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Post by flash on May 11, 2009 22:03:34 GMT -7
This evening just after sunset we had a pass of the International Space Station.This was at the beginning of nautical twilight so the sky was very bright.I was unable to pick up the Progress resupply spacecraft which was setting just behind the ISS and will dock with the station tomorrow afternoon. Enjoy the show! ;D www.youtube.com/watch?v=XJYWX4OxS1AThomas the Flash
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Post by Tim Collins on May 12, 2009 3:52:09 GMT -7
This evening just after sunset we had a pass of the International Space Station.This was at the beginning of nautical twilight so the sky was very bright.I was unable to pick up the Progress resupply spacecraft which was setting just behind the ISS and will dock with the station tomorrow afternoon. Enjoy the show! ;D www.youtube.com/watch?v=XJYWX4OxS1AThomas the Flash
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rosa
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Post by rosa on May 12, 2009 4:39:10 GMT -7
somebody please explain: nautical twilight
thanks
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Post by flash on May 12, 2009 5:37:44 GMT -7
Rosa There are three twilights.Civil Twilight comes 30 minutes after sunset or before sunrise.Nautical twilight comes just a little less than an hour after sunset or a littles less than an hour before sunrise. Astronomical twilight is a little less than an hour and a half after sunset or before sun rise. These twilight are based on how far the Sun is below the observer's horizon. Like for today, Civil Twilight ends or begins when the Sun is 6 degrees below an observer's horizon. Nauical Twilight ends or begins when the Sun is about 12 degrees below an observer's horizon. Astronomical Twilight ends or begins when the Sun is about 18 degrees below an observer's horizon. Civil Twilight is when the sky is the brightest after sunset or before sunrise. Astronomical twilight is when the sky is fully dark. Thomas the Flash
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Post by flash on May 12, 2009 7:02:26 GMT -7
One note I would like to make about the video.Near the end of the video you can see the ISS passing ,what looks like, below the clouds.This is an optical illusion caused by the camera.The camera is not a standard video camera most have seen and used but a very low light video camera.The camera can see in visible light but is more sensitive to the red and near infra-red end of the spectrum. Visually the cloud you see in the video were very thin but the camera I was using was picking up more of the heat signature off the water vapor around the cloud. The ISS having a brighter heat signature was able to punch through the heat signature of the water vapor giving the visual impression in this video that the ISS was flying below the clouds. Believe me had this been an airplane you would have had no problems seeing the safety light strobes on an aircraft. Thomas the Flash
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rosa
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Post by rosa on May 12, 2009 16:42:59 GMT -7
Rosa There are three twilights.Civil Twilight comes 30 minutes after sunset or before sunrise.Nautical twilight comes just a little less than an hour after sunset or a littles less than an hour before sunrise. Astronomical twilight is a little less than an hour and a half after sunset or before sun rise. These twilight are based on how far the Sun is below the observer's horizon. Like for today, Civil Twilight ends or begins when the Sun is 6 degrees below an observer's horizon. Nauical Twilight ends or begins when the Sun is about 12 degrees below an observer's horizon. Astronomical Twilight ends or begins when the Sun is about 18 degrees below an observer's horizon. Civil Twilight is when the sky is the brightest after sunset or before sunrise. Astronomical twilight is when the sky is fully dark. Thomas the Flash awesome! Thanks Thomas
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