Today's twilights and dusks
Monday, 5 September 2016
The idea for The New Almanac came from a desire to be more in touch with the world around me, just in very simple ways like: when is the sun coming up tomorrow? What is that bright star in the sky? Today I’ve been thinking about and researching dusk, and there’s a phrase I don’t get to say every day. In recent days dusk has rushed in, a definite change from the light evenings of summer, and through September it keeps on tumbling, reminding us even on beautiful days that the sun is on the wane and different times are coming.
Twilight and dusk are beautiful, evocative words and times. They are also little more complex than you might think. So here are civil twilight, nautical twilight and astronomical twilight and their dusks explained, followed by the times you can expect each tonight.
Civil twilight and dusk: such a polite term, and so expressive of the period when the light starts to fade, but you can still comfortably go about your business without the need for artificial light. I see neighbours gardening in proximity and chatting over the garden fence during civil twilight. More precisely, it means the time between sun set and the moment that the sun is 6 degrees below the horizon. The moment that it reaches 6 degrees below is called civil dusk.
Nautical twilight and dusk: the term dates back to when sailors used the stars for navigation, because during nautical twilight – the spell when the sun is between 6 and 12 degrees below the horizon – most stars can be seen with the naked eye. Nautical dusk is the moment the sun reaches 12 degrees below.
Astronomical twilight and dusk: The sun is between 12 and 18 degrees below the horizon, and this is the spell when there is still a little light in the sky, but before true dark. After astronomical dusk at 18 degrees below, all stars will be visible.
So this evening, 5th September, Birmingham time (chosen simply because Brum is neither north nor south, so it’s a decent approximate), look out for:
Civil twilight beginning at 7.45pm and ending at 8.21pm
Nautical twilight beginning at 8.21pm and ending at 9.03pm
And Astronomical twilight starting at 9.03pm and ending at 9.47pm
If I want to go twilight gardening, moth spotting or star watching, I know exactly when to do it. And if you would like to have this sort of day-to-day knowledge of the turning of the earth in your hands, please consider pledging to support The New Almanac. In the meantime, enjoy the gloaming.
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