Cone sundial
display (outer digits): beginning of the eighth Babylonian hour, end of the 14th Italian hour
The cone sundial is a sundial with a cone as a shadow projector . It shows Babylonian and Italian hours and was first introduced in 1998 by the Spaniard Javier Moreno Bores .
The shadow-throwing cone has, as half the apex angle, the angle φ of the geographical latitude of the installation site. When designed as a floor sundial, the cone usually lies directly on the floor with a surface line and its axis is parallel to the earth. Its tip thus points to the south. Its right (looking north) shadow edge shows the time since sunrise (Babylonian hours), its left shadow edge shows the time since sunset (the previous day: Italian hours).
Like a pole rod, the sun is only depicted one-dimensionally . Instead of a single stick, an infinite number are effective throughout the day. The level of the Babylonian or Italian hours contains the sun regardless of the time of year ( declination angle of the sun) and touches the shadow-casting cone. With the daily rotation of this plane around the celestial axis (equal to the cone axis), the surface line tangent to the cone rotates, which thus continuously functions as a shadow-casting “rod”.
The hour lines on the floor scale are to be constructed similarly to those of a horizontal sundial . Their noon line is the line for sunrise (line “0”, Babylonian hours) or for sunset (line “24”, Italian hours). The second Babylonian hour is displayed on the 13 o'clock line and the 22nd Italian hour on the 11 o'clock line, because the shadow of the conical lines moves forward twice as fast as that of a pole.
literature
- Javier Moreno Bores: A New Family Of Sundials With Conical Gnomon The Compendium of the North American Sundial Society, Volume 5, Number 2, June 1998
Web links
- Frans Maes: UNofficial website of the Sundial Park in Genk (Belgium), 9th Conical Sundial
- Siegfried Wetzel: cone sundial
Individual evidence
- ↑ Javier Moreno Bores: A New Family Of Sundials With Conical Gnomon The Compendium of the North American Sundial Society, Volume 5, Number 2, June 1998