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# 654 ≡ Re: ...dernières nouvelles du cosmos ...

Groupe I

5900 posts depuis
le 4/7/2010

Taylor Photography

Nature & Man: Iridium Flare, Milky Way, Clouds and Light Pollution

What is an Iridium flare?

Iridium flares are often mistaken for meteors because of their notable bright flashes of light in the night sky but they are actually caused by a specific group of satellites that orbit our planet. An Iridium flare is a specific type of satellite flare that is made when the antennas of an Iridium communication satellite reflect sunlight directly onto the surface of the Earth. The satellites are in a near-polar orbit at an altitude of 485 miles and their orbital period is approximately 100 minutes with a velocity of 16,800 miles per hour. The uniqueness of Iridium flares is that the spacecraft emits 'flashes' of very bright reflected light that sweep in narrow focused paths across the surface of the Earth. An Iridium communication satellite's Main Mission Antenna is a silver-coated Teflon antenna array that mimics near-perfect mirrors - the array is angled at 40 degrees away from the axis of the body of the satellite. This can provide a specular reflection of the Sun's disk, periodically causing a dazzling glint of reflected sunlight. At the Earth's surface, the specular reflection is probably less than 50 miles wide, so each flare can only be viewed from a fairly small area. The flare duration can last from anywhere between 5 to 20 seconds and can easily be seen by the naked eye.

Sources:
http://www.ph.surrey.ac.uk/satellites/main/project2_4.html
http://www.space.com/6898-reflections-space-spot-iridium-flares.html
http://www.wikihow.com/Find-an-Iridium-Flare

This image is one 30 second frame from a time lapse of the Milky Way & other features of the night sky in motion against a silhouetted foreground. Photographed from an undisclosed location in Western Maine, this shot includes quite a bit of light pollution & some fast moving cloud cover. Most of the light pollution in this image is coming from Farmington, Maine which is about 35 miles from this location. The footage from this time lapse will be featured in my upcoming short film Shot In The Dark.

Nikon D600 & 14-24 @ 14mm
f/2.8 - 30 secs - ISO 3200 – WB Kelvin 3570
06/23/14 – 11:07PM
Processed via Lightroom 5 & Photoshop CS5

Prints & Portfolio: http://goo.gl/hxKp3C
On 500px: http://500px.com/photo/74939175
On Flickr: http://goo.gl/KI5xv4

2014 Night Photography Workshops: http://goo.gl/158Ntf

© Mike Taylor - Taylor Photography
http://miketaylorphoto.com/

Cheers! Feel free to share this image if you dig it and thanks for your support.

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12.11.14 - 04:45

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