Sorry for the late report but there was something a little unusual at
sunset last night as observed from hills just west of Winchester.
Visibility was generally goodish but towards the WNW (where the sun
was going down) was a patch of quite thick haze. The sun dimmed
noticeably as it sank through that haze, and then became brighter
again as it emerged from it. It was definitely not a cloud effect -
the sun looked like it did on a hazy day as it sank through the haze
rather than looking as it does through cirrus. I also thought I saw
what looked like smoke emanating from very low in the WNW, in the
clearer air below the haze patch. Would this have been a patch of
water vapour from a chimney somewhere (at an estimate, the Bristol
area), forming a small patch of poor visibility?

Nick