What Transits Are

Once a day this app works out that day's positions and compares them with the positions at your moment of birth, looking for the angles taught earlier. Any it finds are listed, naming which body has reached which of your placements. With a birth time, transits to the Ascendant and houses are added too.

So a transit is the result of comparing two sets of degrees. Today's sky is the same for everyone. What differs is your own table from the moment you were born — which is why the same day touches different placements for different people.

To read a transit, look at three things: which body is moving, which of your placements it touches, and what angle it makes. Take “transiting Mars square your Sun”: Mars is moving, your Sun is touched, and the angle is a square.

A common reading is that the moving body brings the theme of that stretch of time, and the placement it touches is the part of you that gets stirred. So the same transiting body reads differently on your Sun than on your Moon.

How to compare: write down what those days were actually like, then look back after a while to see which descriptions fit and which did not. Bit by bit you learn which transits show most clearly in you.

What the old texts say: Ptolemy deals with “when” in Tetrabiblos Book IV ch. 10, “Of the Division of Times.” It divides a life into stages by rule, and says general conditions (such as country of birth) come before particular details: first the wider setting, then the personal details.

For transits the orbs are tighter than for a birth chart: 1 degree in general, 2 for the Sun and Moon, and “exact” means within 0.1 of a degree. The reason is simple: a transit is about “now,” and an 8-degree orb would keep one angle going for weeks, which is no longer now.

Slow bodies — Jupiter, Saturn and the outer planets — stay a while even inside a 1-degree orb, while the Moon is gone in a day. So the difference between “these few days” and “these few years” mostly comes from which body is moving.