Glossary
Astrology terms
Every word in your Western, Vedic and BaZi charts, in plain words, with one thing to try on your own chart. Pick a tradition, or start with the words all three share.
House systems
House system
The rule for where each of the twelve houses starts. Different rules can put the same planet in different houses.
- What it is
- Everyone agrees there are twelve houses, but not where each one begins. Whole Sign uses the sign borders, Equal House steps 30° from the Ascendant’s degree, and Placidus divides time, which makes its houses uneven.
- Why it matters
- It is the one choice that can move a planet to another area of life with nothing in the sky changing. Two astrologers can put your Sun in the 9th or the 10th house purely by choosing differently.
- Try it
- On your Western chart, switch between Whole Sign, Placidus and Equal House. Write down which planets change house, and read both houses for each of them.
- Common mistake
- Expecting one right answer. There are dozens of systems, argued over for two thousand years, and what matters is knowing which one you are reading.
Whole-sign houses
The oldest house system: each house is exactly one sign. Simple, and the default in this app.
- What it is
- Each house is one whole sign. If Leo is rising, all of Leo is the 1st house, all of Virgo the 2nd, and so on around the chart, so the sign borders are the house borders.
- Why it matters
- It is the oldest system, used by Hellenistic astrologers from around the first century BCE, and it is standard in Vedic astrology. It also lets this app line up your Western and Vedic charts house by house.
- Try it
- Count from your rising sign to your Sun sign, calling the rising sign 1. That number is your Sun’s whole-sign house, and you can check it in "Which parts of life this lands in".
- Common mistake
- Assuming it is a shortcut for something more accurate. It is the original, used for over a thousand years before Placidus existed, and it has come back into Western use.
Placidus
The most common house system in modern Western astrology. It divides time instead of space, so its houses are uneven.
- What it is
- A quadrant system that splits the time a degree takes to travel from the horizon to the top of the sky. It is named after Placidus de Titis, a seventeenth-century monk, and spread because printed house tables used it.
- Why it matters
- It is the default in most Western astrology apps, so it is what most people have seen before. A planet can land in a different house here than under Whole Sign.
- Try it
- Switch your Western chart to Placidus and compare it with the default. If a reading elsewhere gave you a different house for a planet, this is usually why.
- Common mistake
- Believing it became standard because it was proven most accurate. It spread through printing and habit, and it breaks down at high latitudes, failing completely inside the polar circles.
Equal House
Houses of exactly 30° each, measured from your Ascendant’s degree. Simple, and it works at any latitude.
- What it is
- Take the exact degree of your Ascendant and cut twelve 30° slices from it around the chart. The Ascendant then sits exactly at the start of the 1st house, and every house is the same size.
- Why it matters
- It keeps the Ascendant’s exact degree as the starting point, which Whole Sign does not, and it avoids the stretching Placidus suffers far from the equator.
- Try it
- Switch your Western chart to Equal House. Any planet with a lower degree than your Ascendant’s degree moves back one house, so read both houses for those planets.
- Common mistake
- Confusing it with Whole Sign because both give equal houses. Whole Sign starts each house at 0° of a sign and Equal House at the Ascendant’s own degree, so with a 22° Leo rising they disagree on almost every border.
Data and time
Ephemeris
The table of where every planet was at every moment. Yours is calculated from NASA JPL data.
- What it is
- A table of planet positions over time. Astrologers used printed volumes for centuries, and this app calculates yours from NASA JPL data, the same source used to plan spacecraft paths.
- Why it matters
- It is the line between the measurable part of astrology and the interpretive part. Where the planets were is plain astronomy anyone can check, and getting it exactly right comes first.
- Try it
- Pick one planet in your chart, note its degree, and look up your birth date in any free online ephemeris. The two numbers should match to within a fraction of a degree.
- Common mistake
- Assuming astrological positions are rough or made up. They are the same numbers an astronomer would give, and astrologers disagree about meaning, never about where Saturn was.
True solar time
Clock time corrected so that noon is when the Sun was actually highest where you were born.
- What it is
- Clock time follows time zones, which are wide and set by law, plus daylight saving. True solar time corrects for the longitude you were born at and the small yearly wobble in the Sun’s motion, so noon means the Sun is at its highest.
- Why it matters
- The correction can be more than an hour near the edge of a wide time zone. That is enough to change the hour pillar in Ba Zi and move the Western Ascendant by more than half a sign.
- Try it
- Check whether daylight saving was in force on your birth date where you were born. Then make sure the time you entered in the app is the clock time from your record, unchanged.
- Common mistake
- Assuming the time on a birth certificate is astronomically exact. It is a clock reading, and turning it into a chart needs the longitude, the time zone in force that day and the daylight saving rule.