Average Daily Motion of Planets in Horary

There is a discrepancy in the horary literature about the average daily motion of the planets, specifically with regard to Mercury and Venus.  The problem arises because from a geocentric viewpoint, Mercury and Venus travel in “epicycles” around the Sun.  Thus, the triune system of Sun-Mercury-Venus travels annually around the Earth at a mean rate of 00d 59m 08s per day, and each member of that system is allotted an average daily motion of 00d 59m 08s from the point of view of an observer on Earth.

The results of this approach are summarized by William Lilly in the following list (in Chaldean order) of the average number of degrees, minute and seconds traveled daily by each planet:

Saturn – 2 minutes 1 second
Jupiter – 4 minutes 59 seconds
Mars – 31 minutes 27 seconds
Sun – 59 minutes 8 seconds
Venus – 59 minutes 8 seconds
Mercury – 59 minutes 8 seconds
Moon – 13 degrees, 10 minutes, 36 seconds

Horary astrologers other than Lilly sometimes used as the average daily motion of the planets different values for Mercury and Venus.  For example, Ivy Jacobson-Goldstein used the following list in Horary Astrology Simplified (p. 5):

Saturn – 2 minutes 0 second
Jupiter – 4 minutes 59 seconds
Mars – 33 minutes 28 seconds
Sun – 59 minutes 8 seconds
Venus – 1 minutes 12 seconds
Mercury – 1 minutes 23 seconds
Moon – 13 degrees, 11 minutes

I believe that Jacobson made a typo with Mars; she must have meant to write 31 minute 28 seconds. The values for Mercury and Venus, however, are not typos; they represent an alternate view of mean planetary motion.  Let me explain.

To arrive at Lilly’s table, you take the distance traveled daily by each planet, adding that distance when the planet is direct and subtracting that distance when the planet is retrograde with respect to the Earth.  Thus, in the course of a year, the Sun, Mercury and Venus all travel an average of 00d 59m 08s, because they travel as a triune unit around the Earth.

Ivy Jacobson-Goldstein, respecting the origins of astrology in a geocentric universe, decided to use Ptolemy’s notion of epicycles to find the average daily motion of the planets.  In this system, the Sun is always traveling in direct motion around the Earth, and Mercury and Venus are revolving around the Sun; thus, these two planets will be covering more distance each day than does the Sun.  It’s kind of like walking your dog; you go in a straight line but your dog goes in circles around you, thus traversing a lot more distance than you do during the walk.

[image error]

In this system of epicycles, imagine that the red dot is Mercury or Venus which travel around the Sun.  The Sun is the little blue dot orbiting around the Earth at a rate of 00d 59m 08s per day.  Mercury and Venus are traveling at that same rate PLUS they have their own daily motion around the Sun, so that the average daily DISTANCE covered by Mercury and Venus is more than that covered by the Sun.  In other words, the Sun simply has to travel in its orbit, whereas Mercury and Venus must travel along with the Sun around the Earth and must additionally travel in their own circles (epicycles) around the Sun.

To get Ivy’s values for Mercury and Venus, you would take the angular distance traveled by Mercury and Venus daily, regardless of whether they were direct or retrograde.  You just want to know the distance traveled, so you don’t subtract for retrograde motion.  It’s like using a pedometer.  If you go for a 1 mile walk to and from your home, you have traveled two miles.  You don’t go + 1 mile away from home and – 1 mile to return to your home, for an average distance of 0 miles walked.  You have actually traveled 2 miles.  (In mathematical terms, you add the absolute values of the distances traveled.

When you add the absolute values for Mercury and Venus traveled each day for one year, you come up with figures of about 1d 12m daily for Venus and 1d 23m for Mercury.  The resulting table is consistent with the one that Deborah Houlding published in 2007, which I have slightly modified below:

PLANET
Mean Daily Distance Traveled


Sun
0° 59′ 08″   or    0.985555 degrees per day


Moon
13° 10′ 36” or  13.17666 degrees per day


Mercury   *
1° 23′         or    1.3833 degrees per day


Venus     *
1° 12′         or    1.2 degrees per day


Mars
0° 31′ 27″   or    0.5242 degrees per day


Jupiter
0° 4′ 59″     or    0.0831 degrees per day


Saturn
0° 2′ 01″     or    0.0336 degrees per day


Uranus
0° 0′ 42″      or   0.026666 degrees per day


Neptune
0° 0′ 24″      or   0.006668 degrees per day


Pluto
0° 0′ 15″      or   0.0041666 degrees per day

* – “Since Mercury and Venus create epicycles around the Sun, their annual average distance travelled through the zodiac will equal that of the Sun.” — Deborah Houlding.

To test this out, I picked 5 ten-day periods throughout the years from 2000 to 2005 in the Swiss Ephemeris and calculated the number of degrees traveled by Mercury, Venus and Mars during those times to find an average number of degrees per day.  Here are the results of this small sample in an Excel Spreadsheet:

Average Daily Motion of Planets – Degrees per Day – (sample of 50 days per planet)







Avg for
Mercury
Venus
Mars




January-00
10-days
1.58166
1.21333
0.775




May-02
10 days
0.81666
1.33166
0.67




July-03
10 days
2.15166
1.22333
0.275




September-04
10 days
0.485
1.068333
0.638333




November-05
10 days
0.835
0.98666
0.35166






Mercury
Venus
Mars






Degrees per day
Degrees per day
Degrees per day



Average


1.173996
1.1646626
0.5419986






1d 10m 27s
1d 9m 53s
0d 32m 31s

Most astrology software will give planetary speeds.  There is an online calculator that will give basic ephemeris data for any date and time from 1500 – 2099, including planetary speeds, at https://serennu.com/astrology/ephemeris.php