To
Download:
The program needs Win95/98/NT..., Vista.. It's language is English or German and
can be fixed in the program's menu. Since version 1.5 the format of
help-files is *.chm which is also compatible with Vista (and Wiindows 7?).
Program "Alemma.exe" calculates different types of
analemmatic sundials . Common analemamtic sundials register local time but
not mean time. The "Split analemmatic sundial" which is
calculated in this program too, allows reading mean time with very good
approximation. Both, dial plane and shadow casting gnomon, may be
inclined. But calculations are restricted to gnomons which lie within the
meridional plane. The dial plane may be inclined but, must not show any
deviation to west or east.
Following types of analemmatic sundials are calculated:
1. "Classical" analemmatic sundials with linear date scale
along the minor axis (North-South-axis) :
Analemmatic sundials consist of a movable gnomon. The marks of all hour
points are on an ellipse. If a person or a gnomon is positioned on the
actual date mark of the analemmatic sundial then, the shadow line points
to local apparent time. The marks of the hour points can be shifted
along the ellipse in that way, that apparent time of the zone meridian
instead of local apparent time is registered. So longitude correction
can be done.
2. Analemmatic sundials with one single 8-slope as date line:
Under some specific conditions a sundial with a single 8-slope as date
line can register exact mean time at noon. Then the 8-slope is a
mirrored Analemma containing EoT (We define the Equation of Time EoT as:
EoT = local apparent time - local mean time) .
3. "Split" analemmatic sundials :
Split analemmatic sundials consist of to halves of an ellipse and of
two separated analemmas (8-slopes), one for the morning hours and one
for afternoon. Calculations show, that standing on the date point of
such an 8-slope allows reading mean time all through the day with very
good approximation, and this even for the whole year. Fred Sawyer
further showed how to calculate 8-slopes, which register exact mean time
(or Standard time) for two particular times before noon and for two
particular times in the afternoon. Because there exist many different
methods to calculate the "best-fitting" analemma points, 4
different methods are offered.
The time marks show time intervals of 60 min, 30 min, 20 min, 15 min, 12 min or 10 min. Further 1, 2, 3 or 6 date marks per month are drawn along the date line. All results are displayed on screen graphically and in tables. Additionally all can be printed on any printer installed in Windows.
Since version 1.3 constructions can be saved as dxf- or hpgl-files, since
vers. 1.4 the tables of ALEMMA can be saved in Excel format *.csv. The
construction can be saved in dxf-format and hpgl-format.