Field notes · Birth chart literacy
Birth chart aspects and orbs explained
An aspect is a selected angular relationship between two points in the zodiac. LunarOtter uses conjunctions at 0°, sextiles at 60°, squares at 90°, trines at 120°, and oppositions at 180°. An orb is the allowed distance from that exact angle. The calculated relationship is geometry; its reflective meaning comes from astrological tradition.
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A worked angle example
Suppose two synthetic placements have longitudes of 10° and 132°. Their smaller separation is 122°. That is 2° from an exact 120° trine, so its trine orb is 2°. Moving a label on the wheel for readability does not alter those longitudes or the relationship.
Positions on opposite sides of zero need circular arithmetic. Placements at 359° and 1° are 2° apart, rather than 358° for aspect purposes. Our engine uses the unrounded longitudes and the smaller separation around the circle.
What the five names suggest
In astrological interpretation, a conjunction brings two themes together. An opposition highlights a polarity that may call for negotiation. A square introduces friction or a demand to adjust. A trine is often read as an easier connection, while a sextile can suggest a connection that becomes useful through participation.
These are starting points for a connected reading, rather than verdicts. A square is not a forecast of failure, and a trine is not a guarantee of success. The planets involved and the settings supplied by their houses change the question worth asking.
The exact policy used here
LunarOtter allows 8° for conjunctions and oppositions, 7° for squares and trines, and 5° for sextiles. The same orb applies to every included point. The Ascendant–Midheaven pair is excluded. A relationship outside the allowed orb does not become an aspect because the displayed values were rounded.
All accepted aspects appear in the complete paid reference table. The wheel displays twelve of the highest-ranked relationships for legibility, and the reading selects key personal relationships for interpretation. Aspects solely among Jupiter through Pluto are listed as slower shared context.
Why charts can disagree
Different software can use different aspect lists and orb allowances. One calculator might include a relationship that another excludes even when both agree on planetary longitudes. Check the aspect settings before treating the difference as a calculation error.
An approximate birth time can move a relationship into or out of its orb. Our eligibility check includes aspect membership throughout the uncertainty window. A stable Big Three alone does not prove the complete advertised reading will stay stable.
Questions people ask
What are aspects in a birth chart?
Aspects are specific angles between two planets or points, measured around the zodiac. The five major ones are the conjunction at 0 degrees, the sextile at 60, the square at 90, the trine at 120, and the opposition at 180. Astrologers read them as relationships between planetary themes, some easier and some more demanding. Two planets within a few degrees of the exact angle, called the orb, count as an aspect.
Sources and further reading
Calculation sources explain positions and coordinate conventions. Tradition sources describe astrological practice; astronomical accuracy does not validate symbolic interpretations.
- Astronomical calculation: NASA/JPL Horizons coordinate and ephemeris documentation, for positions, angles, and house geometry.
- Astrological tradition: The five major aspects, Chris Brennan and Claire Moon.
- Product conventions: LunarOtter methodology, including our uncertainty and selection policies.