Illuminate
illuminate.odd.place
Where on Earth the Sun is up right now, at any moment you choose, with sunrise, sunset and headings for any spot.
What’s going on How to use it Sharing Credits What’s going on
The bright side of the map is in daylight, the dark side in night. Between them run the twilight bands: civil twilight (the Sun up to 6° below the horizon, still light enough to read), nautical (to 12°, when sailors could still see the horizon to take star sightings) and astronomical (to 18°, after which the sky is fully dark).
For every point, the map works out how high the Sun is from the date and time: the Sun’s declination (how far north or south it is overhead, which makes the seasons) and the Earth’s rotation. Watch the shape of night change through the year: in June the Arctic never gets dark; in December the night side covers it completely.
The green circle
Drag it anywhere. Underneath the map you get that spot’s sunrise and sunset, the three twilights, solar noon, the Sun’s height and compass bearing right now, the Moon’s rise, set and phase, and the compass headings where the Sun and Moon rise and set. Every time is given on the green circle’s own local clock, in its time zone (shown above the times), wherever you happen to be.
Clear-sky UV index
Under the map, a chart shows the UV index the green circle’s spot would get through its local day under a cloudless sky, colored by the WHO scale (green low, yellow moderate, orange high, red very high, violet extreme), with the moment you’ve set marked in blue and a summary of the peak and when sun protection is advised (UV 3 or more).
It’s worked out from the Sun’s height using a standard approximation (UV ≈ 12.5 × the sine of the Sun’s altitude to the power 2.42, adjusted for ozone), typical ozone for the latitude and season, the Earth–Sun distance, and the ground’s height above sea level (about 7% more UV per kilometre). Real ozone varies day to day, clouds usually cut UV a lot, and snow, sand or water nearby add reflected UV. Treat it as a clear-day guide, not a forecast.
When the chosen date falls within about three months back to two weeks ahead, the chart adds a dark line : the hourly UV index with clouds, from Open-Meteo’s free weather model, and a grey strip along the top for cloud cover (darker is cloudier). For past days it’s the model’s record of that day’s clouds; for coming days it’s a forecast.
Sunlight on a square metre
Under the UV chart, a second chart and two tiles show how much sunlight a square metre at the green circle gets over its whole local day, midnight to midnight, under a perfectly clear sky. One square metre lies flat on the ground, so the low morning and evening Sun strikes it at a glancing angle and spreads out. The other sits on a mount that turns to face the Sun all day, the way a two-axis solar tracker does, so it catches the full beam from sunrise to sunset. The tracker’s advantage grows toward the poles in summer, when the Sun circles low around the sky for most of a very long day.
Two more square metres sit on fixed mounts. The first faces the equator (south in the northern hemisphere, north in the southern) at whatever tilt collects the most sunlight over the chosen day; the app tries every tilt and reports the winner. The best tilt swings through the year: steep in winter, when the Sun stays low, and shallow in summer. In the tropics in summer the best fixed position is often flat, because the Sun spends the mornings and evenings on the poleward side of the sky. The second is your mount : set the compass direction it faces and its tilt from flat with the two sliders, or press Set to today’s best fixed tilt to start from the best. Your mount’s settings are saved in share links.
Calculate the whole year adds up every day from 1 January to 31 December of the chosen year at the green circle, sampling the Sun every six minutes, and shows the year’s totals for all four square metres plus a month-by-month chart. For the year, the fixed mount is set once at the single tilt that collects the most over the whole year and never moved. Move your mount’s sliders afterwards and its yearly total updates at once. Moving the green circle or changing the year asks you to recalculate.
The same button also fetches a typical year of real weather : the hourly record of how much sunlight actually reached the ground at that spot over the last five complete years, clouds and haze included, split into the direct beam and the light scattered by sky and cloud. For each hour the app re-aims that beam at each square metre using where the Sun was, so cloudy mornings or stormy afternoons count against the mounts that face them. The best fixed position is then searched over every direction as well as every tilt, because where afternoons are usually cloudier (Florida’s summer storms, say) it pays to turn a little toward the morning Sun. Switch between Typical weather and Clear sky to compare, and the cloud chart shows how cloudy each hour of each month tends to be.
A day-by-day chart shows the year’s sunlight for each of the four square metres, one point per day. Move across it (or tap) to read any day’s totals. With typical weather the faint lines are each day of the five-year average, still ragged because even five years of weather is a small sample, and the bold lines are a 7-day running average.
Each total is given three ways: as energy (kilowatt-hours and megajoules per square metre, the units solar power uses), as visible-light photons (moles of photons between 400 and 700 nm, the “daily light integral” growers and coral keepers use; one mole is 6.02 × 10²³ photons) and as the total number of photons at all wavelengths.
The direct beam starts at 1361 W/m² above the atmosphere (about 3% more in early January, less in early July, with the Earth–Sun distance). It is dimmed by the thickness of air along the Sun’s path (the air mass), using Meinel and Meinel’s clear-sky formula with Laue’s correction for height above sea level. Light scattered from the blue sky adds about a tenth of the beam, and any tilted square metre sees the half of the sky it faces plus some light reflected off the ground (20%, typical of grass and soil). The photon counts use sunlight’s usual spectrum: about 2.05 µmol of visible photons and 4.3 × 10¹⁸ photons in all per joule. Real days are rarely this clear: haze and dust trim a few to twenty percent, and clouds much more.
Light pollution
Tick Light pollution to add the glow that city lights put into the night sky. It starts from NASA’s Black Marble map of Earth’s lights at night (VIIRS, 2016), treats each city’s light as shining upward, and spreads it across the surrounding few hundred kilometres the way scattered light fades with distance, following the approach of the World Atlas of Artificial Night Sky Brightness (Falchi and colleagues, 2016). It’s scaled so the brightest city centres get about 0.12 lux of sky glow, roughly a full Moon’s worth. The map shows it as an orange glow, and the light readings add it in.
It’s an estimate of sky glow under a clear sky, not of street lighting, which is far brighter but only right under the lamps. Clouds over a city make sky glow several times brighter, which this doesn’t model.
3D globe
Switch the view from Map to 3D globe and the same map, with all its layers, is wrapped around a sphere you can turn and zoom. It keeps updating as you play the clock or change anything. Drag to turn it, scroll or pinch to zoom, tap a spot to move the green circle there, and point at it to read the light anywhere.
The Moon picture
Beside the latitude and longitude, a small Moon shows its phase at the chosen moment: the lit part grows from the right as it waxes and shrinks to the left as it wanes, as seen from the northern hemisphere. Move the green circle south of the equator and it flips, as the real Moon does.
Moonlight
Tick Moonlight to add the Moon’s light to the map. Where the Moon is up at night, the darkness lifts and turns a cool blue-grey, by how bright the Moon is for its phase and how high it stands. A full Moon is roughly ten times brighter than a half Moon, and a thin crescent barely registers. Even a full Moon overhead gives about 0.25 lux, roughly a four-hundred-thousandth of noon sunlight, so the map shows it on the eye’s scale rather than the true one.
Under the map, and wherever you point at it, you’ll see the sunlight and moonlight reaching that spot in lux, for a clear sky, as if above the clouds. For reference: bright sun about 100,000 lux; an overcast day 1,000–10,000; sunset about 400; the end of civil twilight about 3; full moonlight 0.1–0.3; a moonless night about 0.001.
Overhead paths and directions
Sun and Moon overhead paths traces, for twelve hours either side of the chosen moment, the points on Earth where the Sun (solid yellow) and Moon (dashed blue) are straight overhead, with a dot where each is overhead right now. Each place sees the Sun at its highest as that path crosses its longitude at local noon. The Sun’s path sits at the latitude of the season (23.4° N at the June solstice); the Moon’s wanders further and shifts noticeably from day to day.
Rise and set directions draws lines from the green circle toward where the Sun and Moon rise and set that day, labeled with the compass bearing. Lines follow great circles, so on this flat map they curve.
How to use it
Move the green circle by dragging it, or type a latitude and longitude into the Lat and Lon boxes.Search for any place (a city, region or address) or type coordinates like 28.15, -82.75 or 28°9′N 82°45′W, and the green circle jumps there.Set a time on the green circle’s own clock (its time zone is shown) and press Update . Moving the circle keeps the same moment and shows it on the new place’s clock; Set to Local jumps back to now, where you are (your browser will ask for your location).Sunlight (on to start) shows or hides the Sun’s day, twilight and night shading. Shown as picks twilight bands (day, civil, nautical and astronomical twilight, night: the classic steps) or brightness (lux) : a smooth shading of how much light actually arrives, on a light meter’s log scale, with moonlight added in where it’s on. In brightness mode the low Sun near sunrise and sunset already shows dimmer, and full moonlight visibly lifts the night. Turn it off with Moonlight on to see the Moon’s light on its own: the whole map darkens and only the moonlit half glows, brightest beneath the Moon.Moonlight , Sun and Moon overhead paths and Rise and set directions turn the map layers on and off; all are saved in share links.Point at the map (or drag a finger across it) to read the sunlight and moonlight anywhere. Tap anywhere on the map to move the green circle there.⤢ Full screen gives the map the whole screen. On a phone the flat map fills the height and you swipe sideways to pan; − and + zoom in for detail. The 3D globe fills the screen too. ✕ Exit (or Esc) returns.Play runs the clock. The slider sets the speed, from a tenth of real time up to a million times faster, enough to sweep through a year in about half a minute.
Sharing
Press the share button (top right). It takes a picture of what's on screen and makes a link preview for it. Add a title if you like, then post it to Facebook, copy the link, or send it another way.
Clips: choose a shape (a 9:16 reel or a square) and a length, then Record a clip . The menu buttons hide while it films; press Stop to end early. You can keep playing with the controls while it records. The clip can go on your share page, be saved, or be posted as a Facebook reel.
Each share gets its own page with the picture, the clip if you made one, and a button that reopens this app with your exact settings.
Credits
Earth image: NASA Scientific Visualization Studio (Blue Marble, cloud-free).
Sun and Moon times: SunCalc by Vladimir Agafonkin.
3D globe: three.js .
Night lights: NASA Black Marble (VIIRS, 2016), via NASA GIBS. Sky-glow method after Falchi et al., “The new world atlas of artificial night sky brightness”, Science Advances (2016).
Place search: Open-Meteo geocoding (GeoNames data) and Nominatim , © OpenStreetMap contributors. Elevation, UV and cloud forecasts, and past sunlight and cloud records: Weather data by Open-Meteo.com (CC BY 4.0). Past records from the ERA5 reanalysis (Hersbach et al., 2020): contains modified Copernicus Climate Change Service information.
Time zones from a location: tz-lookup (public domain).
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