From a city name to a map of the sky

Anyone can draw a circle with twelve sectors. The hard part is the planets being where they actually were, and that is where most personalised posters sold online fail silently: nobody looks at a birth chart and notices the ascendant is an hour out.

So we publish the method. Not to boast about precision, but because a gift you cannot verify is decoration.

You type "Bilbao" and we need a point on the surface of the Earth. The name is resolved to real latitude and longitude before anything is computed. If geocoding fails, the order stops: we would rather not sell you a chart than sell you one in the wrong place.

This is where most of them fall over. The time on a birth certificate is local time, and local time in Madrid in 1978 is not local time in 2026: offsets change, daylight-saving rules change, and some countries have moved zone entirely.

We resolve the IANA time zone in force at that exact point on that exact date, and convert to universal time with it. An hour of error moves the ascendant about fifteen degrees. That is not a nuance, it is a different chart.

With the instant in universal time, planetary positions are computed. It is the most mechanical part of the process and the one that varies least between serious providers.

Placidus, Whole Sign, Koch and the rest divide the twelve houses differently over the same planetary positions. None of them is the correct one: they are conventions, and different astrologers work with different ones.

What is not acceptable is failing to say which was used. Yours is written down with your order, together with the zodiac (tropical or sidereal), so whoever reads the chart knows which convention they are looking at.

Every order carries a PDF with the resolved coordinates, the time zone, the house system and the zodiac. We do not copy it from what we drew: the certificate resolves the coordinates again, with the same function the graphics engine used.

That sounds excessive and it is deliberate. A certificate that merely repeated what the drawing says would prove nothing except that we can copy a number.

You can still order. Without a time the planetary positions remain correct; what stops being reliable are the houses and the ascendant, and that is flagged. You see the preview before paying and decide with the piece in front of you.