Is a full moon bad for aurora viewing?

Only for faint displays. A strong, active aurora (the kind worth travelling for) is bright enough to show well despite a full moon. But for marginal nights, a bright moon can be the difference between MAYBE and NO — which is why it carries 15% of our score.

What moon phase is best for the northern lights?

New moon, or evenings when the moon has already set: the darkest possible sky maximises contrast for faint structures. Within any moon phase, the hours when the moon is below the horizon are the best viewing hours.

Moon Phase vs Aurora Visibility: When Moonlight Actually Matters

The moon is the most over-rated aurora villain and the most under-used planning tool. The truth is nuanced: moonlight never hides a strong display, but it quietly erases the faint ones — and moon timing changes what you see more than moon phase alone suggests.

What moonlight actually does

Moonlight is scattered sunlight; it raises the sky's background brightness exactly like light pollution does. Against that brighter floor: faint arcs lose contrast first, then diffuse glows, and finally — only during a bright moon plus weak activity — even active arcs look subdued. The aurora's colour and motion remain visible whenever the display itself is strong. "Full moon kills aurora" really means "full moon kills faint aurora".

The timing detail: moon altitude

Illumination percentage ignores where the moon is. A gibbous moon below the horizon contributes nothing; a "100%" full moon that rises at midnight only matters for the second half of the night. Around high latitudes the winter full moon rides high all night, while a new moon gives every hour of the night dark skies. That's why planning around the lunar calendar beats reacting to it.

How to plan around it

Priority order for a fixed trip: (1) pick the dark-sky window closest to new moon, (2) within that week, target the equinox storm statistics, (3) on any given night, put moonless hours first. Our engine folds current moon illumination into every score at 15% weight — and the 27-day outlook lets you cross-check moon phases against the Kp trend before booking anything.

Using the moon in practice

Check the moon factor on your city page — it shows tonight's illumination percentage folded into the score. The planning rule: book trips for the week around new moon when you can, and when you can't, schedule viewing hours for when the moon is below the horizon or low — moonrise and moonset times are in any almanac and worth the lookup. During a bright-moon week, shift your expectations from "photograph faint rays" to "watch a strong display", and prioritise the hours around moonset or before moonrise. The 27-day outlook exists precisely so you can cross-check hot Kp windows against the lunar calendar before booking anything.

Common moon mistakes

Cancelling a trip for a full moon: strong displays shine through moonlight; you'd be skipping good nights. Ignoring moonrise timing: illumination percentage says nothing about when the moon is actually up — a "100%" moon below the horizon during your window is a non-factor. Blaming the moon for a quiet sun: a moonless NO night is still a NO; the moon is a modifier, never the headline.