Joe Egginton wrote:

I went up Bushbury Hill (613ft) yesterday, and noticed the air is quite
dirty. I could just about see the outline of the Wrekin 20 miles away.
Blue sky above at the zenith, dirty grey at the horizon.

It had methinks, at the distance of 20 miles what's difference between the
true and astronomical horizon?


On Sunday I drove over the Cat & Fiddle road to Macclesfield. The summit (515m)
was just at the top of the haze. There was clear deep blue sky above but
everywhere below was filled with grey/brown crud.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.