Thanks for the mental exercise, Frank. I think that Willy might squeeze another 15 seconds of illumination at the end of December owing to the rapid change in the EoT. A useful graph showing the rate of change of EoT is provided by the USNO at:
http://aa.usno.navy.mil/faq/docs/eqtime.php Geoff Thurston On 14 June 2016 at 13:01, Willy Leenders <[email protected]> wrote: > > See on my website: http://www.wijzerweb.be/analemmatischengels.html > The maximum time (12 hours) of sunlight on a vertical wall of any > direction is above the Arctic Circle on a day when the midnight sun shines > > Willy Leenders > Hasselt in Flanders (Belgium) > > Visit my website about the sundials in the province of Limburg (Flanders) > with a section 'worth knowing about sundials' (mostly in Dutch): > http://www.wijzerweb.be > > > Op 14-jun-2016, om 10:29 heeft Frank King het volgende geschreven: > > Dear Dan, > > The approach that you describe does > indeed show you how long the sun can > theoretically shine on a vertical > wall, for a given solar declination, > provided (as you say) that you know > the times the sun rises and sets. > > Now a simple exercise... > > What is the maximum amount of time > the sun can shine on a vertical wall? > > You can choose the latitude and you > can choose the orientation of the > wall and you can choose the solar > declination. > > Frank King > Cambridge, U.K. > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > >
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