Seeing the Sky in Correct Proportions

November 23, 2020

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: Andrew Cool 
Summary Author: Andrew Cool 

As shown above at top, stars aren’t always crystal clear on all-sky or fisheye imagery. While software can be written to convert fisheye images to equirectilinear format (altitude-azimuth system of coordinates), this results in unwanted distortion. To counteract this distortion, I’ve written new software to create a model 3D Hemisphere, over which I drape the equirectilinear image so that a 180-degree sky map is mapped onto a hemisphere image. This essentially reverses the distortion and produces a 3D sky with crisp, pinprick stars (bottom image). With new software development, such as described here, it's now possible to see the sky as represented on fisheye photos in correct proportions. For me, all-sky dewarping efforts derive from my interest in measuring light pollution for the River Murray International Dark Sky Reserve in South Australia.