Luís Ribeiro's Fascinating Astrolabe

In a podcast of 31 July 2021 (Episode 313 of The Astrology Podcast), our colleagues Luís Ribeiro and Chris Brennan met in order to explain the mathematical and/or astronomical basis of the different systems of house division to the astrological community, from whole-sign houses and the houses of Porphyry to the Alcabitius and Placidus measurements of time. After concluding a masterful presentation of each, Luís bothered to employ an ancient instrument, an astrolabe designed for the city of Lisbon (Portugal), in order to measure the cusps of houses according to Alcabitius. Without Chris and Luís realising it, perhaps, the plate of the astrolabe seems to have been designed under the rigours of primary motion, that is, under a Placidian conception, so that, by conducting the exercise or by rotating the rete of the astrolabe in order to establish or make out the cusps of Alcabitian houses, Ribeiro corroborates or confirms both the natural integrity and the theoretical strength of “the method of rising times” (Abraham Ibn Ezra, 12th century) or “the astrolabe method” (Robert Powell, 1996). Although we have before explained the Placidian mechanism of action and even established and demonstrated a close relationship between Placidian house cusps (i.e. seasonal times) and relativity from the standpoint not of the two forms of relativity known to man since Albert Einstein, special and general, but from that of the equation of time (i.e. basis of tropical astrology), we yet again take care to explain it, this time under the light of this fascinating astrolabe presented by Luís Ribeiro.