Astroguide

Shoot and stack a night sky photo, step by step

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A field guide in two parts

Shoot the sky, then bring it out

Part one is what happens under the stars with the camera. Part two is the five minutes at a laptop afterwards that turns a faint frame into a real photo.

Part one — in the field

Turn the mode dial to M. Then MENU → Shooting Menu → Image quality → NEF (RAW). RAW keeps the hidden detail that stacking later needs.
Press the i button (bottom-right of the back screen), navigate to Focus mode in that quick-access panel, and select MF. Autofocus can’t find stars in the dark — it hunts and gives up. From here focusing is done by hand.
Mode dial on M. Shutter 15″, aperture as wide as your lens allows (f/3.5 on the kit lens at 18mm), ISO 3200. Zoom the lens to its widest.
Pressing the shutter with your finger shakes the camera enough to blur stars. A short delay lets that vibration die away first — free, and it matters.
Enter live view, zoom in on the brightest star you can see, and turn the focus ring slowly until it’s the smallest, tightest point. Then don’t touch the ring again.
Fire the shutter, then zoom into playback. Stars should be pinpoints, not discs. Frame should look roughly half-bright — raise ISO if it’s too dark.
Once a frame looks right, don’t move anything. Shoot 20 more of the same view, then cap the lens and shoot 10 more identical — these become your noise reference.

Part two — at the laptop

Free, Windows only, no account needed — sequator.free.fr. A small, plain program, nothing like Photoshop’s learning curve.
‘Star images’ → your 20–30 sky frames. ‘Noise images’ → your 10 lens-cap-on frames. That’s the only input it needs.
Turn on Composition → Sky region and let it auto-detect the sky. Leave everything else on default for your first attempt.
Sequator aligns and stacks every frame, subtracting sensor noise using the dark frames. A minute or two, then out comes one clean TIFF.
Often that’s enough on its own. To go further, open the TIFF in free software like RawTherapee and nudge contrast and shadows up until it looks right to your eye — there’s no formula, just a slider and a feeling.