---
title: "Image Stacking — Why More Frames = Less Noise"
canonical: https://stackingstarlight.com/stacking
description: "Stacking aligns and combines many calibrated frames to raise SNR by √N, with dithering and sigma clipping to reject artifacts."
---

# Image Stacking — Why More Frames = Less Noise

> Stacking aligns and combines many calibrated frames to raise SNR by √N, with dithering and sigma clipping to reject artifacts.

Stacking is how random noise is beaten. Averaging N frames improves signal-to-noise by **√N** (4 frames → 2×, 100 frames → 10×). Frames are first **registered** (aligned on stars), then combined. **Sigma clipping** rejects pixels that deviate too far from the median — removing satellite trails, cosmic rays, and plane lights without harming real signal. **Dithering** (shifting the mount a few pixels between frames) decorrelates fixed patterns and walking noise so they average away during integration. Total integration time is the real lever: more, longer, well-dithered subs make cleaner images.

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Source: [https://stackingstarlight.com/stacking](https://stackingstarlight.com/stacking) · Part of [Stacking Starlight](https://stackingstarlight.com) by Michael Kalika.

LLM resources: [LLM index (llms.txt)](https://stackingstarlight.com/llms.txt) · [Complete LLM text (llms-full.txt)](https://stackingstarlight.com/llms-full.txt) · [Markdown homepage (index.md)](https://stackingstarlight.com/index.md)