Caption: This diagram illustrates the ancient astronomy lore of planetary configurations.

Features:

1. Planetary configuration can be defined as the apparent position of a planet (i.e., its angular position position as seen from the Earth) relative to the Sun and the relationship of this apparent position to the 3-dimensional position of the planet in the Solar System.

2. The planets are inferior planets---lowly, degraded planets---if they are inward of the the Earth's orbit and superior planets---lordly, conceited planets---if they are outward of the Earth's orbit.

3. The planetary configurations shown are conjunction (inferior conjunction, superior conjunction), opposition, greatest elongation (greatest eastern elongation, greatest western elongation), and quadrature (eastern quadrature and western quadrature).

4. Conjunction is when a planet is aligned with the Sun on the sky: i.e., on the Earth-Sun line. An inferior conjunction is when it is nearer than the Sun and superior conjunction when it is farther.

   Superior planets can only have superior conjunction which are then usually just called conjunctions

5. Opposition is when a superior planets is 180° away from the Sun on the sky. It is opposite the Sun on the sky. A planet in opposition rises when the Sun sets and sets when the Sun rises.

   Inferior planets can never be in opposition.

6. Greatest elongation is when an inferior planetsSun in angle on the sky as it can be. Superior planets do NOT have greatest elongations. The have oppositions.

7. Quadrature is when a superior planets is 90° away from the Sun Inferior planets do not have quadratures.

8. The diagram omits syzygy, good old syzygy, old syzygy---an alignment of 3 astro-bodies in a gravitationally bound system.

9. The diagram also omits apparent retrograde motion which can be considered a planetary configuration if one stretches the terminology a bit.

10. Planetary configurations were important in the old days in establishing the orbital elements (AKA parameters) of the planets.

    They are part of the ancient lore of astronomy.