If you’ve already heard about Comet A3 — destined to become the brightest comet of 2024 and one that may become very bright in mid-October — you likely have a question: how best to photograph it? The first photos are in — and they look spectacular.
If it survives today’s perihelion — when it passes within 58.6 million kilometers of the sun — comet C/2023 A3 Tsuchinshan–ATLAS is now visible to observers in the Northern Hemisphere.
Here’s everything you need to know about how to observe and photograph comet A3.
Check my feed every day this week and next for a daily “comet tracker” with sky-charts and tips for viewing Comet A3.
When To Photograph Comet A3
Comet A3 will be visible close to the horizon, as seen from the Northern Hemisphere, on two separate occasions, but either is good for capturing it above buildings, mountains and trees. Comet A3 will first reach its closest to the sun, then its closest to Earth. Both of these occasions should see it shining brightly.
- Sept. 27: comet A3 will reach its perihelion — the closest it gets to the sun — at about 36 million miles (58 million km). The observing period stretches from Sept. 27 through Oct. 4, but it will likely be relatively dim.
- Oct. 12: comet A3 will reach its closest to Earth at about 44 million miles (71 million km) from Earth. The observing period stretches from Oct. 10 through the end of the month, but this is when it will likely be at its brightest — and possibly extremely bright.
The best tactic is to image it as soon as you can, trying for it from Sept. 27 before sunrise and then from Oct. 12 after sunset.
When To Photograph Comet A3 With A Crescent Moon
As luck would have it, a crescent moon will hang close to Comet A3 on these mornings, which should make for great images:
- Monday, Sept. 30: an hour before sunrise where you are (around 07:00 in the U.S.) when comet A3 will be to the lower-right of a 5%-lit waning crescent moon.
- Tuesday, Oct. 1: an hour before sunrise where you are (around 07:00 in the U.S.) when comet A3 will be to the right of a 1.5%-lit crescent moon.
Images should capture the delicate light of comet A3 and its tail and the moon’s delicate crescent showing subtle “Earthshine” on its dark limb.
When To Photograph Comet A3: What The Pros Say
“I’ve been looking into potentially visible times in the coming weeks in the northern hemisphere; closer to the equator, it may be visible at dawn late September, however, this is very close to sunrise,” writes astrophotographer Ollie Taylor. “A better bet for me, and I believe most people, is mid-October when the comet will be visible in the western sky after astrotwilight for a short period at around 4-8 degrees of elevation, depending on where you are situated.”
Photography Equipment You’ll Need For Comet A3
Unless it’s particularly bright, you’ll need much more than a smartphone for comet A3. The best results will come from using a DSLR or mirrorless camera with manual settings (so you can control aperture, ISO, shutter speed and focus) and interchangeable lenses.
You’ll need a wide-angle lens for an astro-landscape shot that features Comet A3 behind an interesting foreground. You’ll need a zoom lens to capture it closer for a more technical astrophotography image. Many astrophotographers will be using a manual camera attached to a small telescope.
Whatever you consider, a long exposure will be necessary, so always use a tripod.
How To Get A Sharp Image Of Comet A3
Focusing on Comet A3 is tricky since it’s a fuzzy blob, but unless you get a tack-sharp image, the stars in the background will be blurred, and your image will look amateurish. Here are four ways to do that:
- Use autofocus to accurately focus your camera on something in the distance during daylight, then deactivate autofocus and don’t touch your lens (or tape it in place to prevent it from moving).
- Focusing on a star. Using the moon is another. Using live view on your camera, pan across to the star/the moon, get it tightly focused, and then pan back to the comet.
- Use an artificial light, focusing on a light source about 30-40 meters away, and using live view — possibly even with auto-focus — to get your focus nice and tight. Artificial light sources could be a streetlight or a light in a house some distance away.
- Using infinity, focus on your lens, which may or may not be accurate, depending on your lens. Look for the ∞ symbol on the dial.
Experimenting with camera settings is what capturing Comet A3 is all about.
Camera Settings For Comet A3
Experimentation is what manual astrophotography is all about. As a rule of thumb, use a higher ISO and shorter exposure time the more you zoom. It’s also important to realize that settings at dusk will be different from those at night and that exposures will change rapidly as light levels change.
Here are some starting points for capturing Comet A3.
- Use an 18-55mm wide-angle lens at different focal lengths, with long exposures for about 10 to 20 seconds and ISO 1600.
- Use a zoom lens at 75mm and about six seconds of exposure times on ISO from 800-3200.
- Use a 300mm zoom lens and short exposures of 3.2 seconds at ISO 1600
Whatever you use, think about composition; with the comet above, something interesting, such as a building, a tree, or whatever works in your landscape. Be creative.
How To Photograph Comet A3 With A Smartphone
This isn’t easy, and you’ll likely get little more than a novelty image, but with flagship smartphone’s cameras improving with every iteration, you can still try. Use a tripod and a manual app to control the ISO and the shutter speed and take exposures of between 20 and 30 seconds. Focus on a bright star or the moon. Also, try using your smartphone’s “night mode” (or similar), which may produce a usable image. Either way, the tripod is crucial.
Wishing you clear skies and wide eyes.