Comet C/2023 A3 (Tsuchinshan–ATLAS)

Comet Tsuchinshan–ATLAS, officially designated C/2023 A3, is a long-period comet originating from the Oort Cloud. It was discovered in early 2023 by China’s Purple Mountain Observatory and the ATLAS survey in South Africa, which gave the comet its name. It became bright enough to see without a telescope, reaching its peak brightness in early October 2024.

October weather in our region is usually far from ideal for astronomy, yet there were a few clear nights that allowed me to observe this remarkable comet. Still, as captivating as the sight of a celestial visitor may be, most of my visual sessions quickly turn into astrophotography. That was the case on October 20, 2024: after a short look at the comet through my Stellarvue SV102ED refractor on a GSO ATZ (Astro-Tech Voyager) mount from the balcony, I switched to imaging. Ideally, I would have used an equatorial mount for proper tracking, but with no time to set it up, I simply attached my Nikon D5100 to the telescope and began shooting with very short exposures, occasionally nudging the alt-az mount to keep the comet in view. Before it disappeared behind the buildings opposite, I managed to capture 557 frames at 0.5 second each, ISO 10000. The final result is a composite stack of both the stars and the comet.

Despite the challenges, watching Comet Tsuchinshan–ATLAS from my balcony felt truly special. The October air was chilly, the city lights lit up the sky, yet the comet stood out clearly — a small but distinct traveler against the stars, with bright core and a hint of a tail. 

Aiming the telescope by hand during imaging was a bit of a struggle, and exposures had to be kept short, but that only added to the sense of capturing something fleeting. The final stacked image brought out details too faint to see with the naked eye: a brilliant core and a tail displayed in all their beauty. Using a Rotational Gradient algorithm, I was also able to enhance the fine structures in the inner coma, bringing out delicate features otherwise hidden. 

When the next bright comet appears in the sky, I hope to give it the full treatment on an equatorial mount, but even this improvised session turned into a rewarding memory of a rare visitor from the edge of the Solar System.