March 2016
Page 9

Reader's Letter

This letter addresses the move to abolish leap seconds, which are introduced to keep UTC (GMT) linked to to mean solar time. The author argues that abolition would cause accurately constructed fixed sundials, such as the Dolphin Dial at Greenwich, to become increasingly inaccurate over decades. Happily the 2015 World Radiocommunication Conference postponed any decision until 2023.

Martin Hogbin

June 2013
Page 18

A Garden Heliochronometer (A Mean-Time Horizontal Dial)

A personal account of designing and constructing a mean-time garden sundial capable of reading clock time directly. The author explains the concept, geometry, and testing of his heliochronometer.
DIY Sundial Projects, Dials: Heliochronometer, Dials: Horizontal, Mathematics of Dialling

Martin Hogbin