diamond geezer

 Saturday, October 28, 2006

"It's getting dark earlier isn't it?"
"And it'll be even darker tomorrow when the clocks go back."
"Still, at least it'll be a bit lighter in the mornings."

Here's a scarily-detailed response to the above conversation...

A brief classification of darkness*
• Sunset
: the time at which the centre of the sun slips beneath the horizon.
Civil twilight: the period during which the centre of the Sun is less than 6 degrees below the horizon. Outdoor objects can still be clearly distinguished, the horizon is clearly defined and the brightest stars are visible. It's not completely dark.
Nautical twilight: the period during which the centre of the sun is between 6 and 12 degrees below the horizon. Outlines of outdoor objects may be distinguishable, but detailed outdoor operations are not possible and the horizon is indistinct. It's nearly completely dark.
Astronomical twilight: the period during which the centre of the Sun is between 12 and 18 degrees below the horizon. Illumination of the sky is practically imperceptible. It's completely dark, unless you're an astronomer.
Darkness: the period during which the centre of the Sun is more than 18 degrees below the horizon. It's pitch black.
(* under good atmospheric conditions in the absence of moonlight or other illumination)

How dark is it at 6pm?
Daylight: 17 March → 18 October
Sunset: 19 October (ie last week)
Civil twilight: 20 October → 28 October (would have been longer, but the clocks go back tomorrow)
Nautical twilight: (skipped when the clocks go back)
Astronomical twilight: 29 October → 24 November (suddenly very dark)
Pitch black: 25 November → 24 December
Astronomical twilight: 25 December → 28 January
Nautical twilight: 29 January → 20 February
Civil twilight: 21 February → 15 March
Sunset: 16 March (before the clocks go forward)

How dark is it at 5pm?
Daylight: 8 February → 28 October (and then the clocks go back)
Civil twilight: 29 October → 6 November
Nautical twilight: 7 November → 15 January (it never gets completely dark)
Civil twilight: 16 January → 6 February
Sunset: 7 February

How dark is it at 7am?
Daylight: 24 February → 20 October
Sunrise: 21 October (ie last week)
Civil twilight: 22 October → 28 October (and then the clocks go back)
Daylight: 29 October → 4 November (yes, it really is daylight again)
Sunrise: 5 November (but not for long)
Civil twilight: 6 November → 28 November
Nautical twilight: 29 November → 3 February (it never gets completely dark)
Civil twilight: 4 February → 22 February
Sunrise: 23 February

>> All figures are for London - even though it's never dark in sodium-glow London
>> Further in-depth information about twilight can be found here, here, here and here
>> You can find day-by-day twilight details for London here, and other world locations here

<< click for Newer posts

click for Older Posts >>

click to return to the main page

...or read more in my monthly archives
Jan20  Feb20  Mar20  Apr20  May20
Jan19  Feb19  Mar19  Apr19  May19  Jun19  Jul19  Aug19  Sep19  Oct19  Nov19  Dec19
Jan18  Feb18  Mar18  Apr18  May18  Jun18  Jul18  Aug18  Sep18  Oct18  Nov18  Dec18
Jan17  Feb17  Mar17  Apr17  May17  Jun17  Jul17  Aug17  Sep17  Oct17  Nov17  Dec17
Jan16  Feb16  Mar16  Apr16  May16  Jun16  Jul16  Aug16  Sep16  Oct16  Nov16  Dec16
Jan15  Feb15  Mar15  Apr15  May15  Jun15  Jul15  Aug15  Sep15  Oct15  Nov15  Dec15
Jan14  Feb14  Mar14  Apr14  May14  Jun14  Jul14  Aug14  Sep14  Oct14  Nov14  Dec14
Jan13  Feb13  Mar13  Apr13  May13  Jun13  Jul13  Aug13  Sep13  Oct13  Nov13  Dec13
Jan12  Feb12  Mar12  Apr12  May12  Jun12  Jul12  Aug12  Sep12  Oct12  Nov12  Dec12
Jan11  Feb11  Mar11  Apr11  May11  Jun11  Jul11  Aug11  Sep11  Oct11  Nov11  Dec11
Jan10  Feb10  Mar10  Apr10  May10  Jun10  Jul10  Aug10  Sep10  Oct10  Nov10  Dec10 
Jan09  Feb09  Mar09  Apr09  May09  Jun09  Jul09  Aug09  Sep09  Oct09  Nov09  Dec09
Jan08  Feb08  Mar08  Apr08  May08  Jun08  Jul08  Aug08  Sep08  Oct08  Nov08  Dec08
Jan07  Feb07  Mar07  Apr07  May07  Jun07  Jul07  Aug07  Sep07  Oct07  Nov07  Dec07
Jan06  Feb06  Mar06  Apr06  May06  Jun06  Jul06  Aug06  Sep06  Oct06  Nov06  Dec06
Jan05  Feb05  Mar05  Apr05  May05  Jun05  Jul05  Aug05  Sep05  Oct05  Nov05  Dec05
Jan04  Feb04  Mar04  Apr04  May04  Jun04  Jul04  Aug04  Sep04  Oct04  Nov04  Dec04
Jan03  Feb03  Mar03  Apr03  May03  Jun03  Jul03  Aug03  Sep03  Oct03  Nov03  Dec03
 Jan02  Feb02  Mar02  Apr02  May02  Jun02  Jul02 Aug02  Sep02  Oct02  Nov02  Dec02 

eXTReMe Tracker
jack of diamonds
Life viewed from London E3

» email me
» follow me on twitter
» follow the blog on Twitter
» follow the blog on RSS

my flickr photostream