Short answer: a birth chart poster is accurate when it is calculated from three things: your exact birth date, your birth time, and the coordinates of your birthplace, with the historical time zone of that place applied. Natal Atelier calculates every chart this way, so the planet positions on the poster match the sky at your moment of birth to a fraction of a degree. The part that depends most on you is the birth time: the more exact it is, the more of the chart can be shown.
What "accurate" means for a birth chart
A birth chart (natal chart) is a diagram of where the Sun, the Moon and the planets were along the zodiac at a given minute, seen from a given place on Earth. It is an astronomical calculation first. An accurate chart gets four things right:
- Planet positions — each planet's exact degree within its zodiac sign.
- The Rising sign (Ascendant) — the sign on the eastern horizon at that minute.
- The houses — the twelve divisions of the wheel, which start from the Ascendant.
- The aspects — the angles between planets, drawn as lines across the centre.
How a Natal Atelier chart is calculated
- Your birthplace becomes coordinates. You choose your city from a list, so we use its latitude and longitude rather than guessing from a name.
- Your local time becomes universal time. We apply the historical time zone and daylight saving rules for that place on that date. This step matters more than most people expect: time zone rules have changed many times in many countries.
- The planets are placed with an astronomical ephemeris. Positions are computed for that exact moment. In our checks against reference charts, planet positions agree to within about 0.005°.
- Houses are drawn with the Placidus system, the most widely used house system in Western astrology. For births above about 66° latitude, where Placidus cannot be calculated reliably, we use whole-sign houses instead.
- Your Sun, Moon and Rising signs are printed under your name, taken directly from the calculated chart.
You can see the result before you buy: enter your details on the product page and a preview of your own chart appears in seconds.
Which details matter most
| Detail | What it affects | How sensitive it is |
|---|---|---|
| Birth date | Sun sign and the slow planets | The Sun changes sign about once a month |
| Birth time | Rising sign, houses, the Moon's exact degree | The Rising sign changes on average every two hours; the Moon changes sign about every two and a half days |
| Birthplace | Rising sign and houses | A different city at the same moment can shift the Ascendant by several degrees |
What if I don't know my birth time?
You can still order. Without a time, we cannot calculate the Rising sign or the houses, so we leave them out and show the Sun, the Moon and every planet in their signs. The Moon is placed at its noon position for your birth date. That is correct for most people, but if the Moon changed sign that day it may fall in the neighbouring sign. Your poster says "Birth time unknown" so it is always honest about what it shows.
Good places to find a birth time: a birth certificate, a hospital record, a baby book, or a parent.
Frequently asked questions
Is a birth chart poster the same as a star map?
No. A star map shows the constellations visible overhead from a place on a date. A birth chart places the Sun, Moon and planets around the twelve zodiac signs for an exact minute and place. See Birth Chart vs Star Map for a side-by-side comparison.
Why does my Rising sign differ from a free app?
Usually because of the birth time, the birthplace coordinates, or the time zone used. Check that the time is in local time for the place you were born and that the right city is selected.
Can I check my chart before ordering?
Yes. The live preview on the product page uses the same calculation as the printed poster.
Astrology is offered for entertainment and reflection only. It does not predict events and is not advice of any kind.