A transit is the position of a planet in the sky right now, compared with the positions fixed in your birth chart. A transit chart lays today's sky over the chart you were born with, and astrologers read the angles between the two to describe the kind of period you are in. It is the main method behind serious yearly forecasts — and the reason those forecasts describe types of periods rather than dated events.
The birth chart never changes: it is the sky at one moment, fixed for life. Everything that *does* change in astrology comes from comparing that fixed picture with the moving one. That comparison is what a transit is.
Most searches for the word come down to the same two questions — what is a transit, and how do I read a transit chart — with a third close behind: *how much should I trust it*. All three deserve a straight answer.
Take one point in your birth chart — your natal Sun, say, at 14 degrees of Taurus. Now look at where Saturn is today. If Saturn is also at 14 degrees of Taurus, it is conjunct your Sun by transit. If it is at 14 degrees of Leo, ninety degrees away, it is square your Sun. The transit is simply the current planet, the natal point, and the angle between them.
Astrologers use a short list of angles, called aspects: the conjunction (0°), the opposition (180°), the square (90°), the trine (120°) and the sextile (60°), each with a few degrees of tolerance either side, called the orb. A transit is *in orb* while the moving planet stays within that tolerance, and *exact* at the moment the angle is precise.
That is the whole mechanism. Everything else — which transits matter, how long they last, what they are read to mean — follows from which planet is moving and which natal point it touches.
The planets move at wildly different speeds, and the speed decides how long a transit stays in orb. A fast planet passes a natal point in hours or days and is read as the weather of the week. A slow one sits on the same degree for months, goes backwards over it, and returns — and those are the transits that describe whole chapters.
A transit chart is usually drawn as a bi-wheel: the birth chart on the inner ring, the current sky on the outer, so that any transiting planet can be seen against the natal one it is touching. Three things are read from it, in this order.
Which natal point is being touched. A transit to the Sun, the Moon, the ascendant or the Midheaven is felt across the whole life; a transit to a planet is felt in that planet's area. A transit that touches nothing within orb is, for practical purposes, not happening.
Which planet is doing the touching. Saturn on the natal Moon and Jupiter on the natal Moon are the same natal point with opposite weather — the first asks for discipline and patience with feeling, the second for generosity and room. The transiting planet sets the tone.
Which house it is moving through. Slow planets spend years in a house, and the house says where in life the period is playing out — work, home, partnership, money. This is the part that needs a birth time: the houses come from the ascendant, and without a time the house of a transit is a guess.
A transit describes the type of period: whether the coming months lean towards building or dismantling, whether they ask for patience or reward initiative, and which area of life the pressure or the opening is in. Read well, that is genuinely useful — it is the difference between fighting a Saturn period and using it.
What a transit cannot do is name an event. Saturn square the natal Sun does not mean a redundancy, a break-up or an illness; it means a stretch of months in which the person's standing and vitality are tested and have to be earned rather than assumed. How that shows up depends on the life it lands in. Any reading that says *on this date this will happen* has left the chart behind.
The other honest limit is direction. A transit can say the period is heavy; it cannot say whether the person comes out of it stronger or worn down. That part is not in the sky.
Three tools for reading time get confused with one another. Transits are the moving picture — the planets against the natal chart, day by day, the method that gives *when* within a year. A solar return is a single snapshot taken once a year, when the Sun returns to its natal degree, and is read for the overall emphasis of the year. A Saturn return is one particular transit — Saturn back on its own natal degree — that comes round once in about twenty-nine years.
Used together they are complementary: the return for the shape of the year, the transits for the timing inside it, and the Saturn return, when one falls, as the thing that colours everything else.
A transit is measured against the natal chart, so the natal chart has to be right first — and for houses and angles, that means a real birth time rather than a rounded one. A transit chart built on a natal chart drawn for noon will place the ascendant, the Midheaven and every house in the wrong sign about nine times out of ten, and every transit to those points with them.
Start with the fixed half of the picture. You can calculate your birth chart here for free: every planet by sign, degree and house, the ascendant and Midheaven, and the chart wheel — the ring that any transit chart is drawn around. The calculation runs in your own browser.
A transit is the current position of a planet compared with a point in your birth chart. When the moving planet forms one of the standard angles — conjunction, square, opposition, trine or sextile — with a natal planet or angle, it is said to be transiting that point. The birth chart never changes; transits are how astrology describes what is changing.
It depends entirely on the speed of the transiting planet. Moon transits last hours; Sun, Mercury and Venus transits a few days; Mars a week or two; Jupiter weeks to months; Saturn months, often returning three times over a year as it turns retrograde and forward again; Uranus, Neptune and Pluto one to two years. The slow transits are the ones that describe whole chapters of a life.
They describe the type of period, not the event. A hard Saturn transit describes months in which something has to be earned rather than assumed; it does not say that a specific thing happens on a specific date, and it does not say how the person comes through it. Any forecast that hands you dated events has stopped reading the chart.
For transits to the planets, no — the date and city fix the planets well enough. For transits to the ascendant, the Midheaven and the houses, yes: those come from the birth time, and a chart drawn for noon puts them in the wrong sign about nine times out of ten. Without a time, read transits to planets and leave the houses open.