A few minutes after local sunset (1751 MST) on Sunday, 13 October 2024, I went outside to begin my Comet Tsuchinshan-ATLAS (C/2023 A3) observing session.

1829 MST: Spotted the comet in the bright twilight sky using 7x50 binoculars.

1835 MST: The comet was now faintly visible to the naked eye.

1842 MST: Using the binoculars, the comet's tail appeared about 5° long.

1850 MST: As the sky darkened, the tail appeared about 10° long to the eye.

1915 MST: With the comet getting low in the western sky, I ended my comet observing.

These photographs are shown in chronological order. To the eye the comet was much fainter than these long exposure photographs.

1838 MST: D850 DSLR (f/5.6, 2 seconds, ISO 800, FL 70mm)


1845 MST: D850 DSLR (f/5.6, 2 seconds, ISO 1600, FL 70mm)


1847 MST: iPhone 15 Pro Max (3 seconds, 2X lens, slight horizontal crop) - ANTI-TAIL!


1849 MST: iPhone 15 Pro Max (10 seconds, 5X lens) - ANTI-TAIL!


1851 MST: D850 DSLR (f/5.6, 2 seconds, ISO 3200, FL 70mm) - ANTI-TAIL!


1856 MST: D850 DSLR (f/5.6, 2 seconds, ISO 6400, FL 70mm) - ANTI-TAIL!


1901 MST: iPhone 15 Pro Max (10 seconds, 2X lens, slight horizontal crop) - ANTI-TAIL!


1904 MST: D850 DSLR (f/5.6, 4 seconds, ISO 6400, FL 92mm) - ANTI-TAIL!


1907 MST: iPhone 15 Pro Max (10 seconds, 2X lens, slight horizontal crop) - ANTI-TAIL!


1913 MST: D850 DSLR (f/5.6, 4 seconds, ISO 6400, FL 92mm) - ANTI-TAIL!

It was exciting to capture the comet's anti-tail and to have it appear so bright (photographically). A comet's anti-tail is an optical illusion (of the dust tail) and appears only during a brief period when the comet passes through the plane of the Earth's orbit around the Sun.

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