Tutorial
How to stack Milky Way photos step by step
Image stacking combines multiple exposures of the same scene to reduce sensor noise without sacrificing resolution. This guide walks through the complete workflow: from exporting your RAW files to finishing the stacked result in Lightroom.
What you need before you start
Multiple frames of the same scene
8 to 20 exposures shot in sequence from a fixed tripod position. All frames should use the same focal length, aperture, and ISO.
Consistent exposure settings
Stacking frames shot at different ISOs or shutter speeds produces poor results. NightScape Stacker will flag any mismatches before you begin.
RAW files (or pre-exported TIFFs)
If you have RAW files, export them as 16-bit TIFF from Lightroom or Capture One first. Do not apply any tone adjustments before stacking.
NightScape Stacker
Available for Mac, Windows, and Linux. $99 one-time purchase.
The steps
Export your frames as 16-bit TIFF files
NightScape Stacker works with 16-bit TIFF files (.tif, .tiff). Export your RAW files as 16-bit TIFF from Lightroom or Capture One before loading them. This preserves the full dynamic range you captured in camera. Export all frames at the same settings: same white balance, same lens profile correction, no exposure adjustments.
Tip: Do not batch-process exposures in Lightroom before stacking. Let NightScape Stacker do the averaging first, then finish the image.
Load your frames into NightScape Stacker
Drag and drop your exported TIFF files into NightScape Stacker. It reads the EXIF data from each frame and checks for consistency. If frames were shot with different ISO settings, shutter speeds, or lenses, it will flag the mismatches before you start. This matters: stacking incompatible frames degrades the result instead of improving it.
Tip: Aim for 8 to 25 frames from the same shooting session. Stacking 4 frames roughly halves the shot noise. Stacking 16 frames cuts it to about a quarter. Beyond 25 frames the improvement per additional frame becomes small.
Stack
NightScape Stacker aligns each frame to compensate for Earth's rotation between exposures, then combines them using sigma-clipped mean averaging. The alignment handles the sky independently from the foreground, so your mountain or tree line stays sharp while the stars align correctly. The stacked result has dramatically less noise than any single frame.
Tip: For Milky Way photography, the sky and foreground move differently between frames. NightScape Stacker aligns the sky across frames. You will composite the stacked sky with a single-frame foreground in Lightroom or Photoshop afterward.
Remove the light pollution gradient (optional)
After stacking, open the gradient removal tool. Light pollution from cities and towns creates uneven brightness and color gradients across the sky that become more visible after stacking. NightScape Stacker uses a sigma-clipped sampling grid and polynomial correction to lift the gradient while preserving the natural tones of your scene. Adjust the correction strength with a live preview until the sky looks natural.
Tip: Gradient removal is optional. If you shot from a truly dark site with no visible gradient, you can skip this step.
Remove or reduce the stars (optional)
The star removal or reduction tool shrinks or removes stars that are drawing attention away from the Milky Way core. Use the live overlay to see exactly what will change before committing. Adjust the size threshold to target the largest bloated stars without affecting smaller pinpoints. Two modes are available: shrink (reduces star size) and remove (eliminates stars entirely).
Tip: Star removal or reduction is optional and works best applied selectively. Many photographers skip it entirely or apply it lightly, then make further adjustments in Lightroom or Photoshop.
Export and finish in Lightroom
Export the processed image as a 16-bit TIFF. This preserves the full dynamic range for editing in Lightroom or Photoshop. Open the exported TIFF in Lightroom and apply your tone, color, and exposure adjustments. The stacked and cleaned image responds much better to editing than any single frame, with more shadow detail to pull from and cleaner highlights to work with.
Tip: NightScape Stacker handles the technical processing. The creative work happens in Lightroom. Keep the two stages separate.
How many frames should you stack?
The noise reduction from stacking follows the square root of the number of frames. Stacking 4 frames roughly halves the shot noise. Stacking 16 frames cuts it to about a quarter. Each additional frame helps, but with diminishing returns. The visible improvement slows significantly past around 25 frames.
The practical sweet spot for most nightscape photographers is 8 to 25 frames. This means a shooting session of 5 to 12 minutes at the same composition before moving on. Shoot more if the sky is cooperating. There is no upper limit.
One practical note: these numbers apply to shot noise, which is the dominant noise source in typical nightscape exposures of 15 to 30 seconds. Keep your individual exposures long enough that the sky is actually bright. Very short sub-exposures shift the noise balance toward read noise, which does not improve with stacking the same way.
4 frames
~50% less noise
9 frames
~67% less noise
16 frames
~75% less noise
25 frames
~80% less noise
Ready to stack your frames?
NightScape Stacker handles the complete workflow. $99 one-time, Mac, Windows, and Linux.
Coming SoonAlso: Why stacking matters · FAQ