The Venus Line in Astrocartography

Obama's birth certificate puts his birth at 7:24 PM in Honolulu on August 4, 1961, which was 05:24 UTC the next day. Venus was at 1°47′ Cancer, a morning star rising ahead of the Sun. The site's API, called the way the astrocartography map calls it, returned the four lines below, and a script compared each of their points with the Swiss Ephemeris before measuring the distance from every city in the site's list.

Venus orbits inside the Earth's orbit, so it never appears far from the Sun: its greatest elongation, the widest angle it opens from the Sun, is about 46° to 47°. When it is west of the Sun it rises before dawn as the morning star, and when it is east it sets after dusk as the evening star. On a map the same tether holds the lines: each Venus line runs within reach of the matching Sun line. In our scan of every day from 1900 to 2050, the widest separation between the Venus MC line and the Sun MC line was 50°58′ of longitude, on November 29, 1917: a little more than the elongation, because the zodiac meets the equator at an angle.

Obama's Venus was 40°45′ west of the Sun, near the morning-star end of its range, and its meridians sit 43°03′ to the west of the Sun's. It had been retrograde in the spring of 1961, stationing retrograde on March 20, 1961 at 29°05′ Aries and direct on May 2, 1961 at 12°44′ Aries; by August it was well clear of the Sun and moving 1°08′ a day. So if you know only that your Venus was a morning or an evening star, you already know which side of your Sun lines to look for it.

The shape of a rising or setting line depends on the declination of the planet's zodiac degree, how far north or south of the equator that degree lies in the sky. A degree near 0° Aries or 0° Libra sits on the equator and gives almost straight rising and setting lines; a degree near 0° Cancer or 0° Capricorn is as far from it as the zodiac goes and gives the most strongly curved ones. Obama's Venus at 1°47′ Cancer is just past the solstice point, with a declination of 23°25′ north, almost the full tilt of the Earth's axis.

The result shows in the table. Between 60° S and 60° N his Venus rising line swings through 97°17′ of longitude. His Mars, at 22°34′ Virgo, has a degree only 2°56′ north of the equator and a rising line that moves just 10°13′ over the same range. At 66° N, the top edge of the map, the Venus rising line has bent to within 13°15′ of the Venus IC line, the start of the hook such lines make near the polar circle, where a degree this far north barely sets.

The site's lines are zodiacal: they follow Venus's degree on the ecliptic and set aside its latitude. Jim Lewis drew his maps from the planet itself, in mundo. For Venus the difference can be large, because when Venus passes between the Earth and the Sun it is only about a quarter of an astronomical unit away and its small orbital tilt looks large from here. In our scan from 1900 to 2050, its greatest distance north of the ecliptic was 8°43′ on March 13, 2049, with Venus 0.28 AU from Earth and 3°54′ from the Sun; the southern record, 8°43′, came on September 12, 1919.

Someone born in those weeks has Venus lines whose two versions sit far apart. Obama is not one of them. His Venus was 1.06 AU away and 1°47′ south of the ecliptic. Because it sat near the solstice, almost all of that latitude went into declination rather than right ascension, so the meridian lines barely move (0°01′); the curved lines move by up to 290 km at 60° N:

Jim Lewis's own figure for a line's reach grew over time. His 1976 handbook spoke of a quarter of an inch either side on his maps, roughly 300 to 400 miles; his 1982 Cyclo*Carto*Graphy handbook said experience suggested up to 700 miles. Even at that widest setting, Obama's four Venus lines reach just 304 of the site's 2,292 cities (13%), the fewest for any of his ten planets, because two of the four spend nearly their whole length at sea.

A time error moves all four lines together, 0°59′ west for every four minutes, so a West Coast city that sits 8 km from the line on a correct birth time could be well off it on a time rounded to the nearest half hour. Check the birth time before choosing between nearby cities, and use the pre-filled map to see how the Venus lines sit beside his Sun and Mars lines.