First Night of Comet A3

Starlog October16th, 2024, 7:25 p.m. local time

It has been over four years since I last photographed a comet. Tonight I saw and photographed the current star (no pun intended) of 2024, Comet C/2023 A3, a.k.a. Tsuchinshan-ATLAS, a.k.a. Comet A3.

I consulted both the Heads UP! and How I See It blogs for information on A3, so a shout-out to both of their authors.

Most guides online say to use the planet Venus and the star Arcturus to find Comet A3 between them. The problem with this for me was that it was nearly impossible to find Venus 45 minutes after Sunset due to obstructions in my neighborhood. But using binoculars, I was able to locate A3’s head and a good portion of its tail.

With my Sigma 50mm wide lens and Canon EOS Rebel SL3, I captured A3 and the surrounding stars:

If you notice above A3, there is a triangle of stars. I used them as a guide in my binocular search and later aim of my camera. Here is the same image with those stars circled:

Even though A3 will “move” each night, I will still use these stars as guides when the comet ascends into the West sky each night. I like to know which stars I am looking at, so as I have done many times before, I consulted Stellarium. Note that Arcturus was off to the right in this image and Venus away past the left and nearly at the horizon.

Here is the view from Stellarium for the same time period:

To more easily relate the above Stellarium screenshot with my photograph, here are the three triangle stars circled:

Don’t ask me to pronounce this, but Unukalhai is a magnitude 2.8 double star, easily seen even in my heavily light-polluted skies.

I took this article’s header image with my 300mm stock lens.

Weather permitting, I will attempt to view and photograph Comet A3 for the next several days.

Equipment Used (article header image):

• Canon EOS Rebel SL3
• 300mm lens, 105mm focal length
• f/4.5
• 0.8 sec exposure
• ISO 1600
• Touchups in PaintShop Pro and AfterShot Pro

Equipment Used (in-article wide image):

• Canon EOS Rebel SL3
• Sigma wide field lens, 50mm focal length
• f/2.8
• 0.8 sec exposure
• ISO 1600
• Touchups in PaintShop Pro and AfterShot Pro