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August 20, 2024
Long exposure astrophotography is the technique of keeping your camera shutter open for several seconds — or even minutes — to collect enough light from distant stars, nebulae, and galaxies. Unlike daytime photography, the night sky demands extended exposures to reveal detail invisible to the naked eye. The longer the shutter stays open, the more photons hit your camera sensor, transforming a dark, featureless sky into a breathtaking field of stars. Mastering long exposure astrophotography is the foundation of every great night sky image, and understanding the core principles will immediately improve your results whether you are shooting from a city backyard or a remote Australian dark sky site.
The night sky is an exciting canvas filled with celestial wonders waiting to be marvelled at and photographed. Astrophotography — the art of photographing these wonders — allows us to gaze deeper into the cosmos and reveal details invisible to the naked eye. But astrophotography is a unique discipline, requiring specialised techniques to overcome the challenges of low-light conditions.
Long exposure is one of the most powerful tools in an astrophotographer's arsenal. By keeping the camera shutter open for extended periods, we can gather more light, revealing the faint stars, nebulae, and galaxies that would otherwise be lost in darkness. However, long exposures also introduce challenges like star trails and noise.
Novatech Direct is passionate about helping you capture the magic of the night sky. In this blog post, we'll delve into essential long-exposure astrophotography tips to help you along.
To capture the beauty of the night sky, you'll need the right tools to overcome the challenges of long exposures. Here are some essential pieces of equipment.
Once you have the right gear, it's time to dial in the perfect settings for your long exposures. Here's a breakdown of the key settings to consider.
Beyond the essential gear and settings, these additional tips can help you take your astrophotography to the next level.
Here's a selection of the best cameras and lenses to help you capture stunning astrophotography images.
Long exposure astrophotography is the foundation of virtually every stunning night sky image you've ever seen. When your camera's shutter stays open for several seconds — or even several minutes — it collects far more photons of light than your eye ever could, transforming a dark, sparsely dotted sky into a breathtaking tapestry of stars, Milky Way arcs, and glowing nebulae. Understanding the core principles behind long exposure astrophotography is what separates a frustrating night in the field from a memory card full of keepers.
In long exposure astrophotography, exposure duration is a balancing act. Expose for too short a time and you won't gather enough light to reveal faint celestial objects. Expose for too long on a static tripod and Earth's rotation will cause stars to trail across the frame as elongated streaks rather than crisp points of light. The sweet spot depends on your focal length, sensor size, and whether you actually want star trails or sharp stars.
As a starting point for sharp stars without a tracking mount, most astrophotographers work with exposures between 15 and 30 seconds at wide focal lengths. From there, you layer multiple exposures in post-processing — a technique called image stacking — to build up the total light gathered without introducing trailing. This is one of the most powerful strategies in long exposure astrophotography because it reduces noise, recovers fine detail, and produces results that a single ultra-long exposure simply cannot match.
Unlike daytime photography where light is abundant, long exposure astrophotography punishes guesswork. Even a small amount of ambient light pollution, an unexpected passing car, or a slight vibration from the wind can ruin an otherwise perfect frame. Before you shoot, use a light pollution map to find a dark site, check the lunar calendar to avoid shooting near a full moon A lunar eclipse is also worth planning around — check out our tips for photographing a lunar eclipse to make the most of this dramatic night sky event., and always arrive early enough to let your eyes — and your camera sensor — acclimatise to the darkness. Planning apps like Stellarium or PhotoPills allow you to visualise exactly where the Milky Way core will be at any given hour, helping you compose your shot before you even leave the house. Preparation is the difference between a productive night and a wasted one in long exposure astrophotography.
Stacking is a post-processing technique where multiple exposures of the same scene are aligned and averaged or combined to reduce random sensor noise while preserving genuine signal from stars and nebulae. Free tools like Sequator (Windows) and Starry Landscape Stacker (Mac) make this accessible even for beginners. For a typical Milky Way shot, capturing between 10 and 20 individual frames and stacking them can dramatically improve the signal-to-noise ratio compared to a single long exposure — giving your images a cleaner, more professional finish straight out of your processing software.
One of the first creative decisions you'll make in star long exposure photography is whether you want your stars to appear as pinpoint dots of crisp light, or as sweeping circular trails that trace the rotation of the Earth across the sky. Both are legitimate and visually spectacular outcomes — but they require very different technical approaches, and understanding each will unlock a whole new dimension of what's possible after dark.
If your goal in star long exposure photography is pinpoint stars, your maximum exposure time is governed by your focal length and sensor crop factor. The widely-used 500 Rule gives you a quick starting calculation: divide 500 by your effective focal length to get the maximum exposure time in seconds before stars begin to trail noticeably. For example, using a 24mm lens on a full-frame camera gives you approximately 500 ÷ 24 = 20 seconds. On a crop sensor camera (APS-C with a 1.5x crop factor), the same 24mm lens has an effective focal length of 36mm, giving you roughly 500 ÷ 36 = 13 seconds.
Many modern astrophotographers prefer the more conservative NPF Rule, which factors in aperture and pixel density for greater precision — particularly useful with high-megapixel sensors where pixel-level star trailing becomes visible even within the 500 Rule's limits. Apps like PhotoPills calculate the NPF Rule automatically once you enter your camera and lens details, making it easy to dial in on location.
Star trail photography is the other side of the coin. Here, you deliberately embrace the Earth's rotation to create long, arcing light streaks across the sky. To create star trails, you have two main approaches: a single very long exposure (often 30 minutes to several hours using Bulb mode) or a sequence of shorter exposures later blended together using dedicated software like StarStaX. The latter approach is generally preferred because it avoids the significant noise build-up and battery drain that accompany extremely long single exposures, and it also protects you against losing an entire session to a single interruption like a passing car or plane.
For the most dramatic star trails, aim your camera toward the south celestial pole (in the Southern Hemisphere, look near the Southern Cross and the pointer stars to locate it). Stars close to the celestial pole produce tight, circular arcs, while stars near the horizon produce longer, shallower curves. Including a compelling foreground — a lone tree, a lighthouse, an outback rock formation — anchors your star trail long exposure and gives the image a strong sense of place that elevates it beyond a simple technical exercise.
Regardless of whether you're shooting for sharp stars or trails, certain settings form the baseline for star long exposure photography. Start with your aperture wide open (f/1.8 to f/2.8 is ideal) to maximise light gathering. Set your ISO between 1600 and 6400 depending on your camera's noise performance — modern mirrorless cameras from Sony, Nikon, and Canon handle high ISO remarkably well. Always shoot in RAW format to preserve maximum dynamic range for post-processing. Use manual focus and zoom into a bright star on your live view screen at 10x magnification to achieve precise focus, since autofocus systems struggle in low light. Finally, use a remote shutter release or your camera's built-in timer delay to eliminate any vibration from pressing the shutter button — even a small shake during a 20-second exposure will soften your stars.
Getting your star long exposure settings right is the single biggest factor separating sharp pinpoint stars from blurry streaks. As Earth rotates, stars appear to move across the frame — too long an exposure and you will capture star trails rather than crisp points of light. A reliable starting point is the 500 Rule: divide 500 by your lens focal length to get the maximum shutter speed in seconds before trailing becomes visible. For example, a 24mm lens gives you roughly 20 seconds. On a crop-sensor camera, use the 300 Rule instead. Pair this with a wide aperture (f/1.8–f/2.8) and ISO 1600–6400 to expose correctly without excessive noise. A sturdy tripod and remote shutter release are non-negotiable for any star long exposure.
If you enjoy pushing your camera to its limits in extreme weather conditions, our guide on how to capture lightning photos covers another thrilling area of weather and nature photography worth exploring.
If you enjoy night-sky events and outdoor celebrations, our guide on how to photograph fireworks covers the settings and techniques you need to capture dazzling displays with the same long-exposure precision.
