Calculation and Notation

The Part of Fortune is computed from the relative positions of the Sun, the Moon and the Ascendant, using a formula that Hellenistic sources such as Vettius Valens describe as reversing direction between day and night charts, a distinction most modern calculators still preserve. It is a core technique of Hellenistic astrology described in the ancient sources, and it proved unusually durable, remaining in practical use through the medieval period and into the seventeenth century, when William Lilly discussed it under the name Fortuna in his Christian Astrology at a time when most of the other Hellenistic lots had already dropped out of Western practice. Its glyph is a cross or X set within a circle, related in form to the plain circled cross used for the planet Earth but distinguished by the diagonal, rotated placement of the cross, a distinction still followed in the astrological typefaces used by modern chart-drawing software.

The technique nearly vanished from Western practice along with the rest of the Hellenistic lot system until an organised project of translation, begun in 1993 by Robert Schmidt, Robert Hand and Robert Zoller under the name Project Hindsight, rendered Vettius Valens and other Hellenistic authors into English and restored the Part of Fortune's original calculation methods and context to a wider modern audience of astrologers.