Star trails are really arcs, or partial circles, whose ever-circling motions forever tabulate the passage of time. Each and every star moves 15 degrees westward in one hour. Stars near the celestial poles produce the smallest circles while those near the celestial equator produce the largest. The stars – like the sun during the daytime – move from east to west across the sky every night. What this means is that, if you’re standing out under the stars, you see them move across the sky as the night progresses. In fact, the stars move counter-clockwise around the sky’s north pole in the course of every night. Thank you, Guy! If you aim your camera northward in a long-exposure photo, the star trails will be seen to track around the north celestial pole. | Star trails (plus meteor) photo taken by Guy Livesay. He wrote: “Polaris star trail with an Orionid meteor (possibly) in the bottom left.” Thanks, Cameron! Star trails over the planned site of the Giant Magellan Telescope in the Atacama Desert in Chile. | Cameron Frankish captured this image in Dartmoor, Devon, UK, on October 21, 2019. View larger at EarthSky Community Photos. So, as seen from Earth, all the stars go full circle and return to the same place in the sky after this period of time, which astronomers call a sidereal day – a revolution with respect to the stars. The Earth makes a complete rotation relative to the backdrop stars in a period of about 23 hours and 56 minutes. Star trails reflect Earth’s rotation, or spin, around its axis. ![]() ![]() There are also many variations on star trail photos, as you’ll see here! Then, with an open shutter, the camera records an image as Earth turns on its axis and the stars move overhead. ![]() Often, the camera stays pointed at Polaris, the North Pole Star, or at the south celestial pole (not marked by a single star) in the Southern Hemisphere. With a steady mount, long exposures and a few other tricks, photographers can take images of star trails, showing the motion of the stars over the sky during a period of minutes or hours. He wrote: “Polaris time lapse captured a single, impressive Draconid meteor streak over the Ottawa River at Deep River Ontario, Canada, early in the evening of October 8, 2021.” Thank you, David! What are star trails? | David Cox in Deep River Ontario, Canada, captured this photo of star trails and a Draconid meteor on October 8, 2021.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |