Two-wire Dial

Invented in 1922 by the German mathematician Hugo Michnik, the two-wire dial has the effect of indicating the hour by the intersection of the shade of two wire crossed, perpendiculars between them and parallel with the plan of the dial.

The two wire are not with the same height. The wire highest, height $h_1$ , is parallel to the local Méridien. If the height $h_2$ of the wire low is such as $h_2=h_1 \ sin \ phi$ ( $\ phi$ represents the Latitude), then one can have a constant angle of $15^o$ between the time lines, provided that their intersection is placed at a distance $a=h_2/\ tan \ phi=h_1 \ cos \ phi$ of orthogonal projection on the table of the intersection of wire.

Reference

H. Michnik, <>, Astronomishe Nachrichten, 217 (5190), p.81-90, 1923

See too

Sundial

External bonds

http://www.nonvedolora.it/english/bifilare_en.htm (in English)

Site of Dominique Hake, http://membres.lycos.fr/gnomonic/lagnomonique.html (articles very detailed on various types of two-wire dials)
another Web site of this author, http://cadsol.ifrance.com/index.php (complete articles on the two-wire ones, addresses associations of gnomonic in the world, bibliography on gnomonic the two-wire etc…)

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