Thomas Mudge 1765 By about 1750, precision regulators were relatively common. Here, the dial has 2 minute hands. The gilded hand shows true solar time -- the time indicated by the apparent passage of the sun in the sky, as shown by a sundial. The blued-steel hands show mean solar time, or clock time, which is constant. The disc in the arch shows the daily difference between the two, called the equation of time.
aperture=f2.8 focal length: 60.0 mm exposure 1/100 sec ISO: 3200