Alpenglow tells you when the light happens.

A ring of the day wraps the time and colours every phase by the brightness of the sky: astronomical night, twilight, blue hour, daytime, golden hour. A pip inside the ring marks the start of the next light window, and the watch can vibrate a configurable number of minutes before it opens.

A tap on the case opens Astro: sunrise and sunset, the next golden and blue hour with exact times, moonrise, moonset, and the moon phase drawn from its actual illumination rather than picked from stock pictures. Another tap opens a bulb timer for long exposures, reading to a tenth of a second, with an auto-stop so a forgotten measurement does not drain the battery.

Below the time: cloud cover, wind and visibility, coloured by how much they help or hinder a shot.

The phone does the computing - SunCalc for the astronomy, Open-Meteo for the weather. No account, no API key. Settings live on the phone.

Open source: github.com/Greenteyn/alpenglow-watchface