Where and when to see it this weekend

What time will comet A3 be visible today and tomorrow? Comet A3, also known as Comet Tsuchinshan-ATLAS (C/2023 A3), is now putting on a show for those in the northern hemisphere.

It shines at about +4 magnitude, first in the east before sunrise in late September and then in the west after sunset in mid-October. Comet A3 has two tails, like most comets—a blue plasma tail of ionized gas and a white dust tail of dust, rock, and frozen gas.

With good planning, clear weather and timely observation, Comet A3 and its bright tail should make for a spectacular sight this late September. and in Oct. Here’s how you can see Comet A3 this weekend.

Check out my feed every day this week and next for a daily “comet tracker” with sky maps and tips for viewing Comet A3.

Where to see Comet A3: Saturday, September 28

Position: east-southeast, 22.5 degrees from the sun in Sextans

Time: one hour before sunrise where you are (around 07:00 in the US)

Expected size: +4.5

Comet distance from the sun: 58.6 million kilometers

Comet distance from Earth: 131.5 million kilometers

This morning, Comet A3 will be just one day past perihelionso it should be relatively bright, though low on the horizon. It should become visible—tail first—just above the east-southeast about 75 minutes before sunrise, and will be best seen in astronomical darkness, which lasts until about 60 minutes before sunrise. That’s a 15 minute window!

Where to see Comet A3: Sunday, September 29

Position: east-southeast, 22.3 degrees from the sun in Leo

Time: one hour before sunrise where you are (around 07:00 in the US)

Expected size: +4.5

Comet distance from the sun: 58.9 million kilometers

Comet distance from Earth: 124.9 million kilometers

This morning, Comet A3 will be visible a little closer to the east-southeast an hour before sunrise. It will be placed below a 9% waning crescent moon and Regulus, the brightest star in the constellation Leo.

Like yesterday, it should be visible just above the east-southeast about 75 minutes before sunrise and will be best seen in astronomical darkness, which will last until about 60 minutes before sunrise. Another small window.

When to see Comet A3 in October 2024

Comet A3 will dip into the sun’s glare soon (around October 2), but will re-emerge at dusk around October 12 for those in the Northern Hemisphere.

This is the most convenient time to see Comet A3. Look west just after sunset to see it possibly at its brightest and best, although in the evenings after October 12, it will climb higher in the sky.

I wish you clear skies and open eyes.