What is a transit?

Your birth chart is a single moment held still: the arrangement of the sky at the time and place you were born. It does not change. A transit is what happens when the sky keeps moving and the planets, as they travel now, form angles with the fixed points of that birth chart.

That is the whole idea. The natal chart is the instrument and the transits are the music played across it. When a reading speaks about "this month," it is reading transits: where Venus or Saturn or the Moon travels during that month, and what it touches in the chart you were born with.

The two charts in every transit

Every transit has two parts, and it helps to keep them apart in your mind.

The first is a moving planet, somewhere in the sky during the period being read. The second is a fixed point in your birth chart. That point can be one of your natal planets, one of the angles such as the Ascendant or Midheaven, or a sensitive point such as the Nodes. A transit is described by naming both and the angle between them: transiting Saturn square your natal Sun, transiting Venus trine your natal Moon.

A moving planet also passes through your houses. When Jupiter travels through your fifth house, it is not touching any one planet, but it is lighting up the room of pleasure, romance and creativity for as long as it stays there. So a reading tracks two kinds of transit at once, contacts to planets and passages through houses. The houses depend on your birth time, which is one reason a reading asks for it; without a time, a reading can still follow the contacts to your planets but cannot say which room is being visited. The primer on the twelve houses explains what each room covers.

Why a reading is built on them

A Sun-sign horoscope speaks to a twelfth of the world at once. A transit-based reading does not. It looks at where a moving planet falls against your particular placements, so the same week in the sky lands differently for two people born a day apart, and very differently for two people born in different years.

Take a simple example. Suppose Mars is travelling through Capricorn. For someone whose Sun is in Capricorn, Mars eventually reaches the Sun and forms a conjunction, and the weeks may feel driven, impatient and full of energy for their own aims. For someone with the Moon in Cancer, the same Mars sits opposite, and those weeks may bring friction at home or with family. For someone with nothing near those points, the passage may barely register. Same sky, three different months.

This is what lets a reading be written for one reader and not for a category. The natal chart sets who you are; the transits set what the season is asking of you now.

Fast movers and slow movers

Not all transits move at the same pace, and the pace is most of the meaning.

The Moon is the quickest. It circles the whole zodiac in about four weeks and changes sign every two or three days, so it governs mood and the small weather of a week, not the shape of a year. Lunar transits pass too quickly to carry a big story on their own, but they often mark the day a longer theme becomes noticeable.

The Sun, Mercury, Venus and Mars move at a more human speed. The Sun takes a year to go round, so it crosses each of your placements once a year; its return to your natal Sun is your birthday. Mercury and Venus stay close to the Sun and move at a similar overall pace, though their retrogrades make them linger. Mars takes about two years to circle the chart. These transits tend to mark the chapters of a season: a few weeks of heavier correspondence, a warmer stretch in love, a burst of effort at work.

The slow movers are the ones that change a life. Jupiter takes about a year in a sign and twelve years to go round. Saturn spends around two and a half years in a sign and returns to its birth position close to the age of twenty-nine, which is the Saturn return. Uranus, Neptune and Pluto move so slowly that a single transit to one of your planets can stay active for a year or two. When a reading describes something foundational, such as a long restructuring or a slow opening, it is usually one of these at work.

Returns and the long cycles of a life

Some of the most useful transits are the ones where a planet comes back to where it started, or reaches the far side of its circle.

A return happens when a moving planet arrives at its own natal position. The Sun's return comes every year on or near your birthday, and many astrologers read a chart for that moment as a picture of the year ahead. Jupiter returns roughly every twelve years, around the ages of twelve, twenty-four, thirty-six and so on, and those years often bring a widening: a move, a course of study, a new kind of confidence. Saturn returns near twenty-nine and again near fifty-eight, and those passages are famous for asking what is truly yours to build.

Halfway round, a planet opposes its own birth position. Saturn's opposition in the mid-forties and Uranus's opposition in the early forties together account for much of what people call a midlife reckoning: a period of questioning structures that once felt settled, and a wish for more freedom inside them.

These cycles are shared by everyone born in the same few years, so they describe stages of life more than personal events. What makes them personal is the house each planet is passing through and the other placements it touches along the way.

The angle decides the tone

A transit's character comes from three things together: the moving planet, the point it touches and the angle between them. The planets supply the subject; the angle supplies the tone.

A conjunction, where the moving planet reaches the same place as your natal point, concentrates and begins things. A trine or sextile tends to flow, making the matter easier or opening a door you still have to walk through. A square creates pressure and usually asks for a decision or an adjustment. An opposition brings the matter into view through other people, so it is often felt in relationships. The primer on aspects goes through each angle in more depth.

No angle is simply good or bad. A Saturn square can be the hard, clarifying push that finally ends a job you had outgrown. A Jupiter trine can be so easy that you let it pass without doing anything. Readings describe the quality of the pressure and what it asks for; what you make of it is yours.

Windows, not moments

A transit is not a light switch. It does not begin the instant a planet reaches an exact angle and end the instant it passes.

Astrologers use the word orb for the window of influence around the exact point: the approach, the peak and the wane. A transit can be felt as it draws close, sharpens when it is exact and lingers as it separates. Fast planets move through that window in a day or two; slow ones can take months.

The slow planets add a further pattern. From Earth, every planet except the Sun and Moon appears to stop and move backward at intervals, which is called retrograde motion. So an outer planet can reach one of your points, turn retrograde and pass back over it, then turn direct and cross a third time. That is why some themes arrive, recede and return across a year before they settle. The first pass often raises the question, the second revisits it and the third tends to bring a resolution.

So when a reading marks a particular week, read it as the centre of a window, not a single dated event. The sky rarely keeps appointments to the hour.

What transits do not do

A few misunderstandings are worth clearing away.

Transits do not make things happen to you as if you had no part in it. They describe the pressure and opportunity of a period, and the same transit can show up as a quarrel for one person and an honest conversation for another. They also do not override the birth chart. A transit can only activate what is already there, so a heavy transit to a placement that is well supported in your chart may feel far lighter than it sounds.

Nor are all transits equally important. Most months contain dozens of small contacts, and a careful reading ranks them, giving the most space to slow planets and to contacts with the Sun, Moon, the chart ruler and the angles. A long list of every aspect is data; a reading is the choice of what matters.

Reading your own transits

To read transits at all you need two things: your birth chart, cast from your date, place and ideally your time, and the positions of the planets for the period in question. The first comes from a free birth chart. The second is the astronomy of the moving sky, calculated for the dates being read.

What a personal monthly reading adds is the interpretation: which of the month's contacts land on your chart, which rooms they pass through, and what that season is asking of you. It is simply the practice of naming the tone for the chart that is yours, one month at a time.