How Long Each Zodiac Sign Takes to Rise, From the Equator to the Polar Circles

The sky turns once against the stars in 1,436 minutes of clock time, the sidereal day, and every sign of the zodiac crosses the eastern horizon once in that turn. An even split would give each sign the Ascendant for 119.7 minutes. The equator already misses that, with 111.3 minutes for its quickest signs and 128.4 for its slowest. At New York's latitude Aries rises in 71.2 minutes and Leo in 152.6; at Reykjavik's the figures are 12.6 and 216.9 minutes.

The cause is two circles that do not line up. The sky turns about the poles, so equal arcs of the sky's equator cross the horizon in equal times. The zodiac lies on the ecliptic, the Sun's apparent yearly path, which is tilted against that equator, so each sign's thirty degrees carry a different length of the turning equator over the horizon with them, depending on where the sign sits and on the observer's latitude. Ancient astronomers called that arc the sign's ascension (right ascension on the equator, oblique ascension anywhere else), and Ptolemy's Almagest tabulated it for a series of latitude bands.

From the ground, the same cause shows in the angle at which the ecliptic meets the horizon. At a shallow angle a sign lies nearly flat along the eastern sky and many of its degrees come up together; at a steep one it climbs out degree by degree. North of the equator the shallowest moment comes as the start of Aries rises and the steepest as the start of Libra rises, which is why Aries and Pisces are the quickest pair in every northern row of the table.

For an observer on the equator, the sky's equator stands straight up from the horizon, so each sign rises in its span of right ascension. Gemini, Cancer, Sagittarius and Capricorn sit near the solstices, where the ecliptic runs almost parallel to the equator, and take 128.4 minutes each; Aries, Pisces, Virgo and Libra border the equinoxes, where the ecliptic cuts across the equator at its steepest, and take 111.3.

Away from the equator a second effect is added. For a northern observer, a degree of the zodiac lying north of the sky's equator comes up sooner than it would for someone on the equator, and a degree lying south of it later, by a margin that grows faster than the latitude does. From Capricorn through Gemini each degree lies farther north than the one before, so those signs lose time; from Cancer through Sagittarius each lies farther south, so they gain it. Traditional astrology names them the signs of short and of long ascension. At 40 degrees north all six short signs rise in less than 119.7 minutes and all six long ones in more.

Divide the slowest sign's minutes by the quickest's and the result is 1.2 on the equator, 1.4 at 20 degrees north, 2.1 at 40, 6.7 at 60 and 73.3 at 66, where Aries clears the horizon in 3.2 minutes. The slowest pair itself moves: Cancer and Sagittarius up to 22 degrees north, Leo and Scorpio from 23, a four-way tie at 48, Virgo and Libra from 49 to 57, and Leo and Scorpio again above that. At London's latitude Virgo outlasts Leo by only 0.4 minutes.

Quito, 0.2 degrees south, and Singapore, 1.4 degrees north, keep close to the equator's figures: no sign in either city takes under 110.2 minutes or over 128.7. By Mumbai, at 19.1 degrees north, Aries and Pisces are down to 95.3 minutes and Cancer and Sagittarius up to 133.7.

Los Angeles gives Aries 79.9 minutes and Leo 145.1; New York, 6.7 degrees farther north, 71.2 and 152.6. London, at 51.5 degrees, falls in the band where Virgo and Libra are slowest, at 170.3 minutes, while Pisces takes 52.4, so a Libra Ascendant there lasts 3.3 times as long as a Pisces one. Stockholm gives Aries 31.5 minutes, and Reykjavik, the most northerly city here at 64.1 degrees, 12.6, while each of the six long signs holds the horizon for at least 3 hours 5 minutes.

Below the equator the geometry runs in mirror image: at each southern latitude a sign rises in the time its opposite sign takes at the same northern latitude. Taurus at 34 degrees south takes 145.1 minutes, as Scorpio does at 34 north; Virgo at 66 south takes 3.2, as Pisces does at 66 north. In Sydney, Buenos Aires and Johannesburg, Virgo and Libra therefore rise quickest and Taurus and Aquarius slowest, 80.1 against 145.0 minutes in Sydney.

The switch happens at the equator itself. Quito, only 0.2 degrees south, already has Virgo quicker than Aries (111.2 against 111.5 minutes), and Singapore, 1.4 degrees north, the reverse (110.2 for Aries against 112.4 for Virgo). Longitude plays no part: Sydney and Buenos Aires, on different continents but within 0.7 degrees of latitude, differ by under a minute for every sign. A time zone moves the clock time at which a sign comes up, never how long it stays.

Only some of the traditional labels survive the trip south. Ptolemy's Tetrabiblos calls signs placed evenly on either side of an equinox commanding and obeying because they rise in equal times, and Taurus and Aquarius tie in Sydney just as they do in London. The long and short labels hold for northern skies alone: in Johannesburg Aquarius, a short sign in the old books, takes 137.9 minutes and Leo, a long one, 100.7, against an even share of 119.7.

If births spread evenly through the year, a sign's share of the sidereal day is also its expected share of the births at that latitude. Births bunching at certain clock hours does not change this, because sidereal time gains 3.9 minutes on the clock each day, so every clock hour passes through every sign within the year. At Stockholm that predicts Leo rising for 13% of births and Aries rising for 2.2%, about one chart in 46; at Reykjavik the Aries figure falls to about one chart in 110.

That base rate matters to anyone counting rising signs in a group of charts. People born in northern Europe would show more Leo, Virgo, Libra and Scorpio Ascendants than Aries or Pisces ones from the sky alone, so an excess of those signs among, say, famous people means little until each birthplace's expected share is set beside it. At London's latitude those shares run from 3.6% for Pisces to 12% for Libra, against an even 8.3%.

The minutes also set how far a birth time can drift before the rising sign changes. London's Pisces passes a degree every 1.7 minutes on average and its Libra one every 5.7; at Reykjavik a degree of Aries goes by in about 25 seconds, so a time rounded to the nearest quarter hour could miss the sign entirely. Medieval textbooks called the quick signs crooked and the slow ones straight. Modern astrology books describe an Aries or Leo Ascendant with no allowance for latitude, though at Reykjavik's the second should turn up 17 times as often as the first.

The table gives every fifth degree, north first. The row nearest a birthplace's latitude shows how long each sign holds the eastern horizon there, and so how often each rising sign should turn up among births in that place. Near London one degree of latitude moves Aries by 2.2 minutes, so values between rows can be read by eye.

Toward the ends the rows change faster: from 60 to 65 degrees north Aries falls from 29.3 minutes to 8.4, and at 66, the last degree calculated, to 3.2. Past the polar circles some degrees of the zodiac never rise at all and the Ascendant jumps across them, so the calculation stops at 66 and the table at the fifth degree before it.

Precise astronomical calculations followed the Ascendant at each whole degree of latitude through one sidereal day from the J2000.0 epoch, noon Terrestrial Time on January 1, 2000, solving for the moment it entered each sign. A sign's minutes are the clock time from its entry to the next sign's; its share is those minutes over the 1,436-minute day. The cities were worked the same way at their own latitudes.

Only the tilt of Earth's axis ties the figures to a year. Tropical signs are counted from the March equinox, so precession, which drags the equinox back through the constellations, carries the signs along with it; a sidereal zodiac, fixed to the stars, would see its rising times drift over the centuries. The tilt changes slowly enough that births a century apart get figures within a minute of each other. The shares assume births spread evenly over the year, and they describe the rising sign only: the exact degree and the houses need a recorded time.