Methodology

Alcyona separates three layers: astronomical calculation → versioned interpretation rules → the text you read. No language model calculates positions or invents aspects. Settings below are read directly from the code that produces your chart (algorithm oj-astro-1.0.0, rules rules-2026.11-v1, methodology method-1).

Calculation

• Western tropical zodiac (measured from the true vernal equinox of date). Sidereal zodiacs are not mixed in.
• Geocentric apparent ecliptic longitudes, corrected for light-time and aberration.
• Ephemeris: Astronomy Engine 2.1.19 (MIT license), computed on our server.
• Houses: Whole Sign, only when the birth time is known. The Ascendant and Midheaven are calculated exactly from sidereal time, latitude and the true obliquity of the ecliptic; the 1st-house cusp is the start of the Ascendant’s sign and is not presented as the Ascendant degree.
• Bodies: Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. Retrograde = negative longitude speed.

Accuracy checks

Our automated tests compare 100 positions (10 bodies × 10 dates from 1905 to 2088) with NASA/JPL Horizons using the same settings (observer ephemeris, geocenter, apparent ecliptic-of-date longitude). The tolerance is 0.02° (1.2′); the largest difference measured was 53″ for the Moon and under 20″ for every other body. The Ascendant is checked to lie exactly on the eastern horizon and the Midheaven on the meridian.

Birth time and time zones

• Your local date and time are converted to UTC with the IANA time-zone database, using the rules in force on your birth date (historical daylight saving time included).
• If a time occurred twice (clocks set back) or did not exist (clocks set forward), we ask you which reading is correct instead of guessing.
• Unknown birth time: no Ascendant, Midheaven or houses. Positions are shown for local noon together with the full range covered that day. If the Moon (or another body) changed sign that day, we show both signs. Aspects that hold only for part of the day are marked “possible” and are not interpreted. For transits we only use natal bodies that moved ≤ 1.5° that day, and show dates without clock times.
• Today and Calendar use your current display time zone, which is separate from your birth time zone.

Aspects and orbs

Orbs are a methodological choice — astrologers use different values. Ours:

Natal orbs get +1° when the Sun or Moon is involved and ×0.75 for the Ascendant/Midheaven. Separation is measured cyclically, so 359° and 1° are 2° apart.

Transit timing

For each transit we scan the sky in small steps (1 hour for the Moon, 3 hours for the Sun–Mars, 12 hours for slower planets) and refine with bisection to find when it enters orb, every exact moment — a retrograde loop can produce three — and when it leaves orb. A day shows every transit whose in-orb window overlaps that local day, so contacts near midnight aren’t lost.

Choosing today’s themes

Each transit gets an editorial score = transiting-body weight × natal-point weight × aspect weight × closeness (0.5–1.0), +25% if exact that day. Themes need a score ≥ 1.5; we show up to three, at most one lunar contact, and skip outer-planet contacts to outer natal planets (shared by everyone born within years). If nothing qualifies we say it’s a quieter day.

Transit weights: Moon 1, Sun 1.6, Mercury 1.6, Venus 1.6, Mars 1.8, Jupiter 2, Saturn 2.2, Uranus 2, Neptune 2, Pluto 2. Natal weights: Sun 3, Moon 3, Ascendant 3, Midheaven 2.5, Mercury 2, Venus 2, Mars 2, Jupiter 1.4, Saturn 1.4, Uranus 1, Neptune 1, Pluto 1. Aspect weights: conjunction 1, opposition 0.9, square 0.9, trine 0.8, sextile 0.6.

Calendar themes and day labels

A transit belongs to a theme when its relevance reaches 0.4. Relevance = average of the two points’ values below, plus a house bonus when your birth time is known (3rd → Communication, 5th → Creativity, 7th/11th → Relationships, 4th/12th → Reflection & Rest).

Tone: trines and sextiles are “supportive”; squares and oppositions are “reflective” (friction that invites reflection, not “bad”); conjunctions are supportive with Venus or Jupiter, reflective with Mars, Saturn or Pluto, otherwise mixed. A day’s label for a theme compares the summed scores: supportive ≥ 2× reflective → Supportive themes; reflective ≥ 2× supportive → Reflective themes; otherwise Mixed themes; no transit → Quiet. Brief lunar contacts are listed but don’t set labels. These labels are editorial categories, not probabilities, scores of luck or predictions.

Interpretation texts

All texts are original to Alcyona and stored as versioned rules with IDs; every reading records the fact IDs, rule IDs, rules version, date and language it was built from, and the same chart + date always produces the same reading. They were written for this product and have not yet been reviewed by a professional astrologer or editor — that review is planned before commercial launch. No AI model is used to generate readings in this version.

Premium access rules

Access (access-1) is decided on our server from the subscription state confirmed by our payment provider: active subscriptions through the paid period (+48 h buffer for renewals), canceled-at-period-end through the period end, past-due for a 7-day grace while the payment is retried, and no access for unpaid, incomplete or ended subscriptions.