Iridium Flare over St Peter's Church - Unretouched : 無料・フリー素材/写真
Iridium Flare over St Peter's Church - Unretouched / Dominic's pics
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
|---|---|
| 説明 | An image of an Iridium flare over the spires of St Peter's Church, Brighton. Even over the few seconds needed to capture the transit of the satellite, it is possible to discern the blurring of the stars caused by the rotation of the earth. The little fine wiggles of the flare are probably the result of vibration caused by road traffic close to the camera and tripod.Because the Iridium Flares are dim compared to an urban environment this image has been presented as part of a pair of images on the photostream. One is un-retouched, the other has the flare emphasised in comparison to the surrounding environment.Iridium flares are narrow sunlight glints off the door sized, flat, shiny, phased array antennae of passing Iridium Communications Satellites. They tend to be brightest just after dusk, or just before dawn. The image was captured in an urban environment. Without special tripod astronomical calibration (accurately setting the altitude - how high up to angle the camera, and the azimuth - how far round from north to angle the camera), it is difficult to point a camera accurately at the anticipated location in the sky where the flare will appear . Consequently the temptation is to set a wide angle of view to avoid missing the event, and hence often a smaller image results.I try to use a protractor to draw a line through a landmark on a Google Map printout to help set up the camera, and also to estimate the altitude angling for the camera. The flares only last a few seconds.A constellation of 66 satellites - the Iridium network embraces the earth at a fast and low altitude, orbiting pole to pole. They are used to enable satellite mobile phone communications in remote locations such as, for example, Antarctica. The constellation includes its own network "backhaul" - relaying signals from satellite to satellite until contact can be made back to the appropriate earth location.It is possible to predict when Iridium flares will appear - assuming good visibility. The excellent "Heavens Above" website normally gives good predictions - provided that the location of the observer is accurately supplied. (Sometimes the individual satellites need to re-manoeuvre back into place as a consequence of slight atmospheric drag - which can temporarily throw off projected locations).The Iridium constellation lays claim to being the the first one to share an accidental "satellite crash" with another satellite. The event on the 10th February 2009 (Iridium 33 colliding with Cosmos 2251 at over 26,000 miles an hour) is spectacularly re-enacted on YouTube. |
| 撮影日 | 2009-07-11 22:03:24 |
| 撮影者 | Dominic's pics |
| タグ | |
| 撮影地 | Brighton, England, United Kingdom 地図 |