What this is
A sun position map, and the calculators around it
SunPosition.org shows where the sun and moon stand over any place on earth, at any moment you choose, drawn straight onto the map rather than listed in a table.
Drop the pin somewhere, scrub the timeline, and the day arc redraws: the sun's bearing and height, the length and direction of a shadow, sunrise and sunset with the twilight bands either side, moonrise and the moon's phase. Around that map sit the calculators that answer the same question from a different angle — the sun path for a latitude, shadow length from a height, the best tilt for a solar array, golden and blue hour, and sunrise, sunset and day length.
If you have not used it before, the guide walks through what every line and colour on the map means.
Who it is for
Anyone who needs to know where the light falls
- Photographers and film crews planning a shot for the hour the light is right, and checking which way a street faces before travelling to it.
- People buying or building — will the garden get afternoon sun in October, and how far away does that block of flats have to be before it stops mattering.
- Solar installers and owners sizing tilt, azimuth and the spacing between rows, and seeing what a tree or a chimney costs them across a year.
- Gardeners working out which corner of a plot gets six hours of sun and which gets two.
- Anyone curious about why the sun comes up where it does, and how far that moves between June and December.
How it works
Everything is worked out in your browser
There is no calculation server. The astronomy, the shading and the irradiation model all run as JavaScript on your own machine, which is why the timeline scrubs smoothly and why the site keeps working when the connection does not. The only things fetched while you use it are the map tiles from OpenStreetMap and, if you type a place name, a lookup through Nominatim.
Positions come from a standard solar series and a lunar series with the main periodic terms — good to roughly a hundredth of a degree for the sun and about a twentieth for the moon, which is far finer than the pin you drop on the map. The method page sets out the formulas, the definitions behind words like “sunrise”, the sky model behind the irradiation figures, and where each one stops being trustworthy.
Nothing about you is stored on a server, because there is no account and no analytics. What the site keeps lives in your own browser: the place you last looked at and your display preferences. The privacy page lists it item by item.
Being straight about it
What it does not do
Two things are worth knowing before you rely on a number here.
The horizon is flat. Sunrise and sunset are calculated against a level horizon at sea level. Behind a ridge or a mountain the sun really appears later and leaves earlier, sometimes by a great deal, and the site does not know your terrain.
Shading is what you tell it. The obstacle and the panels you put on the map are the only things casting a shadow. Real trees, fences, roof overhangs and next door's extension are not in the model unless you place them there yourself.
For planning, comparing and understanding, that is plenty. For a figure someone is going to sign a contract against — a bankable yield estimate, a legal right to light — treat this as the first look and have it checked against surveyed data.
Behind it
Who runs it, and how to get in touch
The site is published and maintained by the owner of the sunposition.org domain, referred to in the privacy policy and the terms of use as the Administrator. It is offered free of charge and paid for by advertising, which only loads if you agree to it.
Corrections are welcome, and so are the awkward ones — if a figure here disagrees with something you have measured, that is worth knowing. Write to contact@sunposition.org.
Map data © OpenStreetMap contributors, used under the Open Database Licence. Place search is provided by the OpenStreetMap Nominatim service.