How accurate are Astrollo's calculations?
Astrollo computes charts with the Swiss Ephemeris (DE431) to 0.001 degrees: ten planets, Chiron, lunar nodes, twelve house cusps and full aspects, with AI interpretation reviewed by professional astrologers.
In short
Astrollo computes your chart with the Swiss Ephemeris (DE431) to 0.001 degrees — ten planets plus Chiron and the lunar nodes, twelve house cusps (Placidus by default, with a whole-sign/equal fallback near the poles), and the full set of aspects. The astronomy is essentially exact. The interpretation is AI-drafted, reviewed by professional astrologers, and meant for reflection — not deterministic prediction.
The calculation engine: Swiss Ephemeris (DE431) at 0.001 degrees
Every Astrollo chart is built on the Swiss Ephemeris, the same astronomical engine that powers the professional software astrologers rely on. It draws on NASA/JPL's DE431 planetary data, which means positions are computed to a precision of about 0.001 degrees — far finer than the eye can read on any chart wheel.
In practice, this is as accurate as planetary positions get. The limiting factor is never our math; it's the quality of the birth details you give us (more on that below).
What we compute: planets, Chiron, nodes, house cusps and aspects
For your moment and place of birth, Astrollo calculates:
- Ten celestial bodies — Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
- Chiron — the "wounded healer" point used in modern interpretation.
- The lunar nodes — the North and South Node (the karmic axis).
- Twelve house cusps — the boundaries that map planets onto the areas of your life.
- The full aspect set — the geometric angles between points (conjunction, opposition, trine, square, sextile and more), each with its own orb.
These are the raw building blocks of your natal chart and everything that follows from it.
House systems: Placidus by default, fallback near the poles
By default Astrollo uses the Placidus house system, the most widely used method in Western astrology. Placidus divides the houses by time, which works beautifully for most birthplaces.
It has one well-known mathematical limit: at very high latitudes (close to the Arctic or Antarctic circles), Placidus cusps become unstable or undefined. When your birthplace falls in that range, Astrollo automatically switches to a whole-sign or equal-house fallback so your chart stays coherent and complete. You don't need to do anything — the system selects the appropriate method for your coordinates.
Where accuracy actually depends on you: birth time and place
The chart is only as precise as the data behind it. The astronomy is exact; your inputs set the real-world margin.
- Birth time is the most sensitive value. The Ascendant moves roughly one degree every four minutes, so a time that is off by even ten or fifteen minutes can shift your Ascendant and house cusps. If you're unsure of your exact time, enter your best estimate — you can refine it later in your profile.
- Birth place sets the coordinates and time zone (including historical daylight-saving rules). A nearby city is usually close enough; the wrong country is not.
If you can find your time on a birth certificate or hospital record, your house placements will be at their most reliable.
AI-assisted interpretation, reviewed by professional astrologers
There are two distinct layers in Astrollo, and it matters which is which:
- The calculation — fully deterministic and astronomically precise. Given the same birth data, you'll always get the same positions, cusps and aspects.
- The interpretation — the written meaning of those placements. This is drafted with AI and built on interpretation frameworks reviewed by professional astrologers, so the language stays grounded in real astrological tradition rather than invented.
The AI reads your whole chart in context — not just your Sun sign — which is why its answers reference your specific Venus, Mars, houses and nodes.
Honest note: reflection, not deterministic prediction
We want to be straight with you. The numbers are precise, but astrology is not a deterministic forecast of events. Your chart is a lens for self-reflection — a way to think about patterns, tendencies and timing — not a guarantee of what will happen. Use it for insight and perspective, and keep your own judgment in the driver's seat for important life decisions.
What next
- Browse more help articles → Help center
- Compare plans and features → Pricing
Still have a question about how we compute charts? Email us at support@astrollo.net.