NavList:

Thanks Ken,

that is even more amazing! Human computers did what must have been thousands of lunar clearance calculations, old style to get that?

Presumably, Margett "simply" chose a limited number of results from the tables  and made  fair curves through those data points to obtain the intermediate results by visual interpolation? Either way, what an immense achievement for the 1770s!

Any idea if these tables are available digitally on line? I've had a quick look on the Cambridge libraray web site but could not find one.

Also, you mentioned back in 2006 some of your test results. Have you done any since? If the graphs are based on 1772, Lyon/Shephard tables, then do you or maybe Frank know how accurate they were then compared to more recent tables? Presumably the maths of clearance was correct then even if there were some inaccuracies of final result due to errors of actual lunar postions etc which were improved over subsequent years?

Thanks again. 

Francis