Milky Way Calculator

The Milky Way season in Switzerland

The photogenic heart of the Milky Way – the galactic core in the constellation Sagittarius – is not visible all year. From November to January it is only above the horizon during the day: season closed. From February/March it appears in the early morning hours to the south-east, from May to July for most of the night to the south (peak season), and from August to October in the evening towards the south-west, setting a little earlier each week.

Three conditions must align

• Core above the horizon – from Switzerland the core never rises above about 14°. A clear view to the south is essential; even a moderate ridge can block it.
• Astronomical darkness – the sun must be more than 18° below the horizon. Around the summer solstice it is truly dark in Switzerland for only one to two hours.
• No interfering moon – even a half moon outshines the Milky Way. The ideal nights are around new moon – find them in the Moon Calendar.

On location

Light pollution is the fourth condition no calculator can handle: you need a dark location far from cities – in Switzerland for example at Tannensee on Melchsee-Frutt. The maximum exposure time for point-like stars is given by the 500 Rule Calculator, and what a night like that feels like is in my astrophotography blog post.

How is it calculated?

The position of the galactic core is calculated astronomically from its sky coordinates, sidereal time and your location; twilight and the moon's path use the same formulas as the golden hour calculator – all directly in the browser, without external services. "Interference-free" means the moon is below the horizon or below 25 % illumination. Not accounted for: weather, light pollution and the mountain silhouette on the horizon.