What is the formulat to compute King tracking rate for a given set of topocentric coordinates?
Too long for a comment. Possibly helpful resources:


http://www.bbastrodesigns.com/lib/
http://www.bbastrodesigns.com/lib/coordLib.js (file with actual formulas)
http://canburytech.net/DriftAlign/Equations.html
http://canburytech.net/GoQat/index.html (free software that implements this function)
"A manual of celestial photography: Principles and practice for those interested in photographing the heavens Hardcover – 1931" and it's 1988 reprint (ISBN 0933346468 for the latter, both available on Amazon), the original source.