You never cease to amaze me; you seem to know about everything.
I have one cautionary note, however. Many planetary position routines were
designed with modern astronomers in mind. They don't always go back to
ancient and medieval times with the kind of precision you want. The ideal
kind of review of these programs would test their planetary and lunar positions
for periods up to 2500 years back against Tuckerman's tables (which go back
to 601 BC) and if you really want overkill -- against the Jet Propulsion
Even here, there are problems, as there are small discrepancies (up to
several hours) on the accepted values of the rotation of the earth so we
aren't quite sure how long ago 2500 Julian years (2500 x 365.25 = 913125 days)
is in the atomic time that governs such physical processes as the motion of the
moon and planets. It does get messy. A tip, if any of the programs are based
on the parameters of two French dynamical astronomers, Simon and Bretagnon,
they should be very good (ceteris paribus).
One last point, I'm not as happy as you with Duffett-Smith's _Practical
Astronomy with Your Calculator_. It's nice as an easy introduction to the
principles, but there are far too many oversimplifications for serious
historical work. In particular, he treats the planetary periods as constant,
which gets increasingly inaccurate beyond 1900, and worse by the medieval
period. For more detail see my review in _Journal for the History
of Astronomy_, 13(1982):218-220. I've heard he has a more recent book
on _Practical Astronomy with your Computer_ in which he may have paid more
attention to historical detail. Nonetheless, since the _Planets_ program
is based on Duffett-Smith, I'm suspicious of it as well.
By the way, what does this have to do with medieval texts?