What we show
The sun and moon data appears in several places on the site:
- On each individual catch — a panel under the catch details showing the day's sun and moon curves for the exact place and time, plus the moon phase within the cycle the catch was made in.
- At /moon — the main page, with today's chart, the coming full and new moons, and a short history of the solunar theory.
- At /moon/today — today's sun and moon chart for Sweden as a whole.
- At /moon/upcoming — full and new moons 12 months ahead.
- By date — every day has a page of its own (for instance */moon/2026/06/15*) with that day's sky chart.
- By county — each of Sweden's 21 counties has its own *today* page, computed for the centre of the county.
- On the water pages — lake, river and sea pages carry a *Sky and moon* panel computed for the water's own coordinates.
How it is computed
Everything astronomical is computed locally. Nothing is fetched from an outside service, nothing has a rate limit, and nothing costs anything to ask for.
Three sources drive the calculations:
- The moon phase — the synodic month (29.53 days) applied to the time of the catch.
- The position of the sun — NOAA's standard solar position algorithm, exact for a given latitude and longitude.
- The position of the moon — Jean Meeus, *Astronomical Algorithms*, chapter 47, the standard reference for lunar position.
Because everything is computed locally, the same data works as well for a catch you log today as for a historical date decades back. The water's exact coordinates are used, so sunrise and sunset times are right for the actual place rather than for the geographical centre of Sweden.
The solunar theory — a short background
The idea that the positions of the moon and sun affect the activity of fish is usually credited to the American fishing writer John Alden Knight, who published his solunar tables in the American sporting press in the 1920s and 1930s. Knight argued that fish feed most actively during four short periods a day — when the moon passes directly overhead or directly underfoot, and at moonrise, moonset, sunrise and sunset.
The idea has survived in tables, almanacs and apps for close to a century. The empirical support is mixed: some studies have found correlations, others have not. We present the positions of the moon and sun as they were; whether they matter for your fishing is for you to judge from your own log.
What you can do with the data
The data is there to help you read your own catches, and perhaps to find patterns in your own log.
- On the catch page you can see exactly what the sun and moon were doing when you caught the fish. Over time that builds up a picture of the conditions you actually fish in.
- At /account/statistics there is a summary of your own catches spread across moon phases and sun positions. It is your own data, for you alone — nothing is compared with anyone else.
- Before a planned trip you can look at /moon/today, or at a particular water's *Sky and moon* panel, to see how the light will fall over the day.