Tropical zodiac
Western astrology birth chart explained
A Western natal chart maps the tropical positions of the planets at a specific date, time and location, then organizes them through signs, houses, angles and aspects.
What a Western birth chart calculates
The calculation begins with planetary longitudes in the tropical zodiac. Exact birth time and location are then used to calculate the Ascendant, Midheaven and house cusps.
Angular distance between planets is compared with recognized aspect angles such as conjunctions, sextiles, squares, trines and oppositions.
Why birth time matters
The Moon can move noticeably during one day, while the Ascendant and houses change much faster. A recorded birth time improves the reliability of houses, angles and timing comparisons.
Interpretation with evidence
ReadAstrology keeps placements and aspect measurements separate from the interpretive narrative so you can inspect the sign, house, degree, aspect and orb behind a claim.
Frequently asked questions
Does Western astrology use the tropical zodiac?
Yes. The Western chart in ReadAstrology uses tropical zodiac positions.
What is an orb in astrology?
An orb is the difference between the measured angular separation of two chart points and the exact angle of an aspect.
Can I calculate a chart without a birth time?
Some planetary placements can still be calculated, but the Ascendant, houses and certain timing details may be unavailable or less reliable.