Hello Frank,
The URL below has a very good description of the effect you mention,
i.e., the offsets of the earliest/latest sunrise and sunset from the
solstices. The effect is a function of the EoT as well as latitude. For
Scotland then the fact that the length of day is changing faster than in
lower latitudes is the cause for the comparatively late sunrises. This
means as well that the offset mentioned earlier is not as noticeable.
http://da.saao.ac.za/sky/eqntime.html
Here is a URL to a Windows program that displays for a given location
both the length of day over the course of the year and the points of the
sunrise/sunset offset values. Except for having to enter your exact
lat/long every time you use it it's a very good tool.
http://www.analemma.com/Graphics/otherPhenomenon/SunGraph.zip
The Mac version of the program:
http://www.analemma.com/Graphics/otherPhenomenon/SunGraph.sit
Best,
Luke Coletti
Frank Evans wrote:
>
> Greetings fellow dialists,
> I came across this oddity in the (London) "Guardian" on Thursday 16 Nov.
> sent in by Hillary Shaw of the Geography Dept., Leeds University: I
> hadn't really registered that the equation of time could span half an
> hour over the year.
>
> The piece reads: In the last week of October, when the clocks go back,
> sunrise to sunset (London) is from about 6.45 to 1645 GMT, 10 hours of
> daylight. In spring we again have 10 hours of daylight around mid-
> February when sunrise to sunset is from 7.17 to 1715 GMT although the
> February day has a much later sunrise. December 21 may be the shortest
> day but the year's earliest sunset actually comes around December 12 and
> the latest sunrise is around December 30. It is darker mornings that
> affect the timing of the change between BST (DST) AND GMT.... So in
> October we keep BST till sunrise has reached as late as 7.45.... And we
> don't put the clocks forward in mid-February when again we have the same
> total daylight hours as in late October because sunrise would then be as
> late as 8.15 on the first morning of BST.
>
> (In Scotland, where the effects of BST on sunrise are even more
> pronounced in longer dark mornings there is substantial opposition to
> the added hour of BST. Perhaps we should return to sundial time.)
>
> Frank 55N 1W
> --
> Frank Evans
