planet should fall neatly within one sign
📐Calculating Declinations
Declination is the celestial 'latitude' of a planet — how far North or South of the celestial equator it sits. Planets beyond 23°28′ are 'out of bounds': intensified, unconventional energy.
Use the 'Declinations' section (usually at the bottom of the ephemeris page). Same interpolation: Day D + (difference × PF). Note N or S.
| Planet | Declination (° ′) | N / S | OOB? |
|---|---|---|---|
| ☉Sun | |||
| ☽Moon | |||
| ☿Mercury | |||
| ♀Venus | |||
| ♂Mars | |||
| ♃Jupiter | |||
| ♄Saturn | |||
| ♅Uranus | |||
| ♆Neptune | |||
| ♇Pluto |
Parallel (P): two planets with nearly equal declinations (< 1° apart, same hemisphere) · Contra-parallel (cP): same value, opposite hemispheres
Any planet with declination > 23°28′ North or South is out of bounds
∠Calculating Aspects
Aspects are exact angles between planets showing how they 'speak' to each other. Allow a tolerance of a few degrees — an aspect at 118° or 122° is still a trine.
| Glyph | Name | Angle | Orb | Meaning |
|---|---|---|---|---|
| ☌ | Conjunction | 0° | ±8° | Fusion, intensity |
| ⚹ | Sextile | 60° | ±4° | Opportunity, harmony |
| □ | Square | 90° | ±6° | Tension, challenge |
| △ | Trine | 120° | ±6° | Harmony, flow |
| ☍ | Opposition | 180° | ±8° | Polarity, face-to-face |
Absolute degree = sign offset + planet degree (♈=0°, ♉=30°, ♊=60°, ♋=90°…)Difference between two planets → compare to 0°, 60°, 90°, 120°, 180°
Write each aspect with the exact orb
✦ Symbol Reference
Planets
Zodiac Signs · Starting degree for absolute position
Major Aspects