Discover the Best Focal Length for Astrophotography

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Are you looking to explore the night sky in a whole new way? Astrophotography is the perfect way to do just that! With the right gear and a bit of planning, you can take stunning photos of star clusters, galaxies, and even the Milky Way. In this article, we’ll discuss the best focal lengths for astrophotography, introduce Stellarium for previsualizing and planning, and discuss the camera lenses and telescopes that will help you capture the perfect shot. So grab your gear and get ready to explore the cosmos!

Use Stellarium to Previsualize the Shot

Before we discuss the best focal length of astrophotography, I strongly recommend Stellarium (a free and powerful planetarium) for you. This program is perfect for visualizing and planning your night sky photo shoot. It shows a realistic sky in 3D and has an FOV (field of view) indicator which allows you to view the field of view of specific equipment.

Interface of Stellarium

What’s more, the very realistic nighttime view can be optimized based on your location to show you the view of the sky with the locations of the stars and the other planets in the Solar System. It has the most extensive collection of stars and locations compared to any other app.

The best thing about this software is that it’s available on your favorite mobile platform and a desktop version. That means you can carry a copy of the software on your field trips, making tracking and composing your Milky Way shots easier.

As you can see from the screenshot of Stellarium, the FOV indicator is located to the left of the bottom. It help orient yourself in the sky and tell you what the current field of view is. You can then convert this data to the focal length. That way you know what kind of sky picture you can get with a lens of that focal length.

Here’s a table of FOV of common lens focal length for the full-frame sensor:

Focal Length (mm)Horizontal FOVVertical FOV

For other sensors, you can refer to this Field of View Calculator. You can also use the Oculars plugin Stellarium and input your camera and lens information to get an accurate depiction of what the target will look like relative to the focal length. Here’s the step-by-step guide on how to use the plugin.

Now we have set the scene, let discuss the various focal lengths used in astrophotography.


This focal length is perfect for milky way shots. It allow greater coverage of that nice beautiful galaxy core or other nebulae to be captured in a single image. Ultra wide angle lenses give your astrophotography a stunning perspective with a great sense of depth as stars, dust and gas clouds in the Milky Way seem to be further away, especially if you keep an appropriate foreground in the frame.

Wider focal lengths are necessary to capture a lot of light in a short time frame. If the exposure is delayed by several seconds, which is normal when using a small aperture lens, the Earth’s rotation brings about star trails that are not desirable.

It is generally recommended to avoid star trailing in astrophotography as these streaks could blur the details of the Milky Way and reduce the clarity of the shot. The longer the exposure, the bigger the streaks would be.

Star Trails

Ideally, it would help if you had a fast aperture lens to freeze the moment by using the fastest shutter speed possible. However as a beginner it’s okay to have a modest amount of star trails your first time because you may have to upgrade your lens.


The 14mm has a generous viewing angle. It is one of the most exhaustive focal lengths for the full-frame camera system.

Approximate Equivalent Focal Length of 14mm in Stellarium

The 14mm has a generous viewing angle. It is one of the most exhaustive focal lengths for the full-frame camera system. Samyang makes a fantastic 14mm prime, the Samyang XP 14mm f/2.4. It is rated as one of the best lenses for astrophotography. This lens has superb image quality and significantly less distortion, if any at all. The build quality is also exceptional, and the lens handles very well. However, one thing to note is that this lens does not come with weather sealing; therefore, if you expose this lens to inclement weather, you must be very careful. That being said, astrophotography is rarely done on bad weather days. If you’re shooting astrophotography, the day has to be clear and dry. On those days, you will have no problems using this lens.

Another exceptional lens is the Sigma 14mm, f/1.8 Art. This lens has excellent sharpness and good separation of chromatic aberrations and distortions, and a 14mm lens captures a wider slice of the night sky. The fast f/1.8 aperture captures a lot of light and helps freeze the moment to capture compelling compositions of the night sky.


The 18mm is yet another focal length perfectly suitable for astrophotography. One of the best lenses in this segment is the Zeiss Milvus 18mm f/2.8 ZF.2. This lens, too, captures a wider slice of the night sky. The lens has near-perfect sharpness with exceptional suppression of aberrations and distortions. This particular lens has been redesigned with a new optical design. The f/2.8 aperture is smaller than the f/1.8 Sigma Art series lens I mentioned above. However, this lens produces decent results compared to the other lens.


The 20mm is a wide-angle focal length. Although not in the same range as the 14mm, this is still a reasonably wide lens for shooting wide panoramic astrophotography images. One of the best lenses under this segment is the Sigma 20mm f/1.4 DG HSM Art.

This has a maximum aperture of f/1.4. It captures a lot of light in low-light conditions. Being an Art series lens, this is a very well-built optical tool. The lens offers excellent sharpness at the center of the frame. However, corners are soft, especially when a wide-open aperture is used. Stopping down the lens helps improve corner sharpness. The lens incorporates several elements that help suppress chromatic and other aberrations and distortions.

Approximate Equivalent Focal Length of 20mm in Stellarium
20mm Real World Milky Way


The 16-35mm lens is an excellent tool for shooting astrophotography. This lens offers a wide focal length range, and most of the lenses under this category offer a fast wide-open aperture. The Canon EF version, for example, comes with a fast aperture of f/2.8.

The lens is designed for the full-frame camera system. The lens features two large-diameter glass-molded dual-surface aspherical elements and one aspherical ground element to suppress spherical aberrations. Sigma also has a lens almost reaching the same focal length as the 18-35mm f/1.8 DC HSM Art. This lens has a slightly smaller focal length at the wide end. But overall, this is also an excellent lens to work with. The lens offers a maximum aperture of f/1.8 that’s constant across the focal length. However, this lens is designed for Canon’s APS-C sensor-powered cameras. The effective focal length will become 28.8-56mm when mounted on an APS-C camera.

The lens features a bunch of special low-dispersion SLD elements that help suppress the effects of color fringing and chromatic abbreviations. Also, the presence of a bunch of aspherical elements ensures that the lens can counter the effects of spherical parts.

The Sony FE 16-35mm f/2.8 GM is a fantastic lens for shooting exciting astrophotography images. The lens comes with a fixed aperture of f/2.8 across the focal length. Designed for the full-frame Sony E mount mirrorless camera systems, this is a Sony Grandmaster lens with the exceptional build quality and promises excellent optical performance.

This lens comes with two extra-low dispersion elements and three aspherical elements. Along with that, the lens also has two XA elements. The most important thing is that this is one of Sony’s Grandmaster series lenses and these lenses have exceptional sharpness that’s ideally suitable for astrophotography purposes.


The 35-85mm focal length range provides enough flexibility to capture a wide variety of constellations and asterisms in a single frame. You can capture constellations such as Orion, Taurus, Ursa Major, and Leo in the Northern Hemisphere. In the Southern Hemisphere, you can capture Scorpio, Centaurus, Crux, and Sagittarius.

However, for larger objects such as Draco, it would be best to use a shorter focal length such as 18mm to capture more details because Draco spans about 10 degrees of the night sky, which is about 20 times the size of the Orion constellation.

Screenshot of Orion in Stellarium

The example lens in this range is the very common nifty fifty. It is a relatively inexpensive and widely available lens, it can be used to capture both constellations and the Milky Way core alongside the Lagoon Nebula. There are fast aperture 50mm primes, such as the 50mm f/1.4 and the 50mm f/1.2. Their larger aperture allows for more light to enter the lens when shooting in darker conditions.

To keep the stars sharp, it’s better to use a star tracker. A star tracker is a device that helps to reduce star trails when taking astrophotography images. It uses motors to keep the camera pointed at a certain point in the sky, which allows for longer exposures and sharper stars. Additionally, its adjustable speed allows the photographer to customize the rate of tracking so that the shutter speed can be adjusted to achieve the desired result.


Depending on the camera equipment, you can capture a wide variety of large deep sky objects with lenses of 70-300mm focal length. Examples include the Lagoon Nebula, Omega Centauri, and galaxies such as Andromeda and Triangulum.

Screenshot of Andromeda in Stellarium

The Rokinon 135mm lens is a great budget-friendly choice in this range. It works best on crop sensor cameras and provides a wide field of view, making it ideal for capturing large objects like the Veil Nebula complex.

Its fast f/2 aperture produces sharp images, while its narrow field of view enables you to capture stunning panoramas of the night sky by combining different images. Additionally, this manual lens allows you to set the focus and lock it in, so your zoom won’t slip.

The Sony 100-400mm f/4.5-6.3 lens is an excellent choice for deep astrophotography, as it provides a wide range of focal lengths (100-400mm) that can be used to capture distant objects like the Andromeda Galaxy and other nebulae. It can be paired with the Sony FE 1.4 X Teleconverter for even greater reach, making it a versatile tool for astrophotography.


For this longer focal length, consider investing in a Sigma 150-600mm zoom lens, as it produces sharp, vibrant images even when stopped down. Sony FE 200-600mm f/5.6-6.3 is also great for certain astronomical objects and other elements like the moon.

But it is also common to start with telescopes. Telescopes typically come equipped with a mount, tripod, and eyepiece or camera adapter to allow for easy tracking of celestial objects. They are specifically designed to capture detailed images of faint deep sky objects and have much larger apertures than camera lenses for collecting more light.

Telescopes also allow for larger fields of view and have adjustable settings for focus and magnification that help bring out the details in faint deep sky objects. They acts as a super-telephoto lens, with typical focal lengths ranging from 400mm to well over 2000mm. Buying a camera lens at the same exact focal length is way pricier.

The Celestron NexStar 8SE is one of the best entry-level telescopes for astrophotography. It is compatible with both DSLR cameras and astronomy cameras. It’s designed to be accessible, allowing you to quickly and easily find and track objects in the night sky. Its 8″ aperture is large enough to capture stunning images of the moon, planets, nebulae and galaxies.

FAQ about Best Focal Lengths for Astrophotography

What is the best focal length for deep sky photography?

A slightly longer focal length is the better option for deep sky photography. You can get a 100-300mm lens without a telescope. Cheaper lenses will work as long as you have a decent aperture.

What is the best focal length for the Milky Way?

A wide angle lens is best for photographing the Milky Way and the night sky. I recommend a lens such as 16mm, 14mm, or even 20mm to photograph the Milky Way.

Is a 50mm lens good for night sky photography?

A 50mm lens can be a great option for night sky photography because it offers a wide field of view and a moderate level of magnification. In addition, you can use a prime lens with a fast aperture of f/1.8 or brighter, allowing more light to hit the sensor, which is essential for night sky photography. Shutter speeds should be limited to 10 seconds or less at 50mm in full frame to limit star trails, while star stacking can be used to average multiple exposures to get sharper stars and reduce noise.

Is 24mm wide enough for Milky Way?

Yes, 24mm is wide enough for Milky Way photography. But if you want to capture the Milky Way in its entirety, you will need to use a 16mm or wider lens on a full frame camera. A 24mm lens will give you a good overview of the Milky Way, but will not capture all the details of the galaxy.

Is 14mm too wide for astrophotography?

No, 14mm is not too wide for astrophotography. In fact, it is a great starting point for beginners, as it can provide a wide field of view that is ideal for capturing expansive deep space objects such as star clusters and galaxies. Be aware, however, that a 14mm lens produces a significant amount of distortion, so you may want to invest in a higher quality lens with a wider field of view if you are serious about astrophotography.

Closing Words

Astrophotography can be a great way to explore the night sky. With the right equipment and a bit of planning, you can take stunning photos of deep space objects like galaxies, nebulae, and star clusters. By understanding focal lengths, previsualizing and planning with Stellarium, and investing in the right camera lenses and telescopes, you can capture the perfect shot. So get out there and start exploring the night sky today!

Meet the Author

Wei Mao

Wei was a cruise photographer who worked at Disney Cruise Line. He is a lucky traveler who has been to more than 20 countries with his camera while working on an around-the-world cruise. Photography has changed his view of the world forever. Now he wants more people to benefit from photography through his blog.

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