NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Tables of Trig Functions and Logs of Trig Functions
From: Gary LaPook
Date: 2007 May 02, 16:42 -0700
From: Gary LaPook
Date: 2007 May 02, 16:42 -0700
Gary LaPook wrote: I like to use my K&E slide rule sometimes for sight reduction just to stay in practice. Obviously it lacks the precision of a digital calculator but you do get useful answers. George Huxtable wrote: >Robert Eno wrote- > >| Essentially, for the same reason why I persist in using a sextant: the >| challenge of doing it the hard way. Oddly enough, I find it rather >| therapeutic to perform the odd sight reduction the old way using the trig >| and log tables. It also hones my basic understanding of the mathematics >| behind the calculations. It also gives me another level of independence of >| electronic gadgetry should the latter fail me absolutely some day. Don't >| misunderstand me: I still use a scientific calculator (and if I am >| particularly impatient, my Celesticomp V) but for every round of sights >that >| I take, I reduce at least one or two using the tables: the hard way. > >Comment from George- > >I agree with that, in every respect but one, where Robert writes "It also >hones my basic understanding of the mathematics behind the calculations." >And for this reason: because the basic simple spherical trig expressions >have been bent, twisted, and manipulated, quite beyond recognition, in order >to avoid additions and subtractions, once the navigator has "gone into >logs". This results in him going blindly through the set procedures "by >rote", without much chance of understanding the steps involved, and simply >accepting the result that comes out of that process. > >And so (in my view) doing all that trig manipulation by a pocket calculator >provides a breath of fresh air. Now that logs are no longer called for, the >basic trig expressions can be worked through, bit by bit, just as they come >out of the textbook. It's easy to see what contributions the individual >terms in the expressions are making. It's easy to try out simplifications >and short-cuts, such as taking the sine of an angle near 90 to be exactly 1; >that sort of thing, when you can see what you're actually doing. > >As I see it, having to use logs and lookup tables (and in their time, there >was really no alternative) set back the understanding of what navigators >were actually doing. Now we can enjoy the privilege of doing the >mathematical manipulations absolutely straight, and far more accurately than >we will ever need. How our navigational forbears, as recently as thirty-odd >years ago, would have relished that opportunity! > >George. > >contact George Huxtable at george@huxtable.u-net.com >or at +44 1865 820222 (from UK, 01865 820222) >or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. > > >> > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---