The Easter sky with its planets and constellations - Planetarium show
On 20 March is the beginning of spring, and on the Sunday after the spring full moon we celebrate Easter. But when the calendar became so inaccurate in the Middle Ages that no Lent was actually possible, Pope Gregory XIII had an observatory built in the Vatican. His astronomers succeeded in aligning the calendar with the position of the sun to the minute using a very simple method without telescopes, which had not yet been invented at the time. Thus, in October 1582, eleven days had to be skipped. Without the calendar reform, we would not celebrate Easter in 2022 until 28 April.
In the observatory there was nothing other than a pinhole camera (camera obscura), and I show with photos, taken at my home, that everyone has such a pinhole camera in the flat when the sun shines through shutter slits.