LunaSun, moon and rising: the big three, and why they are three
Most people meet a chart through three answers, and those answers come off three different clocks. That is the whole reason a calculator asks for three things.
| Sign | Driven by | Moves | Needs |
|---|---|---|---|
| Sun sign | the day of the year | one sign a month | the date |
| Moon sign | the Moon’s own orbit | one sign every 2 days 6 hours | date, and usually the time |
| Rising sign | the Earth turning under you | a whole circle in a day | date, exact time, city |
The rising sign is the strict one: it moves about a degree every four minutes, so it is the part of a chart a rough time damages first. It has its own worked section - rising sign, with the minutes each sign holds the horizon.
Free birth chart: what free means here, and what it does not
Nothing on this site asks for an email, a card or an account to run a calculation. The calculators sit one click away, on the pages where the answer belongs: sun sign, moon sign, rising sign, the ten planets, the twelve houses and the aspects between them. This page is the reading, not the form - worth saying plainly, because plenty of “free birth chart” pages are a sign-up wall with an article in front of it.
What costs money anywhere is never the arithmetic. Ephemerides are published; the sums take milliseconds. What people pay for is somebody turning 40-odd positions into a paragraph they can use.
Why Cafe Astrology, Astro-Seek and Co–Star hand you three different charts
Same birth data, three sites, three answers - and none of them is broken. Four settings differ, and each one moves a specific thing.
| Setting | What it moves | By how much |
|---|---|---|
| Zodiac: tropical or sidereal | every sign in the chart | 24°13′ in 2026 - four fifths of a sign |
| House system: Placidus, Koch, whole sign… | which house a planet falls in | one or two houses (three above 50°N); something moves in 97% of charts |
| Lunar node: true or mean | the node’s degree | up to 1.95° apart, 1950–2010 |
| Historical time zone | the whole chart, through UTC | an hour, sometimes two |
Our calculators use tropical signs, Placidus houses and the true node, and they resolve the time zone from the coordinates of the town for the year you were born rather than from today’s map. That last one quietly rescues a lot of wartime and Soviet-era birthdays, where the clock on the wall was not the clock the atlas remembers.
Kundali, rashi, vedic chart: why your sign changes when you switch
Western astrology measures from the spring equinox; Indian astrology measures from the fixed stars. The two zeroes drifted apart over two thousand years, and the gap has a name and a number: the ayanamsa, 24°13′ at the start of 2026 on the Lahiri standard.
Subtract that from a western position and most people slide back one sign. Counted day by day across 1960–2030, the vedic Sun sign differs from the western one on 79.3% of birth dates - roughly four people in five. Nobody made an error; the two systems answer from different starting lines. Our pages are tropical, and say so.
What a birth chart is made of
| Element | What it is | What it speaks about |
|---|---|---|
| Sun | the sign the Sun stood in | the core, what a person moves towards |
| Moon | the sign of the Moon | feelings, what is needed to feel safe |
| Rising sign | the sign coming up on the horizon | how a person comes across |
| Mercury, Venus, Mars | personal planets | thinking, love and taste, will and anger |
| Jupiter, Saturn | social planets | growth and support, maturity and limits |
| Uranus, Neptune, Pluto | outer planets | generational themes, deep change |
| Houses (1–12) | sectors of the chart | the area of life where it all plays out |
| Aspects | angles between planets | how the parts of a character get along |
I don’t know my birth time: what that actually costs
Here is the price, measured rather than guessed. Four thousand charts were cast twice on the same New York coordinates, the second time with the birth moment nudged, and the pairs compared.
| Birth time off by | A planet moves house | The rising sign changes |
|---|---|---|
| 10 minutes | 63% | 8% |
| 30 minutes | 97% | 25% |
| 1 hour | 100% | 50% |
| 4 hours | 100% | 100% |
Read the right-hand column as reassurance rather than alarm: “about half past two” keeps the rising sign right nineteen times in twenty. The houses are the fragile part, which is exactly why a certificate is worth digging out. And a chart with no time at all still hands you nine planets in signs and every aspect between them.
How the chart is actually calculated
Positions do not come from a table someone typed up. They come from ephemerides - published astronomical data on where each body is. The professional standard is the Swiss Ephemeris, and that is what runs under our pages.
The order of work: date and time go to UTC through the time zone that place used in that era; longitudes come out of the ephemerides; the coordinates of the town give the ascendant, the MC and the twelve cusps, on the Placidus system. An aspect counts when the angle is inside the orb - 6° for conjunction, square, trine and opposition, 8° once the Sun or Moon is involved, 5° for a sextile.
Example: 17 May 1993, Moscow, 12:00
Sun at 26°25′ Taurus, Moon at 8°14′ Aries, rising sign 22°02′ Leo. Those figures match a public calculator down to the arc second, and that precision is the point: houses and aspects hang off the exact degree, not off “roughly Taurus”. Read it the other way and it also tells you the date: 3°35′ of Taurus were left, the Sun covers about a degree a day, so this birth fell four days short of Gemini. Dates that actually land on a changeover happen on 3.3% of birthdays - about one in thirty.
Frequently asked questions
Birth chart or natal chart - is there a difference?
None. They are two names for one drawing: the sky at your moment of birth. “Birth chart” is the commoner phrase in everyday English, “natal chart” the commoner one in astrological writing, and “astrology chart” turns up in search about as often as both. This site uses them interchangeably on purpose.
Can a birth chart be built without a birth time?
Yes, and it is worth having. Planets in signs are still exact; houses and the rising sign are not, because they depend on the Earth turning. The one soft spot is the Moon: it changes sign on 43.9% of dates, so on those days a time is needed to settle it.
Where do I find my exact birth time?
Usually the birth certificate, the hospital record, or whoever was in the room. If all you have is “sometime in the evening”, enter the middle of that window rather than nothing - an approximate time beats no time by a wide margin.
Sun, moon or rising - which one is really me?
All three, doing different jobs. The Sun is the direction you keep coming back to, the Moon is what you need in order to feel steady, the rising sign is the first ninety seconds a stranger gets. People who say a chart “does not fit” are usually reading one of the three and expecting the other two.
How many aspects does a normal chart have?
About 15 of the 45 possible pairs, with most charts landing between 11 and 19. A chart with a lot of them is busy, not doomed, and a quiet one is not empty - it simply says its piece through fewer connections.
Is astrology a science?
The arithmetic is astronomy and it is exact. The reading is not: it is a symbolic language for thinking about yourself, not a method of prediction. If you want the numeric cousin that needs only a date, that is the destiny matrix - a separate system, so the two cannot contradict each other.
The content is for entertainment and self-reflection. It is not a substitute for medical, legal or financial advice.
Build your own chart
Luna runs exactly the arithmetic this page describes - Swiss Ephemeris, Placidus houses, the orbs listed above - and then says the result out loud: Sun, Moon, rising sign and the two or three tightest angles, in the words you would use with a friend.
Open Luna