My observing session

About this tool

This tool gives the three moments that frame a solar observing session at your location: sunrise, the meridian transit and sunset, in UTC, for any date. Rise and set are computed for the upper limb of the Sun touching the horizon, with the standard atmospheric refraction of 34′ — the usual convention of almanacs — from Explorer’s own implementation of the algorithms of Jean Meeus (Astronomical Algorithms, chapters 15 and 25).

The transit is the instant the Sun crosses your meridian and reaches its highest altitude, shown next to it — the moment its light crosses the least atmosphere. Times assume a flat horizon at sea level; hills, buildings or altitude shift the rise and set by a few minutes.

Near the poles the Sun may not rise or set at all on the chosen date; the tool then says so. Coordinates are entered in decimal degrees, latitude positive north and longitude positive east, and are only used to compute the page — nothing is stored. Never look at the Sun without a proper solar filter, whatever the time of day.