How to Read an Ephemeris

Components of the Ephemeris

An ephemeris (eh fem’ er iss) is a reference book showing precisely when certain celestial phenomena occur. These instructions apply to the most popular type of ephemeris, published by ACS Publications. Their ephemerides (that’s the plural of the word) are available in either half-century or century books with the option of positions listed at noon or midnight Greenwich Mean Time (GMT), the worldwide standard in England.

You will need to know the symbols for the Sun, Moon, planets, lunar phases, lunar nodes and the signs. Other than the lunar phases, all these items are on my Astrologer’s Apprentice Cheat Sheet (although my symbol for Pluto does not match the “PL” symbol used in the ephemeris). You should be familiar with the symbols for the lunar phases from most calendars: a black circle for the New Moon, a white circle for the Full Moon, and half-and-half circles for the First and Third Quarter Moons (white on the right for First Quarter, white on the left for Third Quarter).

The times in the ephemeris are expressed in GMT. To convert to your time zone, subtract 4 hours for Atlantic, 5 hours for Eastern, 6 for Central, 7 for Mountain and 8 for Pacific. During Daylight Saving Time, subtract one hour less.

The twelve equal signs of the zodiac are 30 degrees each, measured in celestial “longitude.” The longitude table for each month has columns for various celestial factors and a row for each day. (You can ignore the “Sid. Time” column unless you’re calculating a chart “from scratch.”) A position is listed in this order: degree, minute (1/60th of a degree) and in the case of the Sun and Moon, the second (1/60th of a minute). These are measurements in space, not to be confused with clock time. The minutes (other than for the Sun and Moon) use a decimal fraction. The Moon moves so quickly it’s listed at both midnight (0 hr) and noon in the midnight ephemeris. The other planets’ positions are listed at midnight GMT. When planets are Retrograde (appearing to move backwards through the zodiac) as a month begins, the second line of the month says R. The column is shaded when the planet is Retrograde and a D shows the day it turns Direct. The position is also listed for the Moon’s North Node. (The South Node is always the same degree and minutes of the opposite sign.) The table shows its “true” position, which alternates between Retrograde (normal for it) and Direct. Many astrologers only use the Mean (average) position for the Nodes (see below), which is always Retrograde.

The ephemeris shows the exact date and time a planet enters a sign in the “planet ingress” list at the bottom. A space separates the two months that share the page. The “Astro Data” column on the left tells you when planets turn Retrograde (R) or Direct (D) and when two outer planets have an aspect. The degrees of these phenomena are not listed here, but you can “ballpark” them from the row for the applicable date. (You can ignore the items showing when planets rise above (N) or below (S) the “celestial equator,” the middle of the zodiac path.)

The “Last Aspect” and “Ingress” columns list the time that the Moon makes its last aspect in a sign, becoming Void of Course, and when it enters the next sign, ending the Void period. (A Moon Void of Course period is the time after the Moon makes its last aspect in a sign until it enters the next sign. It is considered a time of buyer’s regret, not good for major purchases, decisions or beginning something new.) Here you can see the Moon’s last aspect, an influence that continues throughout the Void period. The “Phases & Eclipses” box lists the main phases of the Moon: New, First Quarter, Full and Last Quarter. First it states the day of the month, then the time, then the phase, and last the zodiac degree, sign and minutes where it occurs. New and Full Moons that aspect anything in your chart within a couple of degrees can have a big influence for you.

A second “Astro Data” box on the right has information you may not need, like the SVP (related to Indian astrology) and the Julian Day (number of days since the century began). It also lists some useful data: the zodiacal longitude on the first of the month for Eris (the new planet out past Pluto) and the asteroids Chiron, Pallas Athena, Juno and Vesta, along with the Mean (average) position of the Moon’s North Node. The symbol for Chiron looks like a K over a sideways oval. The symbol for Pallas Athena is a vertical diamond on top of a cross. Juno’s glyph looks like an asterisk on top of a cross and Vesta’s glyph looks like a V with a flame rising up from it.

Relating the Ephemeris to YOUR Chart

Now that you’re familiar with the types of information in the ephemeris, how do you figure out when planets affect YOU? Look for aspects to your birth chart. These occur when a moving (“transiting”) planet reaches the same degree as one of your natal planets. To figure out the type of aspect, you’ll need to look at the order of the signs in the zodiac, from Aries to Pisces. The aspect depends on the sign of the transiting planet relative to the natal planet: same sign = conjunction; the sign immediately before or after = semisextile; 2 signs before or after = sextile; 3 signs before or after = square; 4 signs before or after = trine; 5 signs before or after = quincunx (also called an inconjunct); 6 signs away = opposition. Another type of aspect occurs when the transiting planet is 1-1/2 signs before or after (semisquare) or 4-1/2 signs before or after (sesquiquadrate). These are harder to spot. Allow up to five degrees leeway (the astrological term is “orb”), although the closer to exact, the stronger the influence.

For example, look at your birthday. The degree of the Sun is the same every year on that date (within a degree). Now you can look for other dates in the year when a planet goes through the same degree of the same sign and you’ll know that planet is activating your Sun’s potentials, strengthening or adding to how you express your purpose and intentions. If any planet is within 5 degrees of a sign three or six signs away, your Sun is receiving a square or an opposition, and that time frame should hold challenges for you personally; you may not get the glory you deserve around then or be able to wield your usual influence. This same process can be applied to any planet in your chart. Aspects from transiting planets amplify what your natal planet signifies by its sign and house positions and its natal aspects. If the transiting aspect is a helpful one, the outcome should be positive with a smooth experience. If the aspect is a difficult one, then your experience is likely to be more stressful or require you to work harder to obtain a happy result. Even a helpful positive aspect to your natal planet from a transit can be problematic if your natal planet is embroiled with difficult aspects in your natal chart.

Find the planetary stations (when a planet turns Retrograde or Direct) and check if any planets change direction in an aspect to anything in your chart. If so, you’re apt to experience a slow-down in the activities associated with your natal planet when the transit stations. The nature of the transiting planet describes the pressures applying to your life and the type of aspect hints as to whether the experience will be pleasant or trying. For instance, if you receive a square from stationing Saturn, obstacles will slow your progress in the area(s) associated with the receiving planet. If you receive a trine from Jupiter, your path should be nearly bump-free for the part(s) of your life that Jupiter affects. Be sure to look for your natal house starting with the sign that your receiving planet rules. Thus if your Mars receives an aspect, look at your house that starts with Aries. A list of the rulers of the signs is in my Study Booth for Beginners.

GOOD LUCK! If you can work with an ephemeris, you’re on the way to being a real astrologer.