Kethiran Astrologer

KethiraAstro is a macOS desktop application that performs astronomical and astrological computations for Kethira, the fictional world of the Hârn / Venârivè setting. It plays the role a real-sky planetarium plus astrology engine would, but for that world's invented sky, calendar, planets, and zodiac.

Given a date and time on the Tuzyn calendar (TR years, 12 months of 30 days, named Nuzyael, Peonu, Kelen … Morgat) and an observer's location on the continent of Venârivè — either picked from a built-in city list (Cherafir, Berema, Lysara, Meokolis, …) or set manually as latitude/longitude — the app computes and displays:

• The position of the Sun (Nolomar) and Moon (Yael) in equatorial, ecliptic, and horizon coordinates.
• The positions of the four planets — Epeon, Alaran, Kenor, Mergus — including which sign each currently inhabits.
• The rising sign / ascendant and the elemental relationships between the planets.

Those computations are visualized as:

• A star map — a zenithal projection of the sky above the chosen location at the chosen moment, showing the constellations of Kethira's sky (Aralius, Aik, Krast, Tárael, Tylus, Lakiarn, Skôrus, Susô, Tái, Fenéri, Masâra, Ládo, Ulandus, Áhnù, Angberélius, Hîrin, Nadái …), constellation outlines (drawn after the 1990 canon revisions), the ecliptic line, zodiac-sign boundary ticks, the Sun, the planets, and the Moon drawn as a phase-correct glyph that orients its lit limb toward the Sun on the chart.
• A horoscope — a circular natal-chart-style diagram in ecliptic coordinates showing the same bodies, the constellation backdrop, and coloured "elemental lines" between the planets.
• A Sun & Moon tables view with hourly and monthly ephemeris tables and a header showing the precise time of the next full moon and next new moon (in both Ómrium Standard Time and the observer's local apparent solar time).
• A Nolomar System view listing each body's azimuth, altitude, ecliptic longitude, and current sign.
• Conjunction tables flagging planet-planet conjunctions within ±1° over daily / yearly windows.
• An eclipse table scanning future centuries for total / partial solar and lunar eclipses.
• A Venârivè map picker with a sinusoidal projection to choose an arbitrary location by clicking.

All charts and tables can be exported to SVG, PDF, or plain text. Date/time inputs and the selected location are persisted across launches.

Under the hood, the astronomy model uses canon constants from the setting's source material: a solar year of 360.0011 days, a synodic lunation of 29.999985 days, and a zodiac whose sign boundaries are pinned to Year 720 TR so that the sign-of-the-Sun function matches the rulebook. Lunar phase, syzygy, and eclipse predictions all derive from those constants, so the in-app sky stays consistent with published lore — full moons land on day 15 of each month, new moons on day 30, with the small intentional precession the world has built into its calendar.

This is based on a Java program made by Kelestia Production which I decompiled and rebuilt in Swift and SwiftUI. In addition to the interface I created for it and some additions, like the constellation outlines, I also made some corrections to the model that are listed in the following document: List of corrections.

There is also a blog post describing some of the changes I made.

The Kelestia Production product that includes the Java program, which works for both Windows and macOS and includes a 48-page PDF is located here: Astronomy of Kèthîra

Star Map - Kôlvis - 721-07-20 at 02:30 OST

The horoscope.

The location picker

The Nolomar system information

Sun & Moon tables

Conjonction tables