The Pluto Line in Astrocartography

The site's lines are zodiacal: each one is drawn for the point of the ecliptic at the planet's longitude. For most planets that point and the planet are close together. Pluto's orbit, though, is inclined about 17° to the ecliptic, and from the Earth it can appear well off it: in our day-by-day scan from 1900 to 2050 its latitude reached 17°43′ north on April 11, 1980, in the decade before its closest approach to the Sun in 1989, and 13°20′ south by September 8, 2050.

At Obama's birth Pluto stood 12°33′ north of the ecliptic at 6°58′ Virgo. That raised its declination to 20°34′ north, against 8°57′ for its zodiac degree: a gap of 11°36′, enough to change when it rose and set at 45° latitude by more than half an hour. Even the meridian lines move. Calculated from Pluto's own position (in mundo), the method of Jim Lewis's maps, the MC and IC lines would sit 4°56′ east of the site's, about 549 km at the equator, the largest such shift of his ten planets. The rising and setting lines move much further:

Different lines, different cities

The shift is big enough to swap one set of cities for another. The site's Pluto rising line passes Stockholm, Warsaw, Bucharest, İzmir and Alexandria. Drawn in mundo it would run through central Europe instead, past Hamburg, Prague, Munich, Vienna and Sarajevo, before reaching Africa, passing near Khartoum, and running on toward Mombasa and Antananarivo. His zodiacal Pluto setting line touches no city in the site's list at all; the in mundo one runs down western North America past Edmonton, Calgary and Spokane to the San Francisco Bay Area.

A check in Honolulu

The birthplace shows the same gap in time. By the site's map, Pluto's zodiac degree set in Honolulu 1 hour 2 minutes after the birth. Swiss Ephemeris timing of Pluto itself gives 9:05 PM: Pluto set 1 hour 41 minutes after Obama was born, 39 minutes later than the zodiacal line implies. Being 12°33′ north of the ecliptic, Pluto stayed above the western horizon well after its degree had gone down.

Neither map is wrong. The zodiacal line answers the question a relocated chart asks, where Pluto's degree sits on an angle; the in mundo line answers where Pluto was actually on the horizon or the meridian. But no other planet makes the choice matter this much, so it is worth knowing which kind of map you are reading before deciding a city is or is not on your Pluto line.

Here are the four zodiacal lines the site's API returns for Obama's birth (7:24 PM, August 4, 1961, Honolulu, per his birth certificate; 05:24 UTC), the ones the astrocartography map draws for him. Every point was confirmed with the Swiss Ephemeris, and the city distances are measured to the lines as drawn.

Clyde Tombaugh found Pluto at the Lowell Observatory in Flagstaff, Arizona, on February 18, 1930, by comparing photographs of the same star field taken days apart; the find was announced on March 13 of that year. In 2006 the International Astronomical Union classed Pluto as a dwarf planet. Astrologers kept it, along with the meanings they had given it since 1930, and astrocartography maps still draw its four lines alongside the others.

Pluto's orbit is long and lopsided as well as tilted: it takes about 248 years to go around, spending anywhere from about a dozen to about thirty years in a sign. In 1961 it was in Virgo, moving forward from 5°32′ Virgo, where it had stationed on May 17, 1961, toward 10°07′ Virgo, where it would station again on December 12, 1961. In Obama's chart it sits between Uranus, whose MC line runs 11°09′ to the west, and Mars, 14°28′ to the east, and however slowly Pluto moves, the Earth's rotation still sweeps its lines around the world: a birth half an hour later would have put the Pluto MC line through Beijing and Tianjin and the rising line through Berlin, Vienna and Budapest.

Lewis's handbooks put a line's reach at about a quarter-inch of map (1976) and later at as much as 700 miles (1982, Cyclo*Carto*Graphy). Taking the 700-mile figure, Obama's zodiacal Pluto lines come near 766 cities in the site's list (33%). For Pluto, though, the method is the bigger uncertainty: at 45° S his in mundo rising line sits 1,406 km from the zodiacal one, wider than Lewis's whole 700-mile orb. The pre-filled map shows the zodiacal lines described here.