|
|
|
Thread Tools | Display Modes |
|
#1
|
|||
|
|||
What is the Darkest Hour of the Night?
|
#2
|
|||
|
|||
Eugene Shubert (or somebody else of the same name) wrote thusly in message
: What is the darkest hour of the night? Eugene Shubert http://www.everythingimportant.org Isn't it supposed to be just before dawn? Sounds unlikely on scientific grounds though, so I'd say it's around the (real local) midnight. -- Paul Townsend Pair them off into threes Interchange the alphabetic letter groups to reply |
#3
|
|||
|
|||
Prai Jei wrote in message ...
Eugene Shubert (or somebody else of the same name) wrote thusly in message : What is the darkest hour of the night? Eugene Shubert http://www.everythingimportant.org Isn't it supposed to be just before dawn? Yes. Sounds unlikely on scientific grounds though, so I'd say it's around the (real local) midnight. Googling the phrase "It's always darkest before dawn" turn up 1750 hits. An astronomer should know when it really is the darkest hour of the night. I'm looking for a confident, scientifically measured answer, not a reasonable guess. Eugene Shubert http://www.everythingimportant.org |
#4
|
|||
|
|||
|
#6
|
|||
|
|||
"Mr. 4X" wrote in message ...
(Eugene Shubert) wrote in message om: What is the darkest hour of the night? That depends on a lot of things. There is almost no direct sunlight 2-3 hours after sunset, Isn't there a measurable amount of sunlight that's scattered by the atmosphere, reaching further into the night than a mere 2-3 hours of earth rotation? When a sizable part of the earth's surface and atmosphere is heated up during the day, doesn't a measurable fraction of that heated material reradiate energy in the visible spectrum? To keep the calculations simple, let's ignore artificial lighting but factor in the reflected light of the Moon if you know how to do that. Eugene Shubert http://www.everythingimportant.org |
#7
|
|||
|
|||
"Eugene Shubert" wrote in message om... "Mr. 4X" wrote in message ... (Eugene Shubert) wrote in message om: What is the darkest hour of the night? That depends on a lot of things. There is almost no direct sunlight 2-3 hours after sunset, Isn't there a measurable amount of sunlight that's scattered by the atmosphere, reaching further into the night than a mere 2-3 hours of earth rotation? Zodiacal light. When a sizable part of the earth's surface and atmosphere is heated up during the day, doesn't a measurable fraction of that heated material reradiate energy in the visible spectrum? To keep the calculations simple, let's ignore artificial lighting but factor in the reflected light of the Moon if you know how to do that. It will be darkest at local midnight in midwinter when the Moon is new and Venus is below the horizon. I wonder how often that combination occurs (if ever). George |
#8
|
|||
|
|||
"George Dishman" wrote in message ...
"Eugene Shubert" wrote in message om... "Mr. 4X" wrote in message ... (Eugene Shubert) wrote in message om: What is the darkest hour of the night? That depends on a lot of things. There is almost no direct sunlight 2-3 hours after sunset, Isn't there a measurable amount of sunlight that's scattered by the atmosphere, reaching further into the night than a mere 2-3 hours of earth rotation? Zodiacal light. I thought that the zodiacal light was scattered off of Solar System dust in the plane of the ecliptic, rather than Earth's atmosphere? When a sizable part of the earth's surface and atmosphere is heated up during the day, doesn't a measurable fraction of that heated material reradiate energy in the visible spectrum? To keep the calculations simple, let's ignore artificial lighting but factor in the reflected light of the Moon if you know how to do that. It will be darkest at local midnight in midwinter when the Moon is new and Venus is below the horizon. I wonder how often that combination occurs (if ever). How can Venus *not* be below the horizon at local midnight? Venus reaches a maximum elongation of about 48 degrees relative to the Sun. If I've done the math correctly, Venus should always be below the horizon by 3 hours and 12 minutes after sunset. George -- Rainforest laid low. "Wake up and smell the ozone," Says man with chainsaw. John J. Ladasky Jr., Ph.D. |
#9
|
|||
|
|||
John Ladasky writes:
George Dishman wrote: It will be darkest at local midnight in midwinter when the Moon is new and Venus is below the horizon. I wonder how often that combination occurs (if ever). How can Venus *not* be below the horizon at local midnight? Venus reaches a maximum elongation of about 48 degrees relative to the Sun. If I've done the math correctly, Venus should always be below the horizon by 3 hours and 12 minutes after sunset. For locations near the equator, yes. Near the poles, however, it is possible for the Sun to be down and Venus to be up at local midnight. |
#10
|
|||
|
|||
"John Ladasky" wrote in message om... "George Dishman" wrote in message ... "Eugene Shubert" wrote in message om... "Mr. 4X" wrote in message ... (Eugene Shubert) wrote in message om: What is the darkest hour of the night? That depends on a lot of things. There is almost no direct sunlight 2-3 hours after sunset, Isn't there a measurable amount of sunlight that's scattered by the atmosphere, reaching further into the night than a mere 2-3 hours of earth rotation? Zodiacal light. I thought that the zodiacal light was scattered off of Solar System dust in the plane of the ecliptic, rather than Earth's atmosphere? Yes, I was unclear. When Eugene said "Isn't there a measurable amount of sunlight that's scattered ..." I wondered if he was recalling discussion of the Zodiacal light rather than atmospheris scatter. I was too economical with my words (most unusual). It will be darkest at local midnight in midwinter when the Moon is new and Venus is below the horizon. I wonder how often that combination occurs (if ever). How can Venus *not* be below the horizon at local midnight? Venus reaches a maximum elongation of about 48 degrees relative to the Sun. If I've done the math correctly, Venus should always be below the horizon by 3 hours and 12 minutes after sunset. Again I stand corrected. It should have been obvious to me since Venus is inside our orbit. Thanks for picking me up on those. best regards George |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
NEBRASKA STAR PARTY Report | David Knisely | Amateur Astronomy | 3 | August 5th 04 10:34 PM |
Thanks George | Oriel36 | Astronomy Misc | 31 | January 5th 04 02:16 PM |
Local Siderial Time? | Roger Hamlett | Misc | 17 | January 2nd 04 04:18 PM |
My Darkest Night | Starlord | Amateur Astronomy | 4 | September 27th 03 11:11 PM |
Deepsky 2003 Astronomy Software vs Starry Night | GO VOLS! | Amateur Astronomy | 9 | September 7th 03 04:35 PM |