NavList:

Many thanks Frank.I agree with all you say. The only reason I used Letcher, was it was the first I found that I could do with the Fuller slide rule. and yes, the Bygrave is just a hobby, but an intersting challenge for me with so little maths! (but I do get the RBA/Azdiff thing, I'm not quite that innumerate!)
Thanks for the summary of the "vertical circle" method of clearance.Awesome to my mind. Yes , I realsie it is not spherical trig or Bygrave territory! Very intersting. As you say, you could have saved the 18th century folk a lot of work!I could not find your original write up of this but will search the navlist files again.
On that historical note, I realise you have already got all that 18th century stuff(Tardis or not?). I'm just interested in the old Maskelyne methods and who did it prior to Green, Cook, almanac, and using the Mariner's guide.Certainly Purser Harrison (no relation) on Dolphin.I found some interesting discussions with the late G Huxtable on this in Navlist ? Did you/he ever do clearances using the Maskelyne Mariners Guide method? sorry if I missed the correct postings.
Many thanks again for all your help. (see previous post)and for humoring this rather obsolete , insane, sadly innumerate, but very enthusiastic celnav/Bygrave lunatic.
Best wishes
Francis
----------------------------------------------------------------
NavList message boards and member settings: www.fer3.com/NavList
Members may optionally receive posts by email.
To cancel email delivery, send a message to NoMail[at]fer3.com
----------------------------------------------------------------