How to View Comet C/2023 A3 (Tsuchinshan-ATLAS) in 2024

A new comet is going to grace the skies in September and October of 2024! Amateur astronomers and professionals around the world are eagerly anticipating the arrival of C/2023 A3 (Tsuchinshan-ATLAS), a celestial visitor that promises to be a highlight of the year. As it journeys through our solar system, its brightness and visibility could offer a stunning display for stargazers worldwide. The appearance of this comet will be a rare opportunity to witness a comet that could potentially reach naked-eye visibility. Whether you're an experienced astronomer with a high-powered telescope or a casual observer with just your eyes or a pair of binoculars, this comet's passage presents a chance to connect with the cosmos in an exciting way! This article will guide you through the best times and methods to view this potentially spectacular event, provide tips for capturing its beauty, and explore whether C/2023 A3 might join the ranks of the so-called "Great Comets" of history (spoiler alert: it’s unlikely).

Tempering Expectations

The astronomer David H. Levy once wrote, “Comets are like cats; they have tails, and they do precisely what they want.” For those who remember the craze over Comet ISON in 2012, this phrase will ring especially true. Comet ISON, hailed as the "comet of the century" in 2012, promised a dazzling display but ultimately disintegrated as it approached the Sun, leading to widespread disappointment among astronomers and skywatchers. Despite initial high hopes, its breakup left only faint remnants, failing to produce the spectacular show that many had anticipated. There are a few reasons we should temper expectations around C/2023 A3 and why we should avoid falling for some of the media hype that will no doubt hop up over the next few days. First, C/2023 A3 is probably a first-time visitor to the inner solar system. C/2023 A3 came from the Oort Cloud, judging by its orbit, which is a very cold and dynamically stable place. The inner solar system, however, is a much more violent region of the solar system, complete with solar flares, heating, and tidal forces. These factors, combined with C/2023 A3’s relatively small size, make it especially prone to what’s called a “fragmentation” event similar to what happened to ISON.

Second, even if it survives its perihelion approach, it will be difficult to spot in the sky due to its solar elongation. This term refers to the angle between the Sun and the comet as seen from Earth. When a comet has a small solar elongation, it appears close to the Sun in the sky, making it challenging to observe without the Sun's glare interfering. For C/2023 A3 (Tsuchinshan-ATLAS), this means it will only appear at most a couple dozen degrees above the horizon during twilight or dawn for a few days. During this brief window, observers will need to have a clear view of the horizon and might still struggle against the bright twilight sky. As the comet moves away from the Sun, it will gradually dim, making it even harder to spot. Those who remember Comet NEOWISE (C/2020 F3) in 2020 can use that event as a comparison to this comet. Like NEOWISE, which became visible in the twilight sky after sunset or before sunrise, C/2023 A3 will follow a similar pattern. While we can hope for a similar spectacle, the inherent unpredictability of comets means there is no guarantee that C/2023 A3 will be as bright or as easy to observe. Keep your eyes on the news as this comet develops!

Observing The Comet

(An “all-sky” chart of C/2023 A3. Credit: http://astro.vanbuitenen.nl) Click to Enlarge Image

The best viewing dates for C/2023 A3 (Tsuchinshan-ATLAS) are quickly approaching, making now the perfect time to prepare to see it. Throughout the month of August, the comet will begin to increase in apparent magnitude, brightening to around magnitude 7 by the end of the month. While a magnitude of 7 is not exceptionally bright, it will be visible in most amateur telescopes, like an 8” Dobsonian or similar, offering an early glimpse for eager astronomers. September and October are when the prime viewing opportunities begin. By the beginning of September, we should know if C/2023 A3 will survive its close approach to the Sun or if it’ll fragment. The comet will reach its closest approach to the Sun, known as perihelion, on September 27th. Around this time, the comet will first be visible in the morning hours in the eastern horizon, similar to NEOWISE in 2012. Using your favorite planetarium app like Stellarium or SkySafari, you should be able to spot the comet. By mid-September, it may reach a magnitude of +4, making it visible to the naked eye under dark skies and even more impressive through binoculars or a telescope. Between October 6th through October 12th, the comet will slip between us and the Sun, making it lost in the Sun’s glare. The brightness is predicted to peak at around magnitude +3 around this time, although forward scattering may increase the view. However, this peak will be brief, as the comet is expected to rapidly decrease in brightness throughout October and into November. The comet will likely be at its best from October 14th through October 18th, with the comet being visible a few degrees above the western horizon after sunset, similar in altitude to Venus in the sky. Below is a screenshot from the program Stellarium, illustrating an example of how the comet may (emphasis on may) appear that evening. This image should only serve as a reference image, not an expectation of how it will appear in the sky.

Image Credit: Stellarium Click to Enlarge Image

To maximize your chances of seeing C/2023 A3, choosing the right location is critical. Ideally, you want to find a spot with as little light pollution as possible. Rural areas far from city lights offer the best conditions to be able to spot the comet before sunrise or after sunset, as urban light pollution can significantly reduce the visibility of even the brightest comets. National parks, dark sky parks, and remote countryside viewing locations are great choices.

Clear skies are essential for observing C/2023 A3. Cloud cover, fog, or haze can obscure the comet and reduce visibility, so check the weather forecast leading up to your planned observation time. Considering the comet will likely be relatively faint in the sky, even transparent clouds could render the comet invisible in the sky, making your dark sky trip useless. Aim for nights with minimal or no cloud cover to ensure an unobstructed view of the comet. Additionally, consider the phase of the Moon; a new Moon or crescent Moon phase provides the darkest skies, enhancing the visibility of faint objects like comets. A bright full Moon can wash out the night sky and make it difficult to see the comet, so try to schedule your observation sessions around the lunar cycle for optimal conditions. Fortunately, the Moon appears to be in our favor for this comet. When the comet appears at its “best” in the morning sky in the last few days of September, the Moon will be a waning crescent. The two will likely be in relatively close conjunction with each other in fact, which may provide for some unique widefield photographs.

Equipment and Techniques

When observing a comet like C/2023 A3 (Tsuchinshan-ATLAS), it's important to choose equipment with relatively low magnification for several reasons. Comets typically have large, diffuse comas and extended tails, which can stretch across a significant portion of the sky. Using a telescope or binoculars with low magnification provides a wider field of view, allowing you to see the entire comet, including its faint outer regions and sweeping tail. A good binocular to consider is the Celestron 7x50 Cometron Binoculars, designed with comets in mind. These binoculars offer a very wide 7-degree field of view with a generous 50mm aperture, making it great for collecting a lot of light while being easy to handle. You can observe the comet with these binoculars without any concern for a tripod or additional accessories! Below is a rough example of how the comet’s large size will fill up even this binocular’s field of view. Again, please note that this will NOT be representative of the comet’s brightness in your binoculars, as the comet will appear much dimmer even in the best viewing conditions. Rather, this illustration is to give you an idea of the comet’s apparent size in your binoculars.

Image Credit: Stellarium Click to Enlarge Image

If you have a ZWO Seestar S50 Smart Telescope, now is an excellent opportunity to put it to use! This telescope's rapid setup time allows you to get ready quickly and capture the comet before it becomes obscured by the Sun’s glare. The Seestar S50, with its 250mm focal length, may offer impressive views of the comet that can be conveniently observed through your smart device. This focal length strikes a good balance, providing a wide enough field of view to encompass the entire comet, including its tail, while still delivering detailed images. Furthermore, the live stacking feature significantly enhances your observation experience by increasing the signal-to-noise ratio. Stacking allows you to overlay multiple exposures to create a clearer and more detailed image, revealing more of the structure of the comet’s gas and dust tails.

Astrophotographers should take note - comets can be one of the most exciting celestial events to photograph. Your best bet is to use a color camera that you can quickly set up and align before the comet is lost in the sun’s glare. Alt-azimuth mounts with tracking capability should be considered in addition to equatorial mounts, as you’re photographing a moving object, and your exposure time will be limited even with an equatorial mount. A sturdy tripod should also be used, as well as some sort of remote release. For those with a DSLR or mirrorless camera, consider using a lens with a focal length of 100-200mm. Set the camera in “M” mode, giving yourself full control of the camera settings. Find a bright star (or the Moon, especially if only the moon is visible) and manually focus with the DSLR’s live view mode. Then, point to the comet and take anywhere from 15”-30” exposures. Why not longer? Because the comet itself will be moving during your shots and longer exposures are poorly suited for this reason. Take as many as you can before you either lose sight of the comet below the horizon or the comet is lost in the twilight glare. You should be able to stack the images in a program like DeepSkyStacker to reveal a lot of beautiful detail in the comet!

Will C/2023 A3 Be a "Great Comet"?

(A picture of Comet Hale-Bopp in 1997, the last “Great Comet” visible over the Northern Hemisphere) Click to Enlarge Image

As C/2023 A3 comes around the Sun, there’ll be a lot of hype about whether or not it’ll be a “great comet” similar to Comet Hale-Bopp and others. While the excitement is understandable, it is unlikely to achieve the status of a "Great Comet." One of the key factors limiting its potential is its expected magnitude. At its peak, C/2023 A3 is predicted to reach a magnitude of +2, which, while visible to the naked eye under dark skies, is not exceptionally bright, even when factoring in the effects of forward scattering of the comet’s dusty tail. In comparison, Comet NEOWISE, which captivated observers in 2020, reached a peak magnitude of +1 and displayed a magnificent tail visible even from urban areas. We have confidence that while C/2023 A3 may not become a “great” comet, it’ll still be a “good” comet should it not fragment over the next few weeks.

True great comets, such as Comet Hale-Bopp in 1997 and Comet McNaught in 2007, have set a very high bar for the general public with their brilliance and extended visibility. Hale-Bopp, for instance, reached a magnitude of -1 and was visible for an extended period, showcasing a spectacular display with two distinct tails. Similarly, Comet McNaught achieved a staggering magnitude of -5 and was visible even during daylight. These comets not only shone brighter but also remained visible for longer durations, allowing more people to witness them and leave lasting impacts.

Another factor working against C/2023 A3 is its relatively brief window of visibility. The comet will be best observed in late September and early October 2024, with its brightness peaking around early October. Hale-Bopp, for example, was visible for months in the sky. However, this period of peak visibility will be short-lived as the comet will rapidly dim throughout October and November. Additionally, its proximity to the Sun in the sky will pose challenges for observers, as it will be harder to spot against the twilight and dawn skies, making it less accessible for casual stargazers.

Learn More

Interested in diving deeper into the world of astronomy as this comet approaches? Check out our Astronomy Hub for a wealth of articles, guides, local resources for planetariums and observatories near you, and other resources to enhance your stargazing experience.

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Originally published on August 07, 2024.