R:

Radix (Radical): a natal planetary position or chart.

Resolution: the quality of being able to separate or distinguish close objects from each other. The ability of a telescope to resolve the component stars of a distant galaxy or a multiple star system is directly proportional to the diameter of its aperture, i.e., how wide its lens or mirror is. The unaided human eye can resolve objects in detail about 1 arc minute across. Telescopes in the mid-20th century were capable of resolving images to 1 arc-second: the size of a dime seen from 2.3 miles away. The Hubble Space Telescope increased that resolution to about 0.1 arc-second, and the advent of radio telescopes has allowed astronomers to resolve images as fine as 0.001 arc-seconds. VLBI (or Very Long Baseline Interferometry) is a technique used by radio astronomers to obtain extreme detail. Instead of using a single radio dish, telescopes are linked together in arrays across whole countries or even continents. When the signals are combined in a specialized computer, the resulting image has a resolution equal to that of a telescope whose diameter is equal to the separation of the component antennas that are furthest apart.

Retrograde: the apparent backward motion of a planet against background stars as seen from Earth. Someone with retrograde planets is redoing those planets’ functions in a highly personal, individualistic sense. Things manifest more slowly for a retrograde planet; one is more subjective and thinking more deeply about it. The retrogradations of Mars, Venus, and Mercury, in that order, are the most significant. The retrogradations the outer planets, Uranus, Neptune and Pluto are not as personally significant because they are retrograde about half the time.

Right Ascension: the arc on the celestial equator extending eastward from the vernal equinox to the meridian of the object in question in the equatorial coordinate system. This coordinate corresponds to longitude on the Earth. The other coordinate in this system is called "declination."

Rising (sign): In natal astrology, the sign on the Ascendant (first house cusp). In horary astrology, the sign rising in the east at the time in question.

Rotational inertia: the tendency of a spinning body’s spin axis to remain pointed in the same direction in space. As long as a spinning body is not acted upon by an outside force its spin axis will remain forever pointed in the same direction in space relative to the stars! This is how gyroscopes form inertial guidance systems for planes, submarines and spacecraft. These vehicles constantly refer to a gyroscope’s fixed and rigid orientation in space in order to navigate and maintain their bearings (see pages 89 and 90 in "You and the Universe").

Ruler: the planet that rules a given sign or house

Ruler (of the Chart): the planet ruling the rising sign (Ascendant) is said to be the Ruler of the chart. Thus if you have Cancer (or Gemini) rising, the Moon (or Mercury) is the ruler of your chart.

Ruler (house): A planet is said to rule a house when it rules the sign on the cusp of that house.

Ruler (sign): A planet is said to rule that sign which typifies or characterizes its energy, and in which it expresses itself most freely and naturally. A planet is said to be "dignified" in the sign it rules. The Sun rules Leo; the Moon, Cancer; Mercury, Gemini and Virgo; Venus, Taurus and Libra; Mars, Aries and Scorpio; Jupiter, Sagittarius and Pisces; Saturn, Capricorn and Aquarius; Uranus, Aquarius; Neptune, Pisces; and Pluto, Scorpio. Aquarius, Pisces, and Scorpio were ruled by Saturn, Jupiter, and Mars until their rulers Uranus, Neptune, and Pluto were discovered.