Imum Coeli

Meaning

The Imum Coeli, or IC, Latin for the “bottom of the sky”, is the degree of the zodiac on the meridian beneath the birthplace, always exactly opposite the Midheaven, at the foot of the chart. It is sometimes loosely called the nadir, though the true nadir, straight below one’s feet, usually lies off the zodiac.

In most house systems it begins the 4th house. Astrologers read it as roots and private life: home, family, origins and a parent, the inner ground someone stands on and comes back to. Tradition also read the fourth place as the end of matters, how things turn out.

Where the Midheaven is what someone shows the world, the IC is what holds them up from below, seldom seen by others yet often the base on which a public life rests.

In practice

• Its sign colours the feeling of home: an IC in Cancer often goes with close family ties and a strong need for a home of one’s own, one in Sagittarius with roots found in movement or abroad.
• Planets near the IC shape the early home and private life: Saturn there can describe a childhood with a lot of duty and a later wish to build something solid, the Moon a deep attachment to family.
• Transits over the IC are often read with changes at home or in someone’s sense of belonging, such as a move or a new household.

Across traditions

• Indian astrology reads home, mother and inner contentment from the fourth sign counted from the lagna.
• Human Design does not use the IC or the houses.

Origin and history

Hellenistic astrologers called it the hypogeion, the pivot “under the earth”, and read in the fourth place parents, property and foundations. William Lilly kept that frame in 1647: his fourth house showed the father, lands and houses, and the end of any matter. Psychological astrology, as in Howard Sasportas’s book of 1985 on the houses, turned the IC into the private self and the family inheritance a person carries.

How Ulune calculates it

Ulune places the IC exactly opposite the Midheaven, which it takes from the Swiss Ephemeris’s house calculation; like the Midheaven it does not depend on the latitude, and it changes sign every two hours or so. It is the cusp of the 4th house in Placidus, Ulune’s default, and the other quadrant systems; with equal or whole-sign houses it floats, and Ulune reads its house from the cusps.

No aspect is listed between the IC and the Midheaven, always opposite. Aspects to it use 6° for the trine and 4° for the sextile, and in the calendar a transit to the IC is listed once, as the matching transit to the Midheaven. Without a birth time it is only a noon stand-in, marked approximate.