What Is the Imum Coeli (IC) in Astrology?

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The Imum Coeli, or IC (Latin for "lowest part of the sky"), is the chart angle opposite the Midheaven (MC): the ecliptic's lower-culmination crossing of your local meridian, always the same degree in the opposite sign. Away from polar latitudes that point usually lies below the horizon; in polar regions the IC can sit above the horizon when the upper-culmination MC is below it. Astrologers often read it for roots, home, family background and the private base a person builds from.

Like the other chart angles, it is a point, not a planet or a house, and it needs a reliable birth time and place.

Where the IC sits

Picture the meridian as a circle running through the point overhead and on beneath your feet. By convention the Midheaven is the upper-culmination crossing of the ecliptic on that meridian, and the IC is the opposite, lower-culmination end. In nonpolar circumstances the upper end usually sits above the local horizon and the lower end below it, on the far side of the Earth from your view of the sky. That familiar above/below picture is not universal: in polar regions the upper-culmination MC can fall below the horizon and the IC above it. The IC is still defined as the opposite of the MC, not as whichever meridian end happens to be below the horizon. Because the two points are opposite ends of one axis, they always move together: when the MC changes sign, the IC changes sign at the same moment.

That gives you a simple check. If you know your true MC, you know your IC:

The table also works in reverse, so a Libra MC has an Aries IC, a Pisces MC a Virgo IC, and so on. The degree is the same at both ends: an MC at 3°32' Pisces puts the IC at 3°32' Virgo.

IC, 4th house and 4th ruler

The IC is often confused with two neighbouring ideas:

• The 4th house is the sector that opens at the IC in a Placidus chart. A planet placed there, such as the Moon in the 4th house, is read through home, family and private life.
• The ruler of the 4th house is the planet that rules the sign on the 4th cusp. Reading it follows the general method in house rulers explained.

With Placidus houses, which the calculator uses unless the birthplace lies beyond 66° of latitude, the 4th cusp and the IC coincide. With the Equal houses used beyond that line they generally do not, which is why the IC needs its own care at high latitudes.

What the IC is often read for

The IC is the most private of the four angles. Common readings include:

• the family atmosphere or background a person grew up with, as they experienced it;
• what helps them feel settled, and what "home" needs to include;
• the inner foundations that public aims rest on, the other end of the MC's direction;
• in later life, the kind of base or retreat they tend to build.

The IC sign colours these themes. A Cancer IC is often read as needing emotional closeness at home; a Capricorn IC as finding security in structure and responsibility; an Aquarius IC as wanting room to be different within the family or to build a chosen one. Some astrologers also link the IC with one parent, though traditions disagree about which, so that reading is best held loosely.

None of this describes a family as it actually was. Two people with the same IC can come from very different homes. The chart offers themes to compare with experience, not a record of it.

Reading the IC with the MC

Because the axis runs from private roots to public aims, astrologers usually read both ends together. A Leo MC with an Aquarius IC might be read as a wish to be recognised for something personal and expressive, resting on a need for independence at home. A Capricorn MC with a Cancer IC might be read as ambition built to protect what feels like family. The point is the tension or balance between the two ends rather than either sign alone.

Birth time and the IC

The IC moves at the same pace as the Midheaven, which varies through the day. In Amsterdam on 15 April 2001, the calculator places the IC at 29°34' Gemini at 06:05 and 0°43' Cancer at 06:10, so five minutes moved it across a sign boundary. A recorded time that is rounded to the nearest quarter hour can leave the IC sign open when it falls near the edge of a sign. How accurate your birth time needs to be shows how to test a time window, and birth time rectification explains why an estimated time stays an estimate.

When no birth time is entered, the wheel leaves out the IC along with the MC and every house line.

Finding your IC on the free chart

Calculator limitation at high latitudes: For births more than 66° north or south, Astrologist.com uses Equal houses from the Ascendant. In these charts, the wheel currently labels the 10th-house cusp ‘MC’ and the 4th-house cusp ‘IC’. Those labels do not identify the true Midheaven and Imum Coeli: the true angles can fall at different degrees and in different signs. The calculator does not currently display the true MC or IC for these charts. Do not use these two labels to identify your MC or IC placement. This particular labeling limitation does not affect the ASC/DC labels.

1. Enter your date, place and exact time in the free birth chart.
2. Read the house system printed below the wheel. Only a Placidus chart shows your true IC; if it reads Equal, the reasons are set out in chart angles at high latitudes.
3. Look for the IC label around the rim. Ignore where it lands on your screen: the Ascendant is always drawn on the left, and the IC is drawn at its calculated degree, opposite the MC.
4. Your IC sign is the zodiac segment lying just inside that label. Cross-check it against the MC with the table above.

For a conversation about what your IC and MC axis may suggest, the Astrologist can help.

Related articles

• Chart Angles Explained
• What Is the Midheaven (MC)?
• Moon in the 4th House
• House Rulers in Astrology
• Why Birth Time Matters
• The Angular Houses