Software to calculate geocentric and heliocentric planetary positions,
aspects, aspect patterns, world transits, personal transits and synastry

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April 18, 2021, 12:00 GMT
Julian date: 2,459,323.00
Ecliptic longitudes
Planet Geocentric Heliocentric
Earth 208°41'28Lib41

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VirusTotal says www.planetary-aspects.com is a totally clean siteThe programs on this website are based on exact astronomical algorithms. They are mostly described here as if they were merely astrological, but they are also useful in the areas of astro‑trading and astronomy.

There are several different types of astrology program. One difference is whether the program concerns geocentric astrology, heliocentric astrology, or both. In geocentric astrology the zodiac is viewed from the perspective of the Earth, whereas in heliocentric astrology it's from the perspective of the Sun. Most astrological software is geocentric, but astro-tradng programs often use a heliocentric zodiac. Some of our programs are purely geocentric, one is purely heliocentric, and the others support both zodiacs.

The programs below run with all versions of Windows, and on Macs with an emulator. Trial versions are freely downloadable can be made fully-functional by means of an activation key after purchase of a user license. Updates to new versions are free. For more details and to purchase a license either click on an image below or visit our Software Shop.

What's a planetary transit?

Planetary aspects occur when two planets possess a particular angular relationship with each other (e.g. conjunction, opposition, trine, square, etc.) with respect to a central point. This point is either the Earth (in geocentric astrology) or the Sun (in heliocentric astrology). A planetary transit is the period during which two planets remain continuously in a particular aspect with each other.

The programs described here either display planetary aspects and transits or calculate the exact dates and times at which transits occur (begin and end) between selected planets. Click on any of the program titles or screenshots for more information about a particular program (and the user manual). Or to get short descriptions of these programs visit our software shop.

Astrology without houses

The reason that none of these four programs involve an ascendant, or astrological houses, is that the ascendant (and thus any house system) depends on a geographical position (usually a birthplace). But aspects between planets, and thus planetary transits, depend only on the motion of the planets along the ecliptic as viewed from the Earth (or the Sun). Thus a planetary transit does not require, or imply, an ascendant (and thus no house system). Aspects and transits have their own astrological meaning. (Yes, astrology without houses is possible.) Signs (derived from the equal division of the ecliptic) are as usual, for example, Neptune is in Pisces from April 4, 2011, through March 30, 2025; and see this Su‑Me‑Sa‑Pl 4‑stellium in Capricorn on January 12, 2020). For a heliocentric example see this double kite.

There are 7 house systems commonly used by astrologers, and over 20 are possible. They give different results when interpreting a horoscope (and the Koch and Placidus systems don't even work for all latitudes). Which gives the "correct" interpretation? Or should we just conclude that the "meanings" given to houses are (arbitrary?) choices made by astrologers long ago, uncritically passed from generation to generation, and that only aspects (especially aspect patterns) and transits are important (and still to be properly interpreted)?

The developer of these computational astronomy/astrology programs (Peter Meyer) is currently available for custom software development at an affordable rate. If interested please leave a message here.