The Sundial of Belogradchik [In Bulgarian]

A method of measuring the average sun time with a cylindrical sundial is presented in this article. The innovation represents the use of a gnomon–memory system, which has a numerical register consisting of information about the time addition necessary for the average sun time to be determined. This information can be found on the register using a moving, opaque, output point (a top of a pointer) and its shadow. This new idea is in a process in realization in Belogradchik.