Book Reviews

The American Ephemeris

Neil F. Michelsen (Programming) & Rique Pottenger (Revisions)


Essential for Students to Professionals


Data! Numbers! Glyphs!

Let’s begin by taking a moment to contemplate and appreciate the magnitude of effort and tech wizardry Neil Michelsen must have put into compiling the very first edition of this book of planetary phenomena in the late 70’s. Readers, this man is a genuine godsend to the astrological community, founding Astro Computing Services (ACS) in 1972 to provide astrologers access to accurate and affordable astrology charts. Imagine not being able to type your birth info into a computer or device and immediately have a detailed chart in your hands in less than a blink? Well this was once a thing, and not so long ago. Neil Michelsen was not a practicing astrologer, but was an astro enthusiast who had a brilliant way with computers and astronomical data. He also put all profits made from ACS back into the astrological community. Who even does that these days? What a guy, what an amazing human. 

So what on Earth is an ephemeris I hear you ask, besides a phenomenal book full of phenomena? Hey Google!

Ephemerisnoun – a table or data file giving the calculated positions of a celestial object at regular intervals throughout a period

Oxford Dictionary Online

Coolios, sounds bland, no? Dictionaries tend to do that. But it’s what lies inside The American Ephemeris that will blow your mind. Phenomena! Data! Data about phenomena! As in- accurate daily calculations of the movement of the planets through the signs – Sun, Moon at midnight and midday, True Nodes, Mercury, Venus, Mars, Jupiter, Uranus, Neptune, Pluto. Accurate information on planetary ingresses, void of course and stations, declination (for you Out of Bounds enthusiasts), Lunar Phases & Eclipses, Julian days, Delta T, SVP, Obliquity, the position of planetoid Chiron, the Mean Lunar Node. So many mysterious things. Want to know what they all mean? Get yourself an American Ephemeris. It is truly phenomenal. Sorry, I couldn’t resist.

Now for a little astro tea…

…in April 2019 an article was published online about the rise in popularity of astrology amongst Gen Z. Many highly esteemed, well-regarded astrologers with extensive years of study and practice under their belt were interviewed and it was pretty terrific. No dissing astrology, no skeptic weigh-ins, just a fun, well-researched and well-written article. The first astrologer mentioned was so successful she had recently resigned as an editorial assistant at a high end magazine to do astrology readings full-time, pulling in over $4k a month through a large and loyal fanbase on social media. Kudos and bravos all round!

But wait. There’s more. As with all hot topic articles, the Uranian kick in the ass moment lay in wait at the end. Our super successful astrologer, the one making the big bucks…was getting all of her astro information online. Information available to anyone with a smart device and an internet connection. She did not actually own an ephemeris, let alone know how to use one. Oof. And WTF? There goes every astrologer’s hard won credibility. WTAF.

An understandable chorus of disbelief and dismay erupted in the international astro community. There were heated debates on social media over whether an astrologer even needed to know how to use an ephemeris in this digital world (Yes. Yes you do). Astrologers who have studied extensively, and often at great cost, were feeling all the Mars feels. Rightfully so imo.

Here’s why. Learning to use an ephemeris is first year astro class stuff. You take the class. A little while in, you buy the book. You open it up. There are soooo many number and columns and the paper is so thin and the book is so thick. You freak out. This, this! is the moment where your interest and curiousity in astrology diverges into “Uh, lol, no thanks” or “This is my chosen path and I will conquer it and become an Astrologer”, with a capital ‘A’, and some superhero music to accompany the revelation. It’s a great moment if you choose to accept it. You will get to know every single part of this book, eventually. Neil Michelsen would be proud.

Allow me a moment on my soapbox.

If you do not own and use an ephemeris for your astrological work, you are not an Astrologer with a capital ‘A’, and you should not be charging people for information you’ve gleaned off the web. You’ve gotta start at the beginning and learn the basics first (and sucking at high school maths is no excuse) if astrology is your chosen career. The astrological community struggles hard enough to gain credibility for our years of study and work as it is, without being undermined from within. This is a hill I will die on and happily. NFG. Check out the article here if you are keen –

Rant over. This is just my opinion ofc. But do you really want to be held in the same regard as people who don’t really understand much more than how to market their Google searches? Think of Neil Michelsen working away on bulky computers accumulating all this data for us. Now imagine telling him people raking in the big money from astrology don’t actually use this information. Sigh. And wearily stepping off my soapbox now.

Ah yes, book reviews. The reason we are here. The 21st Century edition has been revised and updated. There’s an adjustment from Universal Time to using Ephemeris Time, the Delta T values have been removed, but the position of the Galactic Centre has been added. It makes sense to incorporate data for the many different streams of astrology now in use, and the reasoning behind these changes is explained clearly in the first few pages. Seriously, there is a wealth of astro information between the covers of these books. Best of all, and I guarantee this, you will feel ten times smarter after reading just the inside cover. Phenomenal, huh!?!

There are a range of versions currently available at the usuals – Book Depository and Amazon, though I notice the 20th Century 1900 – 2000 versions are getting exxy. Due to the sheer amount of data in these books, none of them are available on Kindle. If you are ever in desperate need of an online ephemeris check out Swiss Ephemeris –

Happy astro reading!


Phenomena, data, real juicy know your stuff astrologer data


ACS Publications

San Diego, California

1980 – still in print with multiple versions

Reviewed copies 

  • 20th Century (Red Cover) – 1995
  • 21st Century (Blue Cover) – 2002

Biographical info from-,_Neil