Transit chart and transit lines

What a transit chart shows

A transit is a moving planet making an aspect to a planet or angle of your birth chart. The transit chart puts the two together: your birth chart in the inner ring and the planets of the date you choose in the outer ring. Astrologers read transits as the timing layer of astrology: the birth chart describes the themes of a life, and transits describe when each theme is in focus.

The table lists every transit within the orb you choose, closest first, whether it is still building (applying) or fading (separating), and every date it is exact. A slow planet that turns retrograde can cross the same point three times over several months, and each crossing is listed.

How to read the transits

• Slow planets set the chapters. Transits of Saturn, Uranus, Neptune and Pluto last months, and astrologers read them as the major turns of a life. Jupiter's last weeks to months.
• Fast planets set the days. The Sun, Mercury, Venus and Mars cross each point in days and are read as short triggers, often timing the slow transits.
• The aspect gives the tone. A conjunction joins two planets' themes, a trine or sextile is read as easy flow, a square or opposition as tension that asks for action.
• The house gives the stage. The table shows the house of your birth chart each moving planet is passing through: the area of life where its theme plays out.

Transit lines on the map

Your transit lines bring the transits onto the world map. A transit line marks where a planet of the chosen date sits on an angle of your relocated birth chart: on the Ascendant (AC line), Descendant (DC), Midheaven (MC) or IC. The method was developed by Jim Lewis, the astrologer who popularized astrocartography, who called it cyclocartography.

Lines of slow planets barely move for months, so they show where a long transit is felt most strongly: the places where transiting Jupiter or Saturn sits on your angles this year. The table under the map names the biggest city near the MC and AC line of each one. To follow the lines day by day on the 3D globe, open them in the Today tab of the live map, where you can step through the days or pick any date.

Transit lines are different from the live sky lines of a date, which show where each planet is rising or overhead in the real sky at that minute, for everyone.

How it is calculated

Positions come from the same planetary engine as the rest of the site, tested against NASA JPL Horizons (see method and accuracy). Exact dates are found by searching the planet's path around the chosen date: a few weeks for the Sun, up to about 400 days either way for the slow planets. Transit lines take each planet's position on the chosen date and place it with the sidereal time of your birth, the frame of your relocated birth chart, drawn in the sky like the main map. Everything runs in your browser.