Capuchin Dial

This instrument is a portable sundial for a single latitude, developed by Regiomontanus (1436-1476). It also indicates the time of sunrise and sunset.
It is equipped with a simple Sun sight on the upper edge. A thread with a sliding bead is hanging from a movable point of suspension within the date scale.

See instructions for interactive use below

Gunter's quadrant

Quadratum Horarium Generale (Regiomontanus Dial)

Apian Dial

Visit my Applet Collection

Details for interactive use:

Enter the year into text field,
and hit the button "Apply input".
(Gregorian Calendar only, later than 1582)
Enter the latitude (decimal degrees) into the text field,
and hit the button "Apply input".
The latitude is indicated in the text field.

The interactive regions (light gray scales) are changing the cursor to cross hair.
elevation angle
                altitude Sun
Click into the degree scale (light gray) on the lower and left limb to direct the quadrant to the Sun. The thread will follow the elevation angle.

Use the "Today" button to set the thread to the current date. The bead is set to the noon point automatically.

- Click into the light gray calendar (date scale,  upper part for winter and spring, or lower part for summer and autumn) to set the thread to the date.

- To bead is set to the noon point automatically.

                sunrise sunset
Read the date, the declination, and the time of sunrise and sunset (neglecting refraction on the horizon), the equation of time, the current time, and elevation as computed by astronomical algorithms.

Select from the "Display Options" menu.
The red frame of the applet area is a square (753 x 753 pix, same size as for the Quadratum Horarium Generale and for Gunter's quadrant).

The dial is obeying the equation of the nautic spherical triangle (h = elevation angle, φ = latitude, AH = hour angle):
sin h = sin φ sin δ + cos φ cos δ cos AH

Under construction!

Rohr, René R. J.: Die Sonnenuhr. Geschichte, Theorie, Funktion.
Callwey, München 1982.

Meyer, Jörg: Die Sonnenuhr und ihre Theorie.
Harry Deutsch, Frankfurt 2008.
Web Links

Regiomontanus, Apian and Capuchin Sundials

Johannes Regiomontanus: Calendar

Das Allgemeine Uhrentäfelchen von Regiomontan

Tragbare Sonnenuhren in Europa ab 1400

Uhrentäfelchen von P. Aegid Everard

Pourquoi le cadran de Regiompntanus fonctionne-t-il ?

Horoscopion Apiani Generale Dignoscendis Horis cuiuscumque generis aptissimum

Quadratum Horarium Generale Georgius Hartman

Quadratum horarium generale (1496)

Regiomontanus (Wikipedia)

Regiomontanus (Mac Tutor)

© 2009-2023 J. Giesen

Last modified: 2023, Oct 07