How to Find Out-of-Bounds Planets in Your Birth Chart

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To find out-of-bounds planets, you need each planet's declination for your exact birth moment and the Sun's limit for that date. The method takes four steps:

1. Look up the declination of each body for your birth date, time and place.
2. Find the limit for that date: the true obliquity of the ecliptic, close to 23°26′ for modern charts.
3. Compare the size of each declination with the limit, ignoring north or south. Greater than the limit means out of bounds.
4. If a value is very close to the limit, call it borderline and check it again.

What out of bounds means, which planets can do it and how often, is on out-of-bounds planets.

Calculator note: the free birth chart does not calculate or display declination, and it has no out-of-bounds flag or setting, so you will need another source for step 1. The worked figures on this page were calculated offline for this article, as educational arithmetic, using the same position routines the free chart uses (see the methodology page). Ask the Astrologist is not given your planets' degrees or declinations and cannot work out whether a planet is out of bounds. If you look the declinations up, you can share them there.

Step 1: get the declinations

Use a reputable ephemeris or chart service that lists geocentric declination for each planet. Enter the same birth date, time, place and time zone you use on the free chart. A one-hour time error, such as a missed daylight-saving change, can materially shift the Moon's position, which matters when its declination is close to the limit, so get the clock right first; birth time, time zones and daylight saving covers the traps.

Check what the column is:

• Declination is usually labelled Decl., Dec or δ, with N or S, or + and −. That is the one you want.
• Latitude (Lat.) is measured from the ecliptic, not the equator. It is a different number, usually small, and it is not used for this test.
• Longitude is the sign and degree, such as 4°25′ Capricorn. Declination cannot be read off it.

Geocentric means measured from Earth's centre, the convention used on these pages. A service that gives topocentric values, from the birth place, can show the Moon up to about a degree different.

Step 2: find the limit for the date

The limit is the largest declination the Sun can reach in that epoch: the true obliquity of the ecliptic on the birth date. It changes slowly. Between 1920 and 2059 it stayed between 23°25′47″ and 23°27′03″.

• If your source prints the obliquity (often labelled ε or Obliquity), use that value.
• If it does not, 23°26′ is a reasonable first screen for a modern chart, but only a rough one. If a declination is close enough to it that the exact value for the date could change the answer, check it against the true obliquity for that date.
• 23°27′ is a familiar rounded value from older references. It is not the limit used here, and near the line it gives a different answer.

Step 3: compare

Take each declination, drop the north or south, and compare the number with the limit:

• Greater than the limit: out of bounds. Note whether it is north or south.
• Equal to or less than the limit: in bounds. Equality is not out of bounds.

The difference between the two is the margin. Writing it down tells you whether the result is clear or close.

Step 4: borderline values

There is no agreed tolerance, and this site does not set one. If the classification is close enough that the exact true-obliquity value, the source model or rounding could change it, report it as borderline, show the actual margin and name the convention. Lotte's chart below is a worked example. Three things can flip a borderline result between sources:

• the limit: true obliquity of the date, mean obliquity, or a fixed 23°26′ or 23°27′;
• the source model: different ephemerides can differ by fractions of an arc-second to several arc-seconds;
• rounding: a source that shows whole arc-minutes cannot settle a margin of seconds.

A different answer from another source in that zone is usually a convention or rounding difference, not proof that either source is wrong.

Worked example: Ruben's ten bodies

Ruben is the fictional example chart used across this site: London, 5 January 1993, 12:00 GMT (12:00 UT). The limit for that date, the true obliquity, was 23°26′23″.

Two planets are out of bounds, Mercury and Mars, and both margins are large, so the result does not depend on the convention. The 23°26′ screen and the 23°27′ figure give the same answer here. An independent check with the Swiss Ephemeris agreed to within about half an arc-second for every body.

Four bodies are in Capricorn, the Sun, Mercury, Uranus and Neptune, and their margins run from 51′ beyond the limit to nearly 2° inside. Sign alone does not tell you.

Worked example: a borderline case (Lotte)

Lotte is another fictional example chart used on this site: Utrecht, 27 August 1991, 06:55 CEST (04:55 UT). Her Uranus, at 10°03′ Capricorn, is the only body near the line; every other body is more than 1½° inside.

On the convention used here, Lotte's Uranus is in bounds, but only by 8 arc-seconds, so the right description is borderline. An independent Swiss Ephemeris check gave the same declination and limit to within a fraction of an arc-second, still about 8″ inside. A chart service that uses a fixed 23°26′ would list it as out of bounds. Neither source has made a mistake; they use different limits. Uranus was moving further south at the time and crossed the limit about two days later, which is why a margin this small changes so quickly.

Without a birth time

Declination changes through the day, most of all for the Moon. Without a birth time you cannot assume one: do not use noon, or any single moment, as if it were the birth time. Check the whole local birth date instead.

1. First screen: look up the declinations at 00:00 and at 23:59 local time on the birth date.
2. If the two disagree for a body, its status depends on the birth time. Report it as unknown.
3. If they agree, that is encouraging but not proof. Check several times in between, every few hours, especially if a value is near the limit.

How much this matters was measured on 13,311 local dates from 1920 to 2059, each checked 25 times (every hour from 00:00 to 23:00 local time, plus 23:59, Amsterdam clock):

The Moon needs the most care. On 4 in 10 of the dates when it was out of bounds at some check, it was in bounds at another, and on one date the 00:00 and 23:59 checks agreed while the status changed in between. Without a birth time, treat a Moon out-of-bounds label as uncertain unless the whole date is checked. Moon sign without a birth time covers the same problem for the Moon's sign.

Mercury, Venus, Mars and Pluto were usually stable through a date in this check, but not always. Even Jupiter and Uranus changed status during a date a handful of times, so the whole-date check is worth doing for every body.

Ruben's date shows what a stable result looks like: across all 25 checks on 5 January 1993 in London, Mercury and Mars stayed out of bounds (at least 49′ and 2°36′ beyond the limit at every check) and the Moon stayed in bounds (at least 20′ inside). For the general picture of what a chart can show without a time, see birth chart without a birth time, and for how precise a time needs to be, how accurate your birth time needs to be.

Common mistakes

• Reading latitude as declination. They are different coordinates; only declination counts here.
• Reading the sign degree. 4°25′ Capricorn says nothing on its own about declination.
• Using 23°27′ as an exact limit. It is a rounded older value. Use the true obliquity for the date.
• Calling an arc-second margin a firm result. Report it as borderline.
• Using a noon chart for an unknown birth time. Check the whole local date.
• Treating out of bounds as a sign or house change. The planet keeps its sign, house, aspects and retrograde status.
• Expecting the free chart to show it. It does not calculate declination.

This page covers the Sun, Moon and planets from Mercury to Pluto. Chiron, Black Moon Lilith, the Lunar Nodes and the chart angles are not part of this method; the out-of-bounds planets page explains why.

Next steps

Once you know which planets are out of bounds, out-of-bounds planets explains how some astrologers read them as a modifier, and why a slow planet out of bounds is shared by a whole cohort. To talk it through, give the declinations you found to Ask the Astrologist, or explore more guides in the Planets library.

Related articles

• Out-of-Bounds Planets: When a Planet Goes Beyond the Sun's Limits
• How Accurate Does Your Birth Time Need to Be?
• Don't Know Your Birth Time? What Your Chart Can Still Show
• Moon Sign Without a Birth Time
• Moon Square the Lunar Nodes
• How to Find Angular Planets in Your Birth Chart

See how this plays out in your own chart →