Dan, Using a watch seems too imprecise to give more than a general idea of the direction of North. However, the basic concept has been developed to provide precision solar compass instruments. In most cases these come with tables to correct latitude, date and local solar time. If you don't know it, you might enjoy a glance at Malcolm Barnfield's article *The Sundial goes to War * http://www.sundials.co.za/THE%20SUNDIAL%20GOES%20TO%20WAR%20web.pdf
Best wishes, Patrick Vyvyan On Mon, 22 Oct 2018 at 14:09, [email protected] < [email protected]> wrote: > dear Dan > > the wristwatch as compass has 3 problems: > a) it shows the time of a different longitude, the one of the time-zone > (GMT or DST). > You should correct it for the local time but it is possible only if you > know your longitude. > > b) you should correct the time also for eot, it means you should start > with the local Sun time for the longitude where you'll use it. > > You can admit a little bit of imprecision avoiding a) and b), if your > longitude is not so far from the one of the time-zone. > > c) you have to rotate the watch around the 3-9 axes of the colatitude > angle, so you have to evaulate also your latitude. > > Overall it isn't a reliable way to find the north, it is useful to have > a rough estimate if you haven't other instruments. > > I have some 3D drawings for a book I'm writing, I attach 2 images, if > you wish I can send you, or anyone who request them, a more defined jpg. > > ciao Fabio > > -- > > Fabio Savian > [email protected] > www.nonvedolora.eu > Paderno Dugnano, Milano, Italy > 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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