On the matter of Civil Twilight
FROM TODAY'S PRINT EDITIONS:
Joe Bollinger, in Glen Burnie, asks: “What time did twilight begin and end on June 21st, and is the length of twilight the same on the winter solstice?” Civil Twilight begins when the center of the sun’s disk is 6 degrees below the horizon, and ends when it’s 6 degrees below the horizon after sunset.
Civil Twilight on June 21 began at 5:08 a.m. EDT, 32 minutes before sunrise. It ended at 9:09 p.m., 32 minutes after sunset. On the winter solstice, Dec. 22, twilight will be 30 minutes long.
(SUN PHOTO: Jed Kirschbaum, 2008)
Posted by Frank Roylance at 12:02 AM | Permalink
| Comments (1)
Categories: From the Sun's print edition, Sky Notes
Categories: From the Sun's print edition, Sky Notes
Comments
The definition of civil twilight is inadequate to describe actual twilight. It's clear that the sky starts to lighten at least an hour before sunrise in June. Likewise, at night, it does not get completely dark for at least an hour after sunset.
FR: That's why there are also definitions for Nautical and Astronomical Twilight. http://en.wikipedia.org/wiki/Twilight
Posted by: Bernard P. Codd | June 28, 2011 7:03 AM