Module 04 · 7 min · Intermediate

Noise vs Signal

How to distinguish useful signals

Real spectrum: Orion Nebula, one cube pixel

DR1 cube

Extracting spectrum from the science cube… 0.0s

Toggle the robust/full-range scale (top-left of the chart) and look for single-channel spikes versus smooth multi-channel structure.

Signal-to-noise

S/N compares a measurement with its uncertainty. S/N > 5 is rarely produced by random noise — but systematics can still exceed it.

A lone high value in one channel is usually a cosmic ray or detector artefact. Real astrophysical features are spectrally smooth across neighbours.

Charts default to a robust percentile scale so one spike doesn't flatten everything else; clipped points are marked with a triangle.