This type of sundial was developed or rediscovered in the 18th century. French watchmakers combined an analemmatic sundial (based on a date scale that shows the different positions of the sun throughout the year) with a conventional horizontal sundial. To use it, the vertical shadow pointer, also known as the gnomon, is set to the correct date and the clock is turned until both sundials show the same time. This means that it is correctly aligned without the need for a compass.
For all locations from Oslo to Cairo: The compass sundial from AstroMedia can be set to all latitudes between 26° and 65°. The double dial shows the time according to two different methods, which ultimately allows the compass direction to be determined. You can read both the true local time (solar time) and the "normal" time. The compass sundial aligns itself and can be set to all locations between Oslo and Cairo.
