In an attempt to express absolute certainty, one often hears the expression that "I am as sure as I am certain
that the sun will rise tomorrow". Of course, with each sunrise, we have an even more majestic sunset. Aside from
signalling the end of the day, the setting sun helps accentuate many features of the atmosphere during the few
minutes it approaches and later dips below the horizon including rich and colorful patterns in the lower parts
of the atmosphere which invariably are immune to our eyes and yet produce vivid colors and patterns on film
emulsion. Another equally dramatic experience is the rising moon which is often characterized with a "bloody"
red or dark
orange appearance.
Although most people associate the setting of the sun with the end of day and the beginning of darkness, we also
have civil, nautical and astronomical twilight which are also used to indicate the end of day and absence of light.
Civil twilight technically occurs when the sun is between 0 and 6 degrees below the horizon; it is when people
first sense "complete" darkness and car headlights must be turned on in most places of the world. Similarly,
nautical twilight is defined to occur when the sun is between 6 and 12 degrees below the horizon and, as the
term suggests, someone at sea would not be able to distinguish the horizon during this time, thus rendering the
use of sextants, for example, useless. Finally, astronomical twilight is when the sun is at least 12 degrees
below the horizon and signals the start of the greatest possible darkness that one can expect during the evening
(barring the possible influence of the moon in the sky) and is of great interest, for example, to astrophotographers.
Body: Sun Mass: 332,900 x Earth Mean Eq Diameter: 109.1 x Earth Distance: 152 million km RA / Dec: 06h 00m 14s / 23° 26' Diameter: 31.48' Magnitude: -26.8 |
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Date: May 23, 1999 19:52 UT+3 Location: Isle of Mykonos, Greece Equipment: Canon A-1 Canon 50mm @ f11 Fuji Superia 400 Exposure: 1/125th sec Software: Photoshop V6 Processing: Cropping JPG Compression |