The brass disk on the movable part represents the
Sun. Sliding it up and down along the month scale, between the limits, allows
the device to be set for any time of year.
To use the Solar Motion Model, pivot the
compass disk in the north/south direction so that it moves along the scale that
is labeled “Latitude”. Align it with the latitude of your location (or one you
may be interested in). The compass disk will be perpendicular to the frame, and
you are visualized to be at the center of this disk. Next, slide the “Sun” along
the outer rim of the frame to the appropriate month. The edge of the compass
disk represents the visible horizon for some imaginary person standing in the
center of the disk.
To see the path the Sun makes across the sky
for that particular latitude and time of year, swing the month portion of the
frame completely from the “East” to the “West” as shown on the compass disk.
Compare the location of the sunrise and sunset at different times of the year.
How does the length of day change with the
seasons? At what latitude must you be so the Sun does not set on the longest day
of the year? What would it be like to live at the north pole? You can answer
these and many other questions with your Solar Motion Model!