Computed, written, checked.

1. The sky is computed

Every position on this site comes from the Swiss Ephemeris, the planetary engine that most professional astrology software and astro.com run on, using the DE431 data files from NASA's Jet Propulsion Laboratory. Positions are geocentric (seen from the centre of the Earth), tropical (the zodiac starts at the March equinox, each sign is thirty degrees) and apparent (corrected for the travel time of light and the nutation of the Earth's axis). That is the standard frame of Western astrology, so our numbers match a chart drawn by a professional to the arc minute.

From the raw positions the engine derives the events: each sign change by bisection to the second, each station as the zero of the planet's speed, each lunar phase as the exact angle between Moon and Sun, each eclipse from the Swiss Ephemeris eclipse functions, each exact aspect by scanning the sky hour by hour and refining every crossing. Shadow periods are found by walking the planet back and forward to the station degrees. Void-of-course periods take the Moon's last exact classical aspect in a sign to the Sun or a planet from Mercury to Pluto.

We check the result in three ways. Against an independent library, astronomy-engine, which is built on different code and agrees to within a third of an arc minute. Against published facts: the equinox of 20 March 2026 at 14:46 UTC, the three Mercury retrogrades of 2026, the annular eclipse of 17 February 2026 and the total eclipse of 12 August 2026 all come out on the minute. And against itself: the lunations in the phase table and the eclipses in the eclipse table are computed by different routines and have to agree. The dataset was last built on 2026-10-04 and covers 2025 to 2030. It is published in full on the data page.

2. The horoscope is written from the facts

Each morning at about 00:10 UTC the engine produces a fact sheet for each sign: where the Sun, Moon and every planet stand, counted as whole-sign houses from that sign; the Moon's sign changes during the day; every aspect that becomes exact that day with its time; the stations, ingresses and lunations of the day before, the day itself and the day after; and which planets are retrograde. Twelve such sheets go to a language model with one instruction: write a short reading from these facts and nothing else, in plain English, naming at least one fact the reader can check.

Then a checker reads every reading back. It parses each sentence for claims of the kind "Mercury in Scorpio", "your sixth house", "Venus retrograde", "Moon square Jupiter", and looks each one up in the fact sheet. A claim that is not there rejects the reading, and the model is asked again with the complaint attached. Readings that still fail are not published; the page then shows the facts alone and says so. The checker also enforces the house style: no dashes used as punctuation, no exclamation marks, no promises, no "the universe". The texts for the event pages (lunations, eclipses, retrogrades, planetary stays) are written and checked the same way, once.

We say this plainly because it is the point of the site. A horoscope is an interpretation; the sky it interprets should be visible and the interpretation should be honest about where it comes from. We think a reading that shows its working is worth more than one that pretends to know you.

3. Houses: two counts

The daily horoscopes use whole-sign solar houses: your Sun sign is your first house, the next sign your second, and so on. It is the convention behind every Sun-sign column and it makes the readings checkable, because "the Moon in your sixth house" then has exactly one meaning. The free chart tool uses Placidus, the most common system in Western natal astrology, which needs a birth time and place; it falls back to Porphyry inside the polar circles. If you know your rising sign, reading the daily horoscope for that sign too is the usual advice.

4. What we do not do

We do not predict events. We do not give medical, legal or financial advice, and the checker rejects readings that drift that way. We do not use your data: the chart tool runs in your browser, the daily pages set no cookies and load no trackers, and the only thing our server sees is the ordinary web request. The written Birth Chart Report, which is a paid product, needs your birth data and an e-mail address to deliver it; what happens with those is on the privacy page.

5. Known limits

The daily positions are a snapshot at 00:00 UTC; by evening the Moon has moved several degrees, which the dial on the home page accounts for by interpolation. The chart tool shows the mean lunar node, which can differ from the true node by up to a degree and a half. Historical time zones in the chart tool follow the browser's zone database, which is excellent after about 1970 and occasionally wrong before it. Eclipse visibility depends on where you stand; we give the point of greatest eclipse and the contact times, not a map. Astrology itself is a tradition, not a science, and we present its interpretations as what the tradition says.

6. Licence and reuse

The data and the horoscope texts are released under Creative Commons Attribution 4.0. Quote them, feed them to an assistant, build an app on them, with a mention of horoscope.observer. Details on the licence page.