How to Read an Ephemeris

In episode 304 astrologer Patrick Watson joins the show to talk about how to use an ephemeris to study the movements of the planets in astrology. An ephemeris is a book of planetary positions that lists where the planets will be in the zodiac in the past, present, or future. In the past it was used by astrologers in order to calculate birth charts by hand, but these days it is mainly useful for studying planetary transits and cycles. During the course of the episode we give a detailed introduction to the ephemeris, talk about some of the things you can do with it, and how to use it to improve your technical skills as an astrologer. For more information about Patrick check out his website: PatrickWatsonAstrology.com This episode is available in both audio and video versions below. Ephemeris Episode Outline and Show Notes Here is an outline of some of the main points discussed in the episode: Definition: what is an ephemeris? Definition from Google/Oxford Languages: “a table or data file giving the calculated positions of a celestial object at regular intervals throughout a period.” “a book or set of such tables or files.” An ephemeris is just a listing of planetary positions. A handy way of tabulating the data. Gives you the ability to look at large compilations of data at a glance. Pronounced e·phem·er·is Ephemeris is the singular, while the plural is ephemerides. There are different types of ephemerides Astrodienst ephemeris available online for free (Swiss Ephemeris) Astro.com > All about astrology > 9000 years ephemeris Astro-Seek ephemeris: Astro-seek.com > Astro Tools > Ephemeris Tables The American Ephemeris is the printed ephemeris we use and recommend It is the most common one among US astrologers at this point. So we will focus on that and the Astrodienst ephemeris There are different varieties of the American ephemeris. Primary difference is year ranges How the main one to get at this point is the trans-century ephemeris for 1950-2050 Midnight versus noon ephemeris Midnight version starts the day at midnight Noon version starts the day at noon Difference is negligible for most planets, so either will do. I usually use the noon version so that you know where the planets are mid-day Prerequisites for using an ephemeris Memorizing the glyphs for planets and signs Memorizing the aspects ranges between planets Understanding planetary movements Ephemeris displays longitudinal movements of the planets through signs of the zodiac Along the ecliptic, which is the path of the Sun Breaking down the info shown on a page of the American Ephemeris Month, year, day All the planets and their longitudes and whether direct or retro Stations, ingresses, last aspect of Moon Moon phases and eclipses Miscellaneous astro data: asteroids, galactic center, mean node Direct versus retrograde motion American Ephemeris shades retrograde planets, which is a nice feature Seeing how fast or slow different planets move. It shows what degree and minute each planet is at at the start of the day Unless you use the noon version You have to infer based on planetary speed where it is during the day For that reason the ephemeris is pretty approximate for planets like the Moon. Astrologers used to have to calculate charts by hand based on the ephemeris Also needed an atlas for time zone changes Table of houses These days all computer programs run on a digital ephemeris Astrodienst licenses their Swiss Ephemeris for developers Astrolabe licenses the ACS Atlas licenses their atlas for developers. Book for calculating charts Simply Math: A Comprehensive Guide to Easy & Accurate Chart Calculation,  Lauran Fowks and Lynn Sellon Used to surprise me that astro programs are not real time,