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    Re: Milky Way photo navigation challenge
    From: Russell D. Sampson
    Date: 2021 Jun 27, 12:46 -0700


    Thanks for including me. 

    It took some mental gymnastics to orient the constellations - Sagittarius top center - Corona Australis got me there.  The most likely date appears to be - June 13, 2018 - since just north of the teapot lid and very close to the ecliptic is a bright extra star - a planet.  Considering the darkness of the sky I eliminated the inferior planets. Considering the colorlessness of the planet, I eliminated Mars.  Consider the relative brightness of the planet (approx. vis magnitude 1.0 to 0.0) I eliminated Jupiter (and Venus) ... leaving Saturn.  Now going to my planetarium software I time-zoomed Saturn and ... bingo ... June 13, 2018.   The match is almost perfect, with the planet lining up very nicely with the stars HC90513 and 21 Sgr.  

    Now the location.  I have never seen the teapot of Sgr tipping like that from Connecticut.  So, south we go.  Since the faint clouds in the bottom part of the sky are all oriented horizontally, I concluded that the image was not rotated 90-degrees with respect to the terrestrial part of the photo collage.  Since the clouds were also confined to the bottom part of the image I also assumed (a little less confidently) that the image was not rotated 180-degrees.  Assuming a uniform distribution of clouds there will always appear to be more clouds near the horizon than near the zenith - same reason you see fewer trees in the forest looking straight up, and fewer stars near the galactic poles.  

    Now, playing with the computer simulated sky on June 13, 2018 I got a reasonable orientation when travelling south to about 0-5S latitude and at a time of about 4:00 AM local time, looking towards the SW (center of sky image azimuth about 225 degrees and altitude about 30 degrees - not the orientation of the lighthouse).  The apparent diurnal motion in the bottom right of the sky, appears to be lens aberration - coma.  To reduce that, the photographer needs to stop down the lens, or buy a better lens.  The absence of coma in the top left of the frame suggests the photographer cropped the sky image - most likely to better center the Milky Way with respect to the lighthouse.

    By the way, if the lighthouse is a government run facility, there is evidence that the image was taken during the day ... the flag is still flying.  Day-for-night, a trick used by cash-strapped cinematographers - underexpose and hope for clouds.  



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