sunset
when the sun sets is a pretty big deal for many relegions.
check out the 'discussion' that was email from our communications department as they are preparing next years callendar and choosing 'sunset times' to put in it.
I have not got a clear answer on how many degrees they have adopted.
------begin email -----
I came across these definitions for sunset while researching sunset times for the Trust department's sunset calendar. These definitions may come in handy for those who need a few more minutes on Friday to finish washing the car, mowing the lawn, or vacuuming the carpet. :-)
SunriseSunset.com
Sunset Definitions
Civil Twilight
Civil twilight is defined when the sun is 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.
Nautical Twilight
Nautical twilight is defined when the sun is 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct.
Astronomical Twilight
Astronomical twilight is defined when the sun is 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the sun does not contribute to sky illumination; for a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible.
check out the 'discussion' that was email from our communications department as they are preparing next years callendar and choosing 'sunset times' to put in it.
I have not got a clear answer on how many degrees they have adopted.
------begin email -----
I came across these definitions for sunset while researching sunset times for the Trust department's sunset calendar. These definitions may come in handy for those who need a few more minutes on Friday to finish washing the car, mowing the lawn, or vacuuming the carpet. :-)
SunriseSunset.com
Sunset Definitions
Civil Twilight
Civil twilight is defined when the sun is 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.
Nautical Twilight
Nautical twilight is defined when the sun is 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct.
Astronomical Twilight
Astronomical twilight is defined when the sun is 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the sun does not contribute to sky illumination; for a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible.
posted by forkev at 1/31/2005 03:27:00 PM
1 Comments:
the sun at 0 degrees is our adopted definition of sunset here. cool. i got my clear answer. I wish that had been in the email.
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