It’s time to grab a last look at the comet while you still can. It’s been an excellent week for comet-spotters, with the tail of comet Tsuchinshan-ATLAS (also called C/2023 A3 and Comet A3) brightening earlier in the week.
It’s now fading as it speeds away from the inner solar system, rising quickly into the night sky. It’s also now past it best in terms of brightness, but it this weekend is still a great time grab a glimpse. You’ll need binoculars and patience to see it, particularly from urban areas with light-polluted skies. If you find it, here’s how to photograph it.
Tonight, Saturday, Oct. 19, is the ideal time to look for the comet from the northern hemisphere — because it will be visible against a darker, moonless sky — but you’ll likely need to observe from somewhere that looks dark on a light pollution map or from a Dark Sky Place.
Here’s exactly when and where you need to look to see the comet on Saturday, Oct. 19.
Note: times and viewing instructions are for observers at mid-latitudes in the Northern Hemisphere. Check the exact time of sunset where you are and the comet’s setting times on Stellarium Web for times accurate for your exact location.
How To Locate Comet Tsuchinshan-ATLAS: Saturday, Oct. 19
Position: west, 42 degrees from the sun in Ophiuchus
Time: 45 minutes after sunset where you are
Magnitude: +1.75
Comet’s distance from the sun: 64.6 million miles (104 million kilometers)
Comet’s distance from Earth: 54.4 million miles (87.6 million kilometers)
This evening, the comet will be visible high above the western horizon about 45 minutes after sunset, setting around two hours 35 minutes later. That means it will be in the sky for about 10 minutes longer than on Friday. However, you may need to use a pair of binoculars to find it.
Find the bright planet Venus above the southwest and the bright star Arcturus above west-northwest. Now make a third point of the triangle high above — that’s where the comet is. If Venus isn’t visible, use nearby Antares, another red supergiant star.
As a bonus sight, a few hours after sunset a bright waning gibbous moon will rise in the east just below the Pleiades, a sparkling open cluster of stars that are always a spectacular sight to both the naked eye and binoculars.
What Is Comet Tsuchinshan-ATLAS?
It’s a long-period comet from the Oort Cloud, which is a sphere around our solar system that’s home to millions of comets. It loops around the sun only once every 80,000 years.
Comet Tsuchinshan-ATLAS was discovered in January 2023 by astronomers at China’s Tsuchinshan (Purple Mountain) Observatory and South Africa’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope.
How Long Can You See The Comet For?
We’ve been lucky with comet Tsuchinshan-ATLAS. It’s been visible to the naked eye until now, but around now — Saturday, Oct. 19 or Sunday, Oct. 20 — it will begin to fade quickly. So much so that you shouldn’t expect to see it with the naked eye again.
According to Sky & Telescope, you won’t see it with the naked eye on Halloween — Oct. 31. However, it will likely remain visible through binoculars until early November.
Check my feed every day this week and next for a daily “comet tracker” with sky-charts and tips for viewing the comet.
Wishing you clear skies and wide eyes.
