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In my opinion the object shown in the image is
not a sundial, that is it doesn't serve to mark the hours. Moreover I don't believe that it is possible to
obtain the value of the azimuth of the wall only from this photo. The upper curve cannot be the hyperbola of the
winter solstice in a sundial facing East since it is too bent and it passes
almost exactly through the foot of
the orthostyle.
In a sundial facing East the foot of the
orthostyle passes through the
equinoctial line and the hyperbola
passes more high.
The curves that seem arcs of circle cannot be
compared to hour lines - that are practically rectilinear segments (in facing
East sundials). The lower curve looks like the summer solstice hyperbola in a East sundial , but it seems too far
from the orthostyles foot (for Latitude around 40° as
Probably the object is a game of shades that in
particular instants produce sketches , shapes and silhouettes . The fretworked plates (that can produce shades with particular
shape) are all orthogonal to the wall and placed vertically (their planes are vertical) and therefore
can be illuminated completely only
when the Sun is on the horizon and
their shadows become segments when the Sun is exactly in front of the
wall (thing that suggests a wall facing South) . Best Gianni Ferrari
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