Fascinating stuff, thanks for the info! -- Jan
On Tue, Mar 22, 2011 at 09:09, Willy Leenders <[email protected]> wrote: > Marcelo, > 1. > The littele moon in the clock shows the moon's phases and in what sign the > moon is. > See an animation at: > http://www.praguealacarte.com/orloj/orlojLoader.html > 2. > The winter signs are narrower in length, not in angle. > And the angular velocity of the hand through the sign is constant. > The explanation is: > The little sun is always located on the edge of the zodical ring. > In summer the little sun must follow the outer ring of the clock, in winter > the inner ring of the clock > Therefore the zodical ring is rotating around his own center and around the > center of the clock. > His position is always eccentric in the clock. > See on my website at page http://www.wijzerweb.be/prague.html > Click at the bottom of the page to open the Excel worksheet. > By changing the data in the yellow cels the clock will appear in any > position and all will become clear. > Willy Leenders > Hasselt in Flanders (Belgium) > Visit my website about the sundials in the province of Limburg (Flanders) > with a section 'worth knowing about sundials' (mostly in > Dutch): http://www.wijzerweb.be > > > > > > > Op 22-mrt-2011, om 14:45 heeft Marcelo het volgende geschreven: > > How is that lunar dial? Does it show the moon's phases and in what sign it > is? > And I'm intrigued by that zodiac, why are the winter signs (Sagittarius, > Capricorn, Aquarius) narrower than the summer signs, Gemini and Cancer? > > 2011/3/22 Willy Leenders <[email protected]> >> >> More than the clock in Prague the clock in Bern has a calendar dial built >> in and an indication of the day of the week. >> The calendar in Prague is located separately under the clock. >> >> See http://upload.wikimedia.org/wikipedia/commons/5/5e/Zytglogge_astronomical_clock_with_labels.png >> >> Willy Leenders >> Hasselt in Flanders (Belgium) >> Visit my website about the sundials in the province of Limburg (Flanders) >> with a section 'worth knowing about sundials' (mostly in >> Dutch): http://www.wijzerweb.be >> >> >> >> >> >> >> Op 22-mrt-2011, om 11:26 heeft Willy Leenders het volgende geschreven: >> >> Jan, >> A better photo of the clock in Bern is >> at http://www.photographersdirect.com/buyers/stockphoto.asp?imageid=1511348 >> This clock has at first sight a similar design as the clock in Prague. >> However, it has not a outer ring that moves to and fro to indicate Italian >> or Bohemian hours. >> An indication of sidereal time is also missing. >> Willy Leenders >> Hasselt in Flanders (Belgium) >> Visit my website about the sundials in the province of Limburg (Flanders) >> with a section 'worth knowing about sundials' (mostly in >> Dutch): http://www.wijzerweb.be >> >> >> >> >> >> >> Op 22-mrt-2011, om 01:02 heeft Jan Bielawski het volgende geschreven: >> >> Is the Prague clock of the same design as the one in Bern? See e.g. >> http://starswebworx.lc-stars.com/swiss_photo/Bern.htm (scroll down a >> bit). >> >> -- >> Jan >> >> On Mon, Feb 28, 2011 at 09:15, James E. Morrison >> <[email protected]> wrote: >> >> Perhaps some background would be useful to those on the list who are not >> >> familiar with astrolabes and astrolabe clocks. >> >> The Prague clock is based on an astrolabe with the projection origin at >> the >> >> north celestial pole. This orientation causes the horizon arc to arc in >> the >> >> reverse direction from a normal astrolabe, but it gives a more intuitive >> >> representation of the Sun's position. >> >> The clock has three moving parts. A hand with a Sun figure rotates once >> in >> >> a mean solar day and the Sun's longitude is indicated by the position of >> the >> >> Sun figure on the ecliptic (which is divided by the zodiac). The >> astrolabe >> >> rete, which has only the projection of the ecliptic on the clock, rotates >> >> once in a sidereal day. The difference in the rate of the two components >> >> keeps the Sun figure on the (approximately) correct position on the >> >> ecliptic. The third hand shows the position and phase of the Moon. >> >> The Prague clock, and all other devices based on the astrolabe, indicates >> >> apparent time with the Sun hand. The only adjustment needed for it to >> >> indicate approximate civil time would be to simply move the Sun hand to a >> >> time. No changes in gearing are needed. But the Sun's position in the >> >> ecliptic (zodiac) would no longer be correct and any events (sunrise/set, >> >> culmination, etc.) would no longer be valid. That is, the Sun figure no >> >> longer represents the real Sun, >> >> It could be made to show apparent time again by simply moving the Sun >> hand. >> >> Best regards, >> >> Jim >> >> James E. Morrison >> >> [email protected] >> >> Astrolabe web site at http://astrolabes.org >> >> --------------------------------------------------- >> >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
