The 500 rule (sharp, pinpoint stars)
Longest shutter before stars trail = 500 ÷ focal length (35mm-equivalent), in seconds.
| Lens (FF) | Max shutter |
|---|
| 24mm | ~20–21 s |
| 50mm | ~10 s |
The wider the lens, the longer you can expose.
Settings to start from
- Aperture: as wide as possible — f/1.4 on the 24mm GM (a fast f/1.2–f/1.4 lens is ideal; f/2.8 is the slow limit).
- Shutter: from the 500 rule (e.g. ~20 s at 24mm).
- ISO: 1600–3200 (works in the 1000–6400 range); a common start is f/1.4, ~10 s, ISO 3200, then adjust.
- Focus: manual to infinity (or on a bright star with magnified live view).
Technique
- Get away from city lights — light pollution washes out stars.
- Sturdy tripod + remote or timer; on a DSLR lock the mirror up, on mirrorless use a short delay.
- Turn on Long-Exposure Noise Reduction (dark-frame subtraction) — it doubles the wait but cleans hot pixels.
- Shoot RAW; sort white balance later.
- Let night look like night — err darker, ideally in post. Watch the moon; it changes everything.
Composition
Include foreground (trees, hills, buildings) for depth, place the horizon low to emphasise sky, and look for the Milky Way or recognisable constellations. Reduce noise and lift contrast between stars and sky in post.
The 500 rule on a crop sensor
Do the crop-factor maths first: focal length × crop factor, then divide into 500. A 50mm on APS-C (Sony 1.5×) is a 75mm equivalent → 500 ÷ 75 ≈ 6 s. Always round down. The 600 rule buys light at the cost of visible trailing — prefer 500. Sharp stars with one or two streaks isn't a failure of the rule; that's an aircraft contrail or a meteor.
Set-up details that matter
- Remove the UV filter — it throws reflections around bright stars.
- SteadyShot off on the tripod, and Optical SteadyShot off on the lens.
- Long Exposure NR on (or Auto) for single frames: the camera shoots a matching dark frame and subtracts the hot pixels. Turn it off when stacking, or you halve your capture rate.
- Manual Focus (MF) at infinity, confirmed with Focus Magnifier on a bright star — then don't touch it.
- Remote release, or the 2-second Self-timer on a solid tripod.
- Shoot RAW and settle White Balance later.
- Deliberately underexpose a little if you want the frame to read as night; it's easier to lift than to make a bright frame look dark.
Typical opening frame from the references: 10 s at f/1.4, ISO 3200, then bracket the length longer and shorter with ISO compensating. Keep notes. For planning where the Galactic Core will actually be, see Milky Way Planning.
Consolidated from notes: Star & Moon photography; How to use the Sony FE 24mm F1.4 GM for night sky (astro); including stars in your landscapes (Len's School)