Astronomy Calculator for Windows
"Astronomical Algorithms" by Jean Meeus - Willmann Bell Publisher (very good)
"Astronomy on the Personal Computer" by O. Montenbruck & T. Pfleger - Verlag (very good)
"Astronomical Formulae for Calculators" 4thed - Jean Meeus - Willmann-Bell
"Fundamental Ephemeris Computations" by Paul J. Heafner - Willmann-Bell (very good)
"Math for Amateur Astronomers" by James H. Fox - Astronomical League (very good)
"Astronomy with your Personal Computer" by Peter Duffett-Smith - Cambridge University Press
"Spherical Astronomy" by Robin M. Green - Cambridge University Press
"Introduction to Basic Astronomy with a PC" by J.L. Lawrence - Willmann-Bell
"SunDials Their Theory and Construction" Alberrt Waugh - Dover
"SunDials Their Their Construction and Use" R.Newton Mayall & Margaret W. Mayall - Dover
"SunDials History, Theory and Practice" by Rene' R. J. Rohr - Dover (very good)
"Easy to Make Wooden Sundials" by Milton Stoneman - Dover
British Sundial Society
All great books on the subject matter.
Willmann-Bell and Dover are both great publishers for the Amateur Astronomer and Scientist.