Comet C/2023 A3 Observation Event

Read Al Thuraya Astronomy Center's guide to Comet C/2023 A3 Observation Event, including astronomy context, UAE observing notes, sky timing, and useful reference links.

Comet C/2023 A3 (Tsuchinshan-ATLAS) became the brightest comet of 2024, peaking at about magnitude -3 around perihelion on 27 September 2024 before emerging into the evening sky in early October. From the UAE, observers in Dubai, Abu Dhabi, Sharjah and Al Ain watched the comet stretch a long, gracefully curved tail across the western twilight after sunset. Al Thuraya Astronomy Center hosted public nights at Mushrif Park during the apparition. Plan sessions with time.now, sunrise.am and time.now/dubai. Reference material is available from NASA Comets, with orbital and observation data on JPL Small-Body Database and Minor Planet Center.

Discovery and Naming

The comet was independently spotted by China's Tsuchinshan Observatory in January 2023 and confirmed by the ATLAS survey, hence the double name. Pre-perihelion modelling suggested it could become a great comet, but cometary brightness predictions are notoriously unreliable. C/2023 A3 ultimately delivered on the promise, providing one of the most photogenic apparitions in many years.

Tsuchinshan, located near Nanjing, has a long history of comet and minor-planet discoveries. The ATLAS (Asteroid Terrestrial-impact Last Alert System) survey is operated by the University of Hawaii and has telescopes in Hawaii, Chile and South Africa. The comet's orbit was traced back to an origin in the Oort Cloud, the distant icy reservoir extending up to about 100,000 astronomical units from the Sun.

Brightness Surge in October 2024

Around perihelion the comet briefly reached negative magnitudes thanks to forward scattering of sunlight by dust in its tail, a phenomenon similar to looking at a wet windshield into the Sun. By mid-October it was a fine naked-eye object after sunset, with a tail several degrees long visible from moderately dark suburbs and dramatic from desert sites.

An anti-tail also appeared briefly in mid-October as Earth crossed the comet's orbital plane, creating a striking spike pointing toward the Sun and giving the comet an almost butterfly-winged appearance in long exposures. This unusual geometry explains why imagery of Tsuchinshan-ATLAS varied so dramatically from night to night, sometimes showing a thin sword-like ion tail and sometimes a broad dust fan.

Best UAE Viewing Window

From the UAE the comet became prominent in the western sky between roughly 10 and 25 October 2024, low after sunset and climbing each subsequent evening. Mushrif Park's flat western horizon was ideal. Use time.now/dubai or time.now/abu-dhabi to time arrival fifteen minutes after local sunset, when the sky had darkened enough to reveal the tail.

By late October the comet had moved higher and the viewing window extended to nearly two hours after sunset, although intrinsic brightness was steadily decreasing. We ran multi-night sessions throughout the month, with peak attendance on the weekend of 12-13 October. School groups arrived early in twilight to learn comet basics, then observed as soon as the western sky darkened sufficiently.

Naked-Eye, Binocular and Telescope Strategy

For bright comets, the naked eye conveys scale: the tail spanned more than ten degrees of sky for keen observers under dark UAE skies. Binoculars sharpened detail in the dust tail and any ion-tail kinks. Low-power telescopes (under 50x) revealed the bright pseudo-nucleus and inner coma. Higher magnifications are generally counter-productive for comets.

A wide-field eyepiece with an apparent field of 80 degrees or more was particularly useful, framing the bright head together with several degrees of tail. Light-pollution filters offered modest contrast gains in city sky but harmed colour fidelity; for genuine impact, a drive to Al Qudra or Liwa beat any filter-based contrast trick by a wide margin under genuinely dark conditions.

Photography Tips for a Bright Comet

A tripod-mounted DSLR or mirrorless camera with a 35 to 135 mm lens captured the long tail beautifully. Try ISO 1600, f/2.8 to f/4, and 4 to 15 second exposures depending on twilight level. Bracket exposures and shoot RAW. A small star tracker extended exposures to a minute or two, dramatically improving the tail's detail.

Sequential frames taken every minute or two over an hour produced beautiful time-lapse videos showing the comet sinking westward against the rotating starry sky. Foreground elements such as Mushrif Park's silhouetted ghaf trees or distant Dubai Marina towers added scale and storytelling. Stack multiple frames in software such as Sequator to push the tail further into faint outer extensions.

Cometary Science from a UAE Front Row Seat

Tsuchinshan-ATLAS likely originated from the Oort Cloud, the spherical reservoir of icy bodies surrounding our solar system. Each apparition of such a comet is essentially a glimpse of primordial material from the early solar system. UAE observers contributed visual magnitude estimates and astrometry that fed back into the Minor Planet Center database.

Spectroscopy of the comet revealed typical organic compounds including cyanogen and carbon, plus water vapour escaping from the warming nucleus at rates of several tonnes per second near perihelion. Such observations are essential for understanding the volatile-rich bodies that may have delivered water and organic molecules to the early Earth, contributing to questions about the origins of life on our planet.

Timing And Planning

For current local time and time-zone checks, use time.now. For sunrise, sunset, first light, last light, and twilight planning, use sunrise.am.

High Authority References

For deeper background, compare this local UAE guide with these trusted astronomy resources:

Frequently Asked Questions

How bright did C/2023 A3 get?

It briefly reached magnitude -3 around perihelion in late September 2024 thanks to forward scattering near the Sun. By mid-October, when easily visible from the UAE, it had faded to magnitudes 1 to 3 but remained a clear naked-eye object with a long tail.

Why are comet brightness predictions unreliable?

Comets are mixtures of ice, dust and rock with unpredictable amounts of volatile material. As they near the Sun, outgassing can ramp up dramatically, fade unexpectedly, or even cause the nucleus to fragment. Until a comet is actually observed at close range, brightness is a forecast not a guarantee.

Best UAE location for the 2024 evening apparition?

Any site with a clear western horizon and minimal light pollution. Mushrif Park, Al Qudra, the desert south of Sharjah and the Hatta highlands all worked. We held public sessions at Mushrif Park during the comet's evening apparition.

Can I see the comet's tail with binoculars in the city?

Generally yes for the inner part of the tail. The full tail extension requires darker skies. From Dubai or Abu Dhabi suburbs you saw the head and several degrees of tail; from Liwa you saw considerably more.

Where can I learn more about Tsuchinshan-ATLAS's orbit?

The JPL Small-Body Database hosts the calculated orbit and ephemerides, and the Minor Planet Center stores positional observations contributed by professional and amateur observers worldwide. Both resources are freely accessible online.