The Western Sidereal Astrology Interpretation Workbook by Kenneth Bowser, Sidus Press, 2020. Large Format (8.5 x 11) Softcover, 426 pages, $300.


By Mary Plumb


Kenneth Bowser has practiced sidereal astrology for more than 50 years. This book, which is essentially a guided course, begins with the author’s masterful explanation of the components (summarized in the excellent Rules of Interpretation and Glossary of Terms), which include the added dimension of aspects for the equatorial system, that is, mundane (or in mundo aspects, also known as parans); fixed stars; and the more familiar aspects used in the ecliptic system. Mundane aspects are tied to the Earth’s rotation on its axis and are measured using Right Ascension and Declination. Coordinates along the ecliptic are measured in celestial latitude and celestial longitude and are derived from the Earth’s revolution around the Sun. Bowser gives ample evidence to support the statement, “If you ignore the equator for the ecliptic, you ignore half the horoscope.” This work can be studied by both tropical or sidereal astrologers, since the same rules of interpretation apply.

After the introductory material, the Workbook begins. In Part One, there are 25 unnamed horoscopes with questions and prompts to guide the reader to interpret the chart (and lots of space to write). In Part Two, Bowser names the individuals and gives meticulous analyses of each chart. His interpretation are extensive—two to five thousand words each. When the reader/student, going at his or her own pace, completes Chart #25, Bowser will critique the work and give a two-hour tutoring session. This is a wonderful format for learning from a superb astrologer. If Ken Bowser’s work is new to you, go to the website to read an extensive interview (originally published in TMA in 2004) to appreciate the depth of his astrological knowledge.

By Victor Olliver


The main focus of this review is on Western Sidereal Astrology Interpretation Workbook, the basis of a study course in western sidereal astrology run by the celebrated astrologer Kenneth Bowser. I would advise that you first acquaint yourself with his first book An Introduction to Western Sidereal Astrology (Third Edition) before turning to the Workbook, which shows how to apply sidereal knowledge to the art of chart interpretation. The Workbook is actually a course book with many practical exercises.

Most practitioners understand the basic difference between tropical and sidereal systems. While the tropical zodiac starts at the Vernal Equinox point in the Northern Hemisphere, the sidereal defines zodiac signs against the apparent backward movement of fixed stars —the precession of the equinoxes—at a pace of about 1 degree per 72 years. Western sidereal astrology applies the same rules of interpretation (with a few minor differences) as those practiced in the tropical, so tropical and sidereal astrologers won’t struggle with this branch of sidereal. 


Kenneth Bowser wrote me: ‘It’s a new course. It’s designed to open up the equatorial system to general use. Most people don’t stray from the ecliptic system except to mention parallels, but they very rarely address Right Ascension. The only time it’s mentioned generally is in setting up the chart, but almost nobody does that by hand anymore, which keeps people estranged from sidereal time, even though as the hour angle of the Vernal Equinox, it’s a tropical parameter. The examples in the book are in terms of the sidereal zodiac because that’s the mode I favor.’ Western sidereal was revived by the 20th century astrologer Cyril Fagan. As Bowser writes: ‘Interest in western sidereal has steadily grown since Fagan’s death in 1970.’

The Workbook course has two sections. In Section One, there are 25 charts with no names or data. Each chart is accompanied by nine questions/prompts that help you to identify the dominant themes in each horoscope. After you’ve answered the questions and written your interpretation, you turn to the corresponding chart in Section Two. There you will find the chart with the name, data and interpretation. These detailed interpretations run between 2000 and 5000 words each. The Workbook includes a page to note what you’ve learned and what you may have missed in your own interpretation. In this way, you hone your skills and expand ability to correctly read astrological symbolism. The course also includes two hours of private tutoring.

Western sidereal looks at aspects in two coordinate systems, equatorial and ecliptic, to discover hidden mundane aspects that help enlarge interpretation. This system also uses fixed stars. The Workbook itself is a spacious tool with succinct guidance notes and beautifully laid out charts. The perfect accompaniment if you fancy a fascinating and accessible adventure in astrology.


By Armand Diaz

I might as well say it: I’m no siderealist. I’ve had a few prickly conversations with people who smugly announce that the sidereal zodiac is the ‘true’ zodiac and that those of us who use the tropical system are mistaken. Ken Bowser is different. A luminary in the world of Western sidereal astrology, he certainly argues strongly for the use of the sidereal zodiac, and makes a good case for it. Yet as much of a siderealist as he is, he’s not dogmatic. Rather than barking about the true zodiac, he invites us to look at the evidence and consider (literally, to be with the stars) whether he has a point. In the Winter 2019 Memberletter, he argued that we need to take precession into account when calculating the date of the U.S. Pluto return. You can disagree with him, but he takes the approach of being persuasive rather than adamant about which zodiac to use. 

The Western Sidereal Astrology Interpretation Workbook is not a book to sit and read. It’s the workbook for the author’s course, and for those interested in really learning Western sidereal astrology in depth, there’s no better resource. For those with a more casual interest in the topic, Bowser’s book, An Introduction to Western Sidereal Astrology is a good starting point, and in fact that book is required (along with others, and software) for the course.

After an introduction that explains how to use the book and some principles of interpretation, there follows a section containing 25 anonymous charts for the student to interpret. The student isn’t left on their own with only a blank sheet to work with, but is guided by a series of questions that are specific to the chart. Those questions address common factors like the signs of the Sun and Moon (sidereal Sun and Moon, of course), as well as more complex factors such as mundane aspects (aspects in mundo, such as when one object is rising as another is culminating) and the use of fixed stars.

In the next section of the book, we learn whose charts we have been working with, and the author gives his interpretation of the first 24 charts, against which the student can check their understanding. The last chart is discussed in a two-hour private lesson with Bowser—certainly a worthwhile experience for any serious student of Western sidereal astrology. Even with very limited experience of sidereal astrology, I found the author’s interpretations to be interesting and insightful. I can’t say that I fully understood the astrology (because I didn’t take the course), but even as a devout tropicalist I was intrigued by the use of the techniques, and particularly the incorporation of the fixed stars.

For those with a serious interest in learning Western sidereal astrology, I have to endorse this as the best possible resource. It’s an opportunity to learn with a true master of the system, and that alone makes it worth the cost. Dilettantes like myself are warned off by the commitment required, but dedicated students will receive excellent guidance.

By Sara Diamond

I approached this topic a bit daunted and with Beginner’s Mind. I’m in just my eighth year of astrological study, and this is my first brush with western sidereal. 

The Western Sidereal Astrology Interpretation Workbook, (the “Workbook”) which goes with Kenneth Bowser’s foundational book, An Introduction to Western Sidereal Astrology, persuades me of one of the author’s main points: that both tropical and sidereal astrologers can and should benefit from the use of in mundo or mundane aspects, which are tied to the Earth’s rotation on its axis and measured in right ascension and declination. To miss using mundane aspects may mean missing the uniqueness of someone’s chart.

Kenneth Bowser is a 50-year master of the history and art of astrology and a leading western sidereal expert. An Introduction to Western Sidereal Astrology, now in its third edition (2021), is the text for his course on the subject, which uses the Workbook. Also required for the course are Bernadette Brady’s Book of Fixed Stars, Vivian Robson’s The Fixed Stars and Constellations in Astrology, and Janus software which generates a speculum, the tool used to quickly spot mundane aspects. The course includes a two-hour private tutoring session with Kenneth. The Workbook is based on charts of 25 unidentified famous people with prompts for students to write up key features, before then going to Section 2 where Kenneth reveals whose charts they are. 


Without telling whose charts are used, the essays for each of these 25 charts are enhanced by Kenneth’s use of fixed stars and mundane aspects, integrated with zodiacal aspects. The intricacies of the interpretations are worth reading even on their own. 

One example I can note here is in the Workbook’s introduction. Using only the zodiacal aspects of Napoleon’s chart, we see his Jupiter/Uranus opposition. But adding the use of the speculum shows the mundane square between the Sun, Jupiter and Uranus, all three simultaneously angular at the latitude of Napoleon’s birthplace on the day of his birth.

For a recent example of how Kenneth works, go to his February 7, 2021 YouTube video called Mundane Aspects. Using Kamala Harris’ chart, zodiacal aspects include her Mars/Jupiter and Jupiter/Saturn squares with Saturn at the MC. Adding use of the speculum read-out shows that when royal star Regulus—associated with high-level prominence—rose in Oakland on the day of Harris’ birth, Jupiter was culminating and Saturn setting, tying all three together angularly in a powerfully unique way.    

With each interpretation, his point is not to minimize the aspects every astrologer looks at but to add from the sidereal toolkit the use of fixed stars and the speculum-generated mundane aspects. 

Kenneth Bowser is good at explaining things. Between his foundational book and the course Workbook, I’m persuaded that, ideally, mundane aspects should get more attention. Regardless of which zodiac one uses, the books and the course are something any serious student may want to add to their list for future study.