GeoStationary HighWay

Babak A. Tafreshi


Geostationary Orbits are over five times the radius of the Earth, approximately 36000 km above sea level. Objects in such orbits have orbital period equal to the Earth's rotation and would remain stationary over the same point on the Earth's equator. Geostationary objects appear motionless in the sky, making extremely useful for communications (including TV broadcast) and weather satellites. While in 1945 Arthur C. Clark was the first to suggest the usefulness of such an orbit, there are now over 370 satellites in Geostationary orbits. But while they are motionless relative to the Earth surface, they are moving objects against the background sky as they are rotating around our planet in this space high way with speed ten times faster than an airliner. Although they are some of the farthest satellites, but surprisingly, given dark enough skies, it is possible, armed with a telescope or a pair of binocular to spot some of the them in the geostationary ring. Typically these satellites are at magnitude. +11 or fainter (over 100 times fainter than naked-eye visibility), but as recorded in this video they are brightening by several magnitudes when the geometry is favorable. Most satellites in the video are at 7th to 9th magnitudes but there are few of them at about magnitude 5, visible to the naked-eye under dark skies! The time-lapse video is made using an 85mm lens on a modified DSLR camera under an ideal dark sky. It is a sequence of 12 shots each 45s exposure on a tracking mount. Majority of GeoSats are visible at 5 degrees below the equator on the Orion Nebula declination. Mintaka , the western most star of the Orion Belt, is the closest to the equator. All of the satellites in this highway has moved about 2.5 degrees during the 10 minute shooting period, equal to 360 degrees for a complete 24 hours. Babak Tafreshi


GeoSatellites observing resource


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