LIBRA, the constellation the Balance, the seventh sign of the zodiac and the day house of Venus, is the exaltation or sign of maximum power of Saturn and the depression or sign of minimum power of the sun (Tetrabiblos I.17, 19) and the hot and moist sign (Confessio Amantis VII.1111-1120). It lies in the southern hemisphere between Scorpio in the south and Virgo in the north. Libra, which the sun enters on September 21 in modern times, is the autumn or fall equinox as Aries is the spring equinox.

The narrator makes an error when he says that Libra is the moon's exaltation, or sign in which the moon is most powerful, ParsP 1-11. Sigmund Eisner points out that the narrator means that Libra is just a few degrees above the horizon, 3 degrees in its ascent. Libra is the seventh sign of the zodiac, Astr I.8.4. The heads or beginnings of Aries and Libra turn on their circles of the equinox, Astr I.17.14-16; Aries is the spring equinox and Libra is the autumn equinox. When the sun is in the head or beginning of Libra, days and nights are of equal length, Astr I.17.22-23. All the signs moving within the heads or beginnings of Aries and Libra are said to move northward, Astr I.17.26-28. Libra lies directly opposite Aries, Astr II.6.14-15. The beginning of Libra in its equinox is as far from the south of the horizon as is the zenith from the arctic pole, Astr II.22.1-3. To calculate altitude, the altitude of the sun must be measured when the sun is in the head of Libra or Aries, Astr II.25.13-16. To calculate latitude, find the altitude of the sun at noon at the time of the equinox, which can only be done on two days of the year, March 12 and September 12 in Chaucer's day. If it is too long to wait until the sun is in Aries (spring equinox) or Libra (autumn equinox), observe its midday altitude and allow for its declination or celestial latitude (point in the celestial sphere), Astr II.25.34-39. All the signs from the beginning of Libra to the end of Pisces are called southern signs because they lie in the southern hemisphere, Astr II.28.37. The sun never rises due east unless it is at the beginning of Aries or Libra, in the spring or autumn equinox, Astr II.31.3-6. [Aries: Lenne: Venus]

The name appears once medially, ParsP 11, and in the prose of the Astrolabe.