A55 - today a real express way !

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fras
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Joined: Tue Apr 10, 2012 18:34

A55 - today a real express way !

Post by fras »

Had a tootle out today in the MB SLK, (it needs a run now and again as it's a diesel).
Went to Rhyll and used the A55, and it was all clear with little traffic, yet this was a Saturday ! Clearly the month of the year has a huge influence !!. OK, I know you all know this anyway, but it meant our ride was enjoyable, rather than tedious. On the other roads, the storm had knocked down a lot of trees, so one had to drive cautiously at all times.
On the way back I noticed how the twilight last so long at this time of year. Why is this, anybody know ?
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Was92now625
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Location: near A625

Re: A55 - today a real express way !

Post by Was92now625 »

fras wrote: Sat Nov 27, 2021 17:50 On the way back I noticed how the twilight last so long at this time of year. Why is this, anybody know ?
Twilight is longest close to the solstices (June (especially - by quite a margin) and December) and shortest around early March and October. Full answer requires spherical trig but in the summer after the sun sets it is moving "under" the pole rather than straight down. Something similar in December.

At this time of year, probably a clear horizon will have more to do with it.
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wrinkly
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Re: A55 - today a real express way !

Post by wrinkly »

The first PDF link on this page shows duration of twilight against date for a range of north (upper graph of each pair) and south (lower graph of each pair) latitudes. Rhyl and the A55 are about 53 deg N so between the light blue and dark green curves. Note the y axis increases downwards. The three pairs of graphs correspond to three definitions of twilight.

If you're viewing from a vehicle doing 60mph on the A55, you lengthen the twilight by about 10% if going west, or shorten it if going east.
fras
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Re: A55 - today a real express way !

Post by fras »

Many thanks to our resident experts ! I suppose this is why we get such wonderful red sunsets around this time.
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