| ECLIPTIC DIAL - rotatable offset dial plate - offset is 23.5 degrees |
Illustrating Shadows the book, deliberately avoided the use of the ecliptic. It is not needed for most dial design, and although it is of
interest, the real isses for the diallist is the sun's declination.
Having said that, John Foad wrote a recent article on an ecliptic dial. This was well presented. To help better explain the ecliptic at the
solstices and equinoxes, and thus explain why the full moon rises in the north east in the winter, the southeast in the summer, I have
added some key pictorials, built with CAD.
This is a PDF file of around 550k, four pages, and has a very simple discussion on the ecliptic intersection with the earth and then
shows an ecliptic dial in use.
The dial shown here is a rotating gnomon dial for indicating the time, and a rotating 23.5 degree offset dial plate for calendar
information.
Updated - even better pictures, and assembly points to consider. Also monthly as well as seasonal
variations in the moon's apparent orbit in the sky. Also, the lunar dial supplement has been updated, and simplified
interest, the real isses for the diallist is the sun's declination.
Having said that, John Foad wrote a recent article on an ecliptic dial. This was well presented. To help better explain the ecliptic at the
solstices and equinoxes, and thus explain why the full moon rises in the north east in the winter, the southeast in the summer, I have
added some key pictorials, built with CAD.
This is a PDF file of around 550k, four pages, and has a very simple discussion on the ecliptic intersection with the earth and then
shows an ecliptic dial in use.
The dial shown here is a rotating gnomon dial for indicating the time, and a rotating 23.5 degree offset dial plate for calendar
information.
Updated - even better pictures, and assembly points to consider. Also monthly as well as seasonal
variations in the moon's apparent orbit in the sky. Also, the lunar dial supplement has been updated, and simplified
| ALSO vrml (about 100k) a user rotatable ecliptic model of the sun, earth at the solstices and equinoxes, with the ecliptic, see left. Needs the Cortona vrml browser plugin - see the vrml page here. ALSO vrml (about 300k) four armillary spheres set in the ecliptic plane to show their relationships, see below. |
