⊗ Free Lot of Spirit Calculator: Day and Night Formula

Umbriel's free Lot of Spirit calculator finds your Part of Spirit from your birth date, time and place.

The Lot of Spirit, or Part of Spirit, is the companion to the Part of Fortune in the Hellenistic tradition. Where Fortune is built from the Moon and is read for the body and circumstance, Spirit is built from the Sun and is read for mind, will and what you deliberately do. It is a calculated point, not a body in the sky, measured from the Ascendant.

It flips by sect. For a day birth, the Sun above the horizon, the lot is Ascendant + Sun − Moon. For a night birth it reverses to Ascendant + Moon − Sun. That reversal is how the tradition defines it, and a calculator that applies the day formula to every chart puts a night birth's Spirit in the wrong place, often in a different sign and house. Umbriel checks whether the Sun was above or below the horizon and uses the right one, and it names the formula it used.

Because Spirit is Fortune with the Sun and the Moon swapped, the two always sit as mirror images across the horizon: the same distance from the Ascendant, one on each side. Add the two longitudes together and you get twice the Ascendant. That is a quick way to check any Spirit you are given against your Part of Fortune.

It is built from the Ascendant, so it needs an accurate birth time. Being arithmetic rather than a body, it has no orbit, no speed and no retrograde. It is a point the chart implies rather than something that was there in the sky.

This tool calculates the Lot of Spirit, a point on the zodiac found by arithmetic on three positions in your chart. Umbriel casts your natal chart, then takes the Ascendant and the longitudes of the Sun and Moon. For a day birth the Lot is the Ascendant plus the Sun minus the Moon; for a night birth the formula reverses to the Ascendant plus the Moon minus the Sun. Day or night is decided by whether the Sun is above the horizon, measured from the Sun's altitude at your place and moment and not read off the Sun's house, which is a different question in whole sign and several other house systems. The result is wrapped to 0 to 360 degrees, its sign is the longitude divided by 30 degrees, and its house comes from your cusps. Because the Part of Fortune uses the same three positions with the Sun and Moon swapped, the two always sum to twice the Ascendant. The formula needs the Ascendant and the sect, so it needs your birth time and place: on a chart with no birth time Umbriel calculates no Spirit at all. The Sun is checked against NASA/JPL Horizons to under 1 arcsecond over 1650 to 2050, the Moon to 0.27 arcminutes over 1600 to 2050, and the Ascendant to under 0.5 arcminutes, so the Lot is only as exact as those three added together. The Ascendant moves about a degree every four minutes on average, so a birth time out by a few minutes moves the Lot by about the same amount, and a time out by an hour can change its sign and house. What the Lot signifies is a symbolic tradition laid over a computed point.