How to Photograph a Comet

Home » Photography Tutorials » Astrophotography » How to Photograph a Comet

You’ve probably heard or read about a comet that might become extremely bright in the night sky this October, and that it might reach naked-eye visibility, giving you a great opportunity to learn how to photograph a comet!

The comet that might become visible is Comet Tsuchinshan-ATLAS. Whether you’ve seen this comet or you’re interested in capturing future comet displays, let’s delve into the fascinating world of comets and learn how to photograph them.

Understanding comets

Comet Tsuchinshan-ATLAS is one of the latest cosmic travellers to captivate astronomers and stargazers alike.

Officially designated C/2023 A3 (Tsuchinshan-ATLAS), the comet was first spotted at the beginning of 2023 by two independent observatories: the Tsuchinshan Observatory in China and the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey in South Africa.

Early observations suggest that the comet could put on a spectacular show, with some predictions comparing its potential brightness to famous comets like Hale-Bopp or NEOWISE. But, of course, comets are like cats: they have tails and do whatever they want.

Let’s hope the predictions are true, and we will see a Great Comet.

Throughout history, comets have been both feared and revered. In ancient times, they were often seen as omens, signalling the arrival of important events or disasters. The appearance of Halley’s Comet in 1066 was famously recorded in the Bayeux Tapestry, which depicts the Norman conquest of England.

In more modern times, comets have become symbols of scientific curiosity and discovery, as astronomers continue to unlock the mysteries of these icy wanderers.

Comets are icy bodies that usually orbit the Sun in highly elliptical paths. They originate from two main regions in the Solar System: the Kuiper Belt and the Oort Cloud. They are composed of a mix of water ice, frozen gases, dust, and rocky material.

When a comet is far from the Sun, it remains relatively inactive, appearing as a small, frozen object. However, as it approaches the Sun, the heat causes its ices to sublimate, turning from a solid directly into a gas.

This process forms a glowing cloud of gas and dust around the comet’s nucleus, known as the coma.

The interaction between the solar wind and the comet’s coma creates the characteristic tail that comets are known for. In fact, comets can have two tails: a gas tail (or ion tail) and a dust tail.

The gas tail is made of ionized particles that are pushed away from the Sun by the solar wind, while the dust tail consists of small dust particles that reflect sunlight, making it visible to the naked eye. These tails can stretch for millions of kilometers, creating a breathtaking sight in the sky.

These characteristics make comets visually striking and, therefore, excellent subjects for photography.

After reaching its closest point to the Sun, called perihelion, the comet will begin to move away from the Sun, gradually losing its brightness and returning to a more dormant state.

Some comets may disintegrate entirely after repeated passes near the Sun, while others may continue to orbit for many centuries or millennia. Others may never return.

By studying comets, researchers can gain insight into the conditions that existed during the Solar System’s formation.

Cometary material may hold clues about the origins of water on Earth, as it is believed that comets may have delivered water to our planet during its early history. Additionally, comets may have played a role in the delivery of organic compounds, which are the building blocks of life.

In recent decades, spacecraft missions have provided us with up-close views of comets. The European Space Agency’s Rosetta mission to Comet 67P/Churyumov–Gerasimenko was a groundbreaking effort that allowed scientists to study a comet in unprecedented detail.

The spacecraft orbited the comet and even deployed a lander, Philae, onto the comet’s surface.

How to photograph comets

Comet photography is a fascinating branch of astrophotography, offering a rare chance to document one of the most awe-inspiring phenomena in the night sky. Their unpredictable appearances can make them both a challenge and a delight to photograph.

Comets are probably my favourite astronomical objects, and I enjoy observing and photographing them.

Comets are typically visible for short periods, and some may only appear once in a lifetime, like the famous Halley’s Comet. Others, like Comet NEOWISE or Hale-Bopp, may surprise us with sudden appearances and linger for a few weeks or months.

Due to their transient nature, planning and preparation are key to successful comet photography.

Equipment needed for comet photography

Let’s begin by looking at what gear you will need.

1. Camera body

While almost any camera can capture a comet if conditions are right, a DSLR or mirrorless camera is highly recommended for capturing detailed, high-quality images.

These cameras offer full manual control, large sensors, and the ability to swap lenses, all of which are essential for astrophotography.

If you don’t have a DSLR or mirrorless camera, don’t be discouraged. Some modern smartphones with advanced cameras can capture decent comet images (if the comets are bright), especially when paired with apps that allow manual exposure adjustments.

However, for the best results, a DSLR or mirrorless camera is the preferred choice. You will not need a camera modified for astrophotography to take amazing photos of comets.

2. Lenses

When selecting a lens for comet photography, consider two options:

Wide-angle lenses: These lenses are useful for capturing the comet in a broader context, perhaps against a landscape or a cityscape. A lens with a focal length between 24mm and 35mm will allow you to compose beautiful, sweeping images of the sky with the comet as part of the scenery. If a comet is exceptionally spectacular, you might try even wider focal lengths.

Telephoto lenses: For close-up shots of the comet’s nucleus and tail, telephoto lenses are ideal. A lens with a focal length of 200mm or more will magnify the comet and help isolate it from the surrounding stars. Longer focal lengths of 400mm or higher will reveal even more detail, such as the comet’s coma structure and the subtle hues of its tail. You can also use telescopes, of course.

3. Tripod

A sturdy tripod is essential for comet photography due to the long exposure times required. Even the slightest movement during the exposure can ruin your shot. Make sure the tripod is steady and positioned on a firm surface to prevent any vibration.

4. Remote shutter release or intervalometer

To minimize camera shake, use a remote shutter release or intervalometer.

These tools allow you to trigger the shutter without physically touching the camera, ensuring your images are sharp and free of blur. Some modern cameras also have smartphone apps that enable remote control.

5. Star tracker (optional)

For more advanced comet photography, consider using a star tracker. A star tracker is a motorized mount that moves in sync with the rotation of the Earth, allowing your camera to take longer exposures without the stars or the comet appearing as streaks.

This tool is particularly useful for photographing faint comets or capturing the fine details in a comet’s tail and coma.

Planning for comet photography

Now that your gear is ready, here are top tips to help you plan your comet photography.

1. Find the comet

The first step in photographing a comet is finding out when and where it will be visible. Comets are usually announced by astronomers months or weeks in advance, and you can track their position using astronomy apps like SkySafari, Stellarium, or Heavens-Above.

These apps will provide real-time information on the comet’s location, visibility, and brightness.

Some comets are visible to the naked eye, but most of them are too faint and require binoculars or telescopes to locate. Make sure to research when the comet will be brightest, as this is the best time for photography.

The visibility of a comet also depends on your geographical location, so plan accordingly. Don’t expect all comets to be spectacular and develop a beautiful tail. Most of them will appear as greenish or gray blobs, barely visible even through a powerful telescope.

Here’s a map that shows the position of Comet Tsuchinshan-ATLAS in the evening sky between October 11 and 20. The map was plotted for the latitude of Paris but can be used throughout the northern hemisphere.

If you are south of Paris, you will have better conditions to see the comet, while it will be worse if you are farther north.

2. Choose the right location

To capture the best images of a comet, you’ll want to shoot from a dark location, far away from city lights and light pollution. Light pollution can obscure the faint details of the comet and limit your ability to capture its full beauty.

National parks, remote rural areas, and dedicated dark-sky reserves are ideal spots for comet photography.

Check the weather forecast before heading out, as clear skies are crucial. Clouds and haze can block your view of the comet, so it’s best to be patient and wait for a night with good conditions.

When comets are very bright, you might be able to photograph them from the city or even during the daytime, however, don’t try to photograph comets during the daytime unless you have extensive experience using your gear.

When comets are visible during the daytime, they are very close to the Sun, so not observing them properly might permanently damage your vision. Always hide the Sun behind a building or another completely opaque object when trying to spot comets near the Sun.

3. Timing is key

Comets are typically more visible during certain times of the night, depending on their position in the sky. Often, the best time to photograph a comet is during twilight, just after sunset or before sunrise, when the sky is dark but the horizon still holds a faint glow.

This allows for more dynamic images, with the comet set against a colourful sky. My advice would be to aim for the time when the Sun is around 15 degrees below the horizon.

In other cases, the comet may be high in the sky during the dead of night, in which case you’ll need to work with a completely dark sky and stars as your backdrop. This usually happens when the comets are faint, and you will need telephoto lenses or telescopes to photograph them.

Camera settings for comet photography

Once you’ve located the comet and set up your camera, it’s time to dial in the settings. The correct settings will vary depending on the brightness of the comet and the ambient light conditions, but the following guidelines should provide a solid starting point.

1. Mode: Manual

Shoot in full manual mode to have complete control over your exposure, aperture, and ISO settings.

Astrophotography requires precise control, and automatic settings won’t give you the flexibility you need.

2. ISO settings

Start with an ISO setting between 800 and 3200. Higher ISO settings increase the camera’s sensitivity to light, but they also introduce noise, which can degrade the quality of the image.

Depending on your camera model, find the highest ISO that provides a good balance between light sensitivity and image quality.

3. Aperture settings

Use a wide aperture (low f/stop number) to allow as much light into the camera as possible. An aperture between f/1.8 and f/2.8 is a good starting point, but you can adjust as necessary depending on the light conditions and the brightness of the comet.

4. Shutter speed

Shutter speed is perhaps the most crucial setting in comet photography. A long exposure allows more light to hit the sensor, which is essential for capturing faint objects like comets.

However, an exposure that is too long can result in the comet or stars appearing as streaks due to the Earth’s rotation. If using an equatorial mount or star tracker, you will not have any problems with stars trailing in your photos.

5. Focus

Focusing on a distant object like a comet can be tricky. Use manual focus and set it to infinity, then fine-tune the focus by using the live-view feature and zooming in on a bright star (don’t use the comet for focusing). Adjust until the stars appear as sharp points of light.

For more details on how to choose exposure times and how to use an equatorial mount, please read the following articles:

One challenge in comet photography is that the comet and stars move at different rates across the sky. During long exposures, this can lead to either blurred stars or a blurred comet, depending on where the camera was focused. In post-processing, you can fix this by using star alignment and comet stacking techniques.

Star alignment: If you have taken multiple exposures, you can use software like PixInsight or Siril to align the stars across your frames.

This ensures that the stars remain sharp and in the same position in each image. Then, you can stack this batch to create the backdrop of stars for your image.

Comet stacking: Once the stars are aligned, you can align and stack the comet. Many specialised astrophotography programs allow you to track the motion of the comet across the frames and stack them independently of the stars.

Some software will automatically merge the image aligned for stars with the one aligned for the comet. Otherwise, you will have to manually do that either in astrophotography software or in Adobe Photoshop.

This technique is highly effective for producing clear, sharp images of both the comet and the stars.

In conclusion

Photographing comets is a rewarding and exciting experience that allows you to capture a fleeting piece of the cosmos.

Remember, patience and practice are key in comet photography—each comet presents a unique challenge, but the results are always worth the effort.

Clear skies!

How to Photograph a Comet

Understanding comets