Hello Fer,
Yes I understand, and with my SunClock I indeed use the center of the
projected solar disk to bisect the Analemma(and IMHO, with great
precision and accuracy) BUT it is my understanding that craftsmen of the
past made use of the fact that the contrast of a cast shadow can be best
resolved if one "offsets" the hour lines one would normally draw by the
semi diameter of the sun i.e., line up the hour line with the limb not
the center. This was meant, I assume, to improve its precision/accuracy.
Charles, in his e-mail, brings up Chinese shadow sharpening techniques,
this is exactly the direction I was hoping this thread would take, not
about "enforcing" paradigms.
Best Regards,
Luke
fer j. de vries wrote:
>
> Luke Coletti wrote:
> >
> > Hello Roger,
> >
> > Any thoughts on how one should calculate solar coordinates to be
> > most
> > precise/accurate? Most solar coordinates are computed for the center of
> > the solar disk, I would like to hear feedback (since I don't believe
> > this topic has come up yet) on using coordinates based of the solar limb
> > (instead of the center) to increase both precession and accuracy of the
> > cast shadow. I await another stimulating thread.
> >
> > Best Regards,
> >
> > Luke
> >
>
> Luke,
>
> If you use a rod as shadow caster or a hole in a disk to produce a spot
> of light to read a sundial you have to calculate the coordinates of the
> center of the sun. We than read the time at the center of the shadowline
> or at the center of the light spot.
>
> If you use an edge of a solid body then perhaps you may use the
> coordinates of the limb of the sun.
>
> But please, have in mind we are dealing with sundials, not with
> instruments to read a time in parts of a second or minute.
>
> Don't forget the history of sundials. How did people the things at their
> time?
> In our time we have other instruments to measure time as precisely and
> accurate as we want.
> A sundial still has to reflect to the older times and a suntime hour is
> irregular in length.
> Even then I can construct precise and accurate dials.
>
> Happy dialling, Fer.
>
> --
> Fer J. de Vries
> [EMAIL PROTECTED]
> http://www.iaehv.nl/users/ferdv/
> lat. 51:30 N long. 5:30 E
