About

About this notebook

Noon Marks is a notebook about sundials: how they work, how to lay them out, and why they disagree with the clock.

The notes are written for people who want to build a dial rather than buy one, so they keep the arithmetic and leave out most of the history. Where a result has a well-known name or story attached, it is mentioned so it can be looked up.

Every diagram is drawn by a short script for latitude 51.5° N, which runs through London. Change that one number and every angle on the site changes with it.

Corrections are welcome in the old-fashioned way: by noticing that a dial disagrees with the notes and working out which of the two is wrong.