On 09/02/2011 21:49, Donald Christensen wrote:
How do I design a longitude correction in my sundial?
Correct me if I'm wrong
My horizontal dial is for Brisbane. The longitude is 153 deg and the
standard meridian is 150. This is a 3 deg difference.
I'll then rotate the hour lines by 3 deg to compensate
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Cheers
Donald
0423 102 090
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So there!
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Hi Donald,
With any horizontal dial, if you are a whole number of
degrees to the East or West of your reference meridian, the gnomon
remains pointing true north and the hour/minute line divisions are
unchanged: you simply move the *numerals* around by the amount of the
longitudinal correction and choose the corresponding divisions to be
your hours, halves and quarters.
Myself I prefer the symmetry of an uncorrected layout with the
longitudinal correction incorporated in the Equation of Time table or
graph. In the latter case you simply move the graph plot up or down
from the zero line by the amount of the LC. This is also easier when
the LC isn't a whole number of degrees.
I'll leave you to work it out which way you have to move the numerals in
this case.
Hope this simplifies it.
Tony Moss
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