Column sundial
The column sundial (also cylinder sundial ; Latin cylindrus horarius ) is an elevation sundial . It consists of a vertical cylinder with a shadow rod that can be rotated around its axis . This sundial was widely used in the late Middle Ages and early modern times . It was developed by Hermann von Reichenau (1013-1054). Shepherds used them in a smaller version, called the “shepherd's sundial” and made of simple materials - mostly wood or bone . When not in use, the shadow projector, a horizontally positioned rod, could usually be folded into the cylinder.
The date ( declination angle of the sun) must be known. You also have to know whether it is morning or afternoon. The shadow stick is placed over the valid date line. The clock is held with a vertical axis and with the shadow stick against the sun (stick shadow is vertical). The intersections of the date lines with the hour lines form a scale from which the morning or afternoon hour can be read. The display point is the end of the stick shadow.
The illustration shows a cylinder sundial for latitude 52 °. The dial also shows how the length of the day and the height of the sun ( elevation angle ) change over the course of a year.
literature
- Sundial Handbook , German Chronometry Society, Working Group Sundials, 2006, p. 73 and p. 128
- Fritz von Osterhausen: The great watch lexicon . Heel, Königswinter 2005, ISBN 3-89880-430-5
Web links
Individual evidence
- ↑ See Sonnenuhren-Handbuch , Arbeitskreis Sonnenuhren in the German Society for Chronometrie, 2006, page 128
- ↑ Dragon or shepherd sundial