One of a planet's four lines on the map: MC, IC, AC or DC.
Midheaven and Imum Coeli lines are meridians, so they run straight north to south. Ascendant and Descendant lines are curves, because a planet rises at different longitudes depending on latitude — and they break off where the planet does not rise at all, like the summer Sun above the Arctic Circle.
Why the curves break off
An Ascendant line joins the places where the planet was rising at the moment you were born. But not every planet rises at every latitude. It depends on declination, meaning how far north or south of the celestial equator the planet lies: the higher it is, the wider the band near the poles where the planet stays permanently above or below the horizon.
There the curve has no solution and stops. Before it disappears, the planet's Ascendant and Descendant lines draw together until they meet on its Midheaven or Imum Coeli line. This is not a flaw in the drawing: it is the geometry of the sky as seen from that latitude.
How to read the map
A planet's Midheaven and Imum Coeli lines are always 180 degrees of longitude apart, on opposite sides of the globe. At the equator, the Ascendant and Descendant lines fall 90 degrees from the Midheaven line; moving away from the equator they bend, and the further the planet is from the celestial equator, the more they bend. A planet with high declination has steeply curved lines, one close to the celestial equator has almost straight ones.
Where lines of two different planets cross, both planets were angular at the same moment, and the spot is read as a blend of the two meanings. On the SideraMea map, Midheaven and Imum Coeli lines are solid, Ascendant and Descendant lines dashed.
Frequently asked questions
What does a Saturn line through my city mean?
Astrologically it is read as a place where Saturn's themes come to the fore: responsibility, structure, long-term commitment, but also effort and a sense of limits. It does not mean things will go badly there. Traditionally it is described as a place where you work hard and build something solid, at a cost you can feel.
Do planetary lines change over time?
Natal lines do not: they capture the sky at the moment of birth and stay put for life. What changes is how you experience them as your life moves through its stages. Some astrologers also draw lines for transits or the solar return, but those are different maps, tied to a different moment.
What is the difference between an Ascendant line and a Descendant line?
The Ascendant line joins the places where the planet was rising in the east when you were born; the Descendant line, the places where it was setting in the west. Astrologically the first concerns how you come across and how you start things, the second your relationships with others: partners, associates, whoever stands opposite you.
See it in your own chart
Calculating your birth chart is free: wheel, planets, houses, aspects and a first reading. All you need is your date, time and place of birth.