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An interesting thread. I don't know much about this, but I can tell you that here in the Southern Hemisphere, places at higher latitudes than 48 S are almost all of them here in South America (Argentina and Chile). Cities like RÃo Gallegos (51 S), El Calafate (50 S), RÃo Grande (53 S), Ushuaia (54 S). I was in RÃo Gallegos and El Calafate once in late January, and to tell you the truth, when it was dark, it was dark. I didn't notice anything strange, apart from the fact that the sun sets very late! I also was in London in late July/early August, and the same happened. So, as someone suggested in this thread, to the non-astronimical eye, this is not noticeable.
With solar midnight at about 1.30am, and permanent nautical twilight, one can see twilight at 00:00 1st January in Ushuaia
In Summer Solstice,
48°36N or above = Astronomical Twilight
54°36N or above = Nautical Twilight
60°36N or above = Civil Twilight
Exactly.
Astronomical twilight means dark sky for most casual observers. Nautical twilight means that the sky is mostly dark, but navigation via the horizon should still be possible without clouds and with a good visibility; that means that, on a clear midnight at the summer solstice, skies begin to become noticeably brighter at 56°-57°, but at that latitude one should only be able to see a very short period of slightly brighter skies around midnight. I once went to Edinburgh and even the Scottish Highlands up to 58°N in early July and in the middle of the night the sky was unquestionably dark. I actually believe that 99% of Edinburghers do not notice any difference.
If one wants to experience periods of true white nights, then he has to go from 59°-60°N northwards; specifically from 62°-63° (the latitude of cities like Trondheim or Kuopio) it becomes possible to keep the lights off inside the houses all through the night with clear skies.
Besides, midnight is rarely the darkest moment of the night, due to the effects of daylight saving time and possibly longitude combined.
I think that considering that time of year is coming up again there are enough people on this forum who live in the mid-50s latitudes upwards for us to be able to go by personal observations of what we can see rather than argue about precise definitions of different stages of twilight.
I live fractionally below 54 N, and on clear nights near the solstice the northern horizon is bright enough that the outlines of clouds are illuminated and there is a mauve tint to part of the sky. Some nights have it brighter than others and there is more to how bright the midnight sky is than just how close you are to the solstice. Essentially it is still dark for all practical purposes, and you have to go looking for the light to really notice it, and you won't notice anything at all on an overcast night, but there is something there, and something that I couldn't notice living in the south of England at 51.5 N, so I believe the effect starts to become noticeable somewhere near the 53rd parallel.
I've tried taking photos of it, but my camera doesn't do low light conditions well enough to do it justice. I'll be going to the Scottish Highlands in the last week in June this year and I'll be interested to observe how bright the night skies are there.
here's one i took 25th June last year 2:06 (about the darkest time of the night) during mostly clear conditions.
latitude is 57°42'N
you can see vague contours of objects if you're out walking, but you definetly need extra-light lol.
Ah right, that's almost exactly the same latitude as where I'm going in Scotland. Not as bright as I was expecting, but still better than here and impressive enough for the middle of the night.
here's one i took 25th June last year 2:06 (about the darkest time of the night) during mostly clear conditions.
latitude is 57°42'N
you can see vague contours of objects if you're out walking, but you definetly need extra-light lol.
2:06 ---> darkest time of the night?
I assume you meant 1:06
I've just checked that Goteborg's solar noon on 25th June 2013 was at 13:15 so that the solar midnight would be around 1:15, so the darkest time of the night would be around that time
2:06 ---> darkest time of the night?
I've just checked that Goteborg's solar noon on 25th June 2013 was at 13:15 so that the solar midnight (darkest time if the night) would be 1:15am
that's probably correct. even a bit darker than the picture posted then.
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