Article of the month March

Planetary hours

This site offers, in Article of the month of December 2007, a short note concerning planetary hours.
The planetary hours referred to are based on the rise of 15° of the ecliptic and not on the diurnal arc of the sun.

In November and December 2008, Nicola Severino of Italy found important supplementary information on the subject in old literature.

Never before had we seen pictures featuring these planetary hours.
Thanks to the finds of Nicola Severino, this has now changed.

The first figure below shows a horizontal sundial with one hour line that satisfies the description given earlier.
It is indicated with a double line.
This hour line is the end of the sixth hour, when 90° of the ecliptic has risen.
The other curved hour lines in this figure do not correspond to planetary hours.

This image was found in a 1644 book in Latin by Ioanne Caramvel Lobkowitz ¹⁾.

The next figure shows an astrolabe tympanum with all 24 planetary hours: 12 day hours and 12 night hours.
This drawing comes from a German book from around 1508 - 1520 with a collection of images.
The author ²⁾ is unknown.

The third figure comes from a 1553 book by Oronce Finé ³⁾.
It also shows a tympanum, but here only half of each planetary hour is shown.
Oddly enough, the twelve day hours apply to the period of lengthening days, the twelve night hours to the period of shortening days.

More on this subject is found at or in:
Internet site of Nicola Severino (Italian)
NASS Compendium, March 2009 (English)
Bulletin of De Zonnewijzerkring, May 2009 (Dutch).