HOLLAND.FRIESLAND 30246] ’Van der Meulen astronomical clock in Franeker’.
’Van der Meulen astronomical clock in Franeker’.
The astronomical clock built by Cornelis van der Meulen between 1835 and 1842 is one of the exhibits in the Planetarium Museum of Eise Eisinga in Franeker.
Here we see a detail of its central dial plate. The outer (white) circle of the plate is inscribed with months and dates. An arrow moves along it (in a circular slit) pointing to the current date; in this case June 2nd (a small portion of the arrow is just visible near the top of the picture). The arrow also points to the position of the sun in the ecliptic, which can be read off from the second circle. The second circle is inscribed with the longitude degrees of the ecliptic coordinate system, with each zodiac sign taking up thirty degrees of the ecliptic circle (and zero degrees longitude placed at the beginning of Aries, on the right.) In this case the arrow points to the 10th degree of Gemini, which makes the longitude of the sun 70 degrees.
In the blue central part of the dial plate four dials can be seen that give information about the orbit of the moon. The “D” dial points to the longitude of the ‘Dalende Knoop’ (Descending Node) while the “K” dial points to the longitude of the ‘Klimmende Knoop’ (Ascending Node). These lunar nodes are the points where the orbit of the moon intersects with the ecliptic. When the moon passes through one of these nodes and happens to be full at the same time, there will be a lunar eclipse. And when it happens to be new there will be a solar eclipse somewhere on earth.
The “V” dial points to the longitude of the ‘Verste Punt’ (apogeum of the moon) while the “N” dial points to the longitude of the ‘Naaste Punt’ (perigeum of the moon). Photo Mick Palarczyk.