A watch for astronomers. Not sure whether I have a use for the complication (so what if there is a slight difference?) in my mundane day-to-day life. However, as a horologist, excellent piece of engineering!!
This watch houses two separate sub-dials for showing the mean solar and the sidereal time. This watch is powered by the all new A&S1311 calibre. You can see the sidereal time in the left sub-dial, and the mean solar time in the right sub-dial.
Solar time is measured by the apparent diurnal motion of the sun, and local noon in apparent solar time is the moment when the sun is exactly due south or north (depending on the observer’s latitude and the season).
Sidereal time is a “time scale that is based on the Earth’s rate of rotation measured relative to the fixed stars.
A mean sidereal day is about 23 hours, 56 minutes, 4.0916 seconds (23.9344699 hours or 0.99726958 mean solar days),