If you’ve not seen comet Tsuchinshan-ATLAS yet, it’s not too late, but be quick! Long past being a bright, naked-eye object after sunset, comet A3 (also called C/2023 A3) is now a binocular object.
However, while it was somewhat hard to find in the bluish twilight, the comet is now shining against a black sky for a few hours after sunset.
As a bonus, it’s relatively easy to find below the famous “Summer Triangle” asterism of three bright stars. If you’re quick, you can even use Venus as a signpost to find it soon after sunset.
With solar activity spiking this week, there’s even a possibility of the comet being in the sky at the same time as the Northern Lights start to dance. But maybe that’s a long shot.
See below for two different ways of finding comet Tsuchinshan-ATLAS (also called comet A3 and C/2023 A3).
Where Is Comet Tsuchinshan-ATLAS?
Now 84 million miles (135 million kilometers) from Earth and shining at a magnitude of +3.8, the comet remains technically visible to the naked eye, but you’d need to be away from light pollution for a chance.
Either way, it’s rapidly getting fainter and smaller, and to get any kind of impressive view will require a pair of binoculars or a small telescope. Another way to see it is to photograph the comet with a camera or a smartphone because a long exposure image of a few seconds will show it more easily.
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 that are accurate for your exact location.
How To Locate Comet Tsuchinshan-ATLAS: Tuesday, Oct. 29
Position: west, 55 degrees from the sun in Ophiuchus
Time: from 60 minutes after sunset until about 22:30 local time
Magnitude: +3.8
Comet’s distance from the sun: 82 million miles (132 million kilometers)
Comet’s distance from Earth: 84 million miles (135 million kilometers)
How To Find The Comet Using Venus
If you look southwest about an hour after sunset, you’ll likely see the bright planet Venus. That’s your guiding light to the comet.
Look above Venus for the bright star Vega in the constellation Lyra. Look halfway between Venus and Vega, and you should find the comet, though probably only if you use a pair of binoculars.
How To Find The Comet Using The Summer Triangle
Since Venus will sink soon after sunset — or you may have horizon clouds or mountains to contend with — you can also use the stars of the Summer Triangle, of which Vega is one. Find the other two that make up the famous asterism — Deneb in Cygnus, above Vega, and Altair in Aquila, to the left.
Now, make a rough triangle between Altair and Vega by pointing down to the horizon. The third point is roughly where the comet will be. You’ll need binoculars to see it — as well as a dark, clear sky.
What Is Comet Tsuchinshan-ATLAS?
It’s a long-period comet from the Oort Cloud, a sphere around the solar system that’s home to millions of comets. Astronomers think it loops around the sun once every 80,000 years. Its coma is about 130,000 miles (209,000 kilometers) in diameter, and its tail extends around 18 million miles (29 million kilometers) into space.
Check my feed for a daily “comet tracker,” with useful sky charts and tips for viewing the comet.
Wishing you clear skies and wide eyes.