NHT · Night & Astro
Photographing the Milky Way: Settings That Work
Plan the season, find a dark sky, and use the 500 rule with ISO 1600-3200 to capture the galactic core without star trails.
Diagrams
The Milky Way's bright core is not visible all year. In the northern hemisphere it rises from roughly February to October, and the best months for a high, bright arc are May through August. You need a genuinely dark site — Bortle class 4 or darker — and you should shoot at least an hour after astronomical twilight ends, with no moon in the sky. Plan with an app such as PhotoPills or Stellarium so you know exactly where and when the core will appear; guessing wastes the whole night.
Exposure is a balance between light and star motion. Use the widest aperture your lens has, typically f/2.8 or faster, and set ISO between 1600 and 3200. For shutter speed, apply the 500 rule: divide 500 by your full-frame focal length. A 20mm lens gives 25 seconds. On high-resolution bodies, be more conservative and use the 400 or 300 rule instead, because the extra pixels reveal trailing in the corners long before it shows in the centre. Crop-sensor cameras should use the equivalent focal length in the calculation.
Focus is where most people fail. Autofocus cannot lock onto stars, so switch to manual, open live view, zoom to 10x on the brightest star you can find, and turn the ring until the star is the smallest possible point. Check a test frame at 100% before you start your real sequence. If your lens has a hard infinity stop, do not trust it — nearly all lenses focus a little past true infinity.
Composition and processing finish the job. Include a foreground — a rock formation, a road, a tent — and expose a second frame for it, then blend, because the sky and the land rarely share the same exposure. Shoot in RAW and expose to the right: the histogram should have data in the middle, not crushed against the left edge. In editing, set white balance to around 3800 to 4000K for a natural look, lift the shadows gently, and apply modest noise reduction. The classic mistakes are a shutter too long for the focal length, which smears the stars into dashes, and shooting from a site that looked dark to your eyes but is far too bright for a 20-second exposure.
Key points
- Shoot the core from May to August in the northern hemisphere, at a Bortle 4 or darker site, an hour after astronomical twilight.
- Use f/2.8, ISO 1600-3200, and the 500 rule (500 divided by focal length) for shutter speed; use the 400 rule on high-resolution sensors.
- Focus manually in live view at 10x on a bright star — never trust the hard infinity stop on the lens.
- Expose to the right in RAW, blend a separate foreground frame, and set white balance near 3800-4000K in post.
