• Clear skies only: it opens on cloudless nights above freezing, and the info line (061 422 16 10) says from 6:30pm on Fridays whether it will
• Warm clothes and shoes, since the telescopes stand outdoors and in unheated rooms, and in the dark parents are responsible for their kids
• Sun viewing on first Sundays of the month in very good weather, an afternoon option for kids too young for a late night (none in July and August)

A public observatory run by volunteers of the Astronomischer Verein Basel. The 1928 dome houses a 20 cm Merz refractor, and three observation huts stand on the grounds. On public nights, kids look at the sky through the telescopes; on sunny afternoons, the Sun gets its turn through suitable instruments.

The grounds also hold MeteoSwiss weather stations, a seismograph, and the Basel climate record kept since 1755.