130809 - Milky Way transit over Saline Bay
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click 'Play' for a 1½ minute video
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ASTRO:
type=(Milky Way) Barred Spiral galaxy, const=Scorpio, Sagittarius, Aquila, Ophiuchus, (galaxy core nucleus), mag=-20.9 (integrated), dist=27k ly, size=185k ly IMAGE: location=EB lakeside bulkhead BrtlCls=5; exposure=DSLR OSC: 1140x25s (9.5h), f/2.8, ISO3200 EQUIPMENT: camera=Nikon D90 (stk); optics=NIKKOR 24-105mm zoom set @ 24mm, f/5.6 filter=(none); mount=simple tripod SOFTWARE: acquisition=Nikon Camera Control Pro 2 processing=LrC, PS Producer |
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To the casual observer, normal glances at the nighttime sky yield no perception of its apparent movement. Stars and the Moon seem to just "sit there", with our impatience quickly getting the best of us and causing our minds and our eyes to quickly look elsewhere for 'action'. It's a natural reflex. Scientists believe it is part of our 'original animal programming' from when we were still wanderers and gatherers, always on the lookout for food and predators. But because the sky's motion is caused by the rotation of the Earth (the celestial spinning ball we are all firmly standing on), the sky is actually moving at all times. Exhibiting an 'apparent' movement that is almost imperceptible to the naked (unaided) eye, it (the sky) actually moves at a rate of appx 15 arc-degrees per hour. ...and with the apparent movement from East to West resulting from the Earth's rotation in the opposite direction toward the East.
In the accompanying short video, the sky's apparent motion is captured thru a photographic technique called 'Time-Lapse Photography'. A common video camera designed to take motion pictures during the daytime is challenged with capturing this motion at night; because, any given 'frame' of the video is exposed so quickly, it cannot capture the faint details of the stars, planets and Milky Way. But by slowing the acquisition process down, individual long exposures can be given the time needed to capture those details.
This video is comprised of 1,140 individual digital exposures captured with a DSLR camera mounted on a simple fixed tripod with a laptop computer for capture and control. Each exposure is 25s in duration, with a 5s 'rest' period in-between. By using computer software to sequence them into a video stream, each exposure is slotted into a 0.04s stream of views (equivalent to 25FPS). The process effectively compresses appx 9.5 hours of exposures (from dusk till dawn) into just 1:34m to make the movement clearly visible.
The capture was made from inside the Emerald Bay community, looking south along the shoreline of Saline Bay on Lake Palestine, Texas. Watch to catch the core of the Milky Way as it transits across the nighttime sky.
In the accompanying short video, the sky's apparent motion is captured thru a photographic technique called 'Time-Lapse Photography'. A common video camera designed to take motion pictures during the daytime is challenged with capturing this motion at night; because, any given 'frame' of the video is exposed so quickly, it cannot capture the faint details of the stars, planets and Milky Way. But by slowing the acquisition process down, individual long exposures can be given the time needed to capture those details.
This video is comprised of 1,140 individual digital exposures captured with a DSLR camera mounted on a simple fixed tripod with a laptop computer for capture and control. Each exposure is 25s in duration, with a 5s 'rest' period in-between. By using computer software to sequence them into a video stream, each exposure is slotted into a 0.04s stream of views (equivalent to 25FPS). The process effectively compresses appx 9.5 hours of exposures (from dusk till dawn) into just 1:34m to make the movement clearly visible.
The capture was made from inside the Emerald Bay community, looking south along the shoreline of Saline Bay on Lake Palestine, Texas. Watch to catch the core of the Milky Way as it transits across the nighttime sky.