You may not want to draw hour-lines on a pillar dial that have the
Equation of Time and longitude corrections built in, but rather figure
these corrections yourself after taking a reading.  The reason is that
all such dials I have seen use the same lines for morning and afternoon
hours.  You can do this if you have symmetry about the 12:00 line.

However, the shadow progresses in opposite directions (down and up) along the
shared hour-lines in the morning and afternoon.  Therefore, if you have an added
or subtracted offset such as you apply from the above two corrections, it has
the effect of splitting the lines between morning and afternoon lines.  You then
have more lines to display, and it may be difficult to distinguish between them.
Of course, if you have a large pillar dial (as you might be planning), this will
be less problematic.

Ron Doerfler


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