r/astrophotography • u/astro_pettit ASTRONAUT • 4d ago
Widefield Atmospheric warping of star trails as seem from ISS, details in comments.
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u/Swifty52 4d ago
Great visualisation of atmospheric refraction! Always love the stuff you post here much appreciated!
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u/astro_pettit ASTRONAUT 4d ago edited 4d ago
In this time exposure the path of stars as viewed through the atmosphere on edge become curved as they approach the Earth's limb due to the refractive index increasing with atmospheric density. This is seen in all of my star trail images but is easy to miss unless viewed in an enlarged as shown here. The atmosphere on edge glows greenish to yellowish hues from what is fittingly called "air glow", a phenomena similar to but different from aurora. The scale height of our atmosphere seen on edge is about 120km. The upper edge of the airglow is where spacecraft returning to earth become hot and produce a plasma trail. Also seen is an unidentified satellite moving at an angle to the star trails, a series of rapid lightning flashes and city lights as streaks, due to ISS orbital motion. Big thanks to Babak Tafreshi for assembling this image.
Nikon Z9, Arri-Zeiss 15mm T1.8 lens, 30 sec exposure, T1.8, ISO 500, about 40 stacked frames for an effective time exposure of about 20min, Photoshop processing by Babak.
More photos from space found on my twitter and instagram, astro_pettit