Light Pollution & Sky Quality
Aurora is a faint-light phenomenon. The brightest displays are visible even from suburban backyards, but most aurora — especially from Australian and New Zealand latitudes — is subtle. Dark skies make the difference between seeing a faint green glow on the horizon and seeing nothing at all.
What is SQM?
SQM stands for Sky Quality Meter, and it's measured in magnitudes per square arcsecond (mag/arcsec²). It's a logarithmic scale — every increase of 1 means the sky is about 2.5× darker. Higher numbers = darker skies.
Lumina stores an SQM value for each of your saved locations, fetched automatically from the lightpollutionmap.info API. In Field Mode, Lumina also displays the live SQM for your current GPS location so you know exactly what you're working with. Here's what the numbers mean in practice:
| SQM | Sky class | What you can see |
|---|---|---|
| < 18.0 | Inner city sky | Only the brightest aurora. Skyglow dominates. Not recommended. |
| 18.0–19.0 | Bright suburban | Major storms visible. Subtle displays lost in the glow. |
| 19.0–20.0 | Suburban sky | G2+ storms visible. Decent for strong events. |
| 20.0–21.0 | Rural/suburban transition | Good for most aurora. Milky Way visible. Worth the trip. |
| 21.0–21.5 | Rural sky | Excellent. Faint aurora visible. This is your target. |
| 21.5–22.0 | Excellent dark sky | Pristine. Even weak aurora stands out clearly. |
| > 22.0 | Pristine dark sky | As good as it gets. Every photon counts. |
Why dark skies matter for aurora
Aurora light is concentrated in a few specific wavelengths. The green 557.7 nm oxygen line is the brightest, but from Australian and New Zealand latitudes most visible aurora is actually the red 630 nm oxygen emission — because the green emission sits lower in the atmosphere (110–250 km) and is often below the horizon for equatorward observers, while the red emission occurs higher up (200–400 km) and clears the horizon. That's good news for contrast, because monochromatic light stands out better against a dark sky than broadband light sources would. But it's still competing with all the scattered artificial light in the atmosphere above cities and towns.
Light pollution affects aurora viewing in two ways:
- Skyglow — artificial light scattered by the atmosphere creates a background glow that reduces contrast, especially near the horizon where most aurora appears.
- Direct glare — nearby streetlights, house lights, or car headlights ruin your dark adaptation. It takes 20–30 minutes for your eyes to fully dark-adapt, and one flash of white light resets the clock.
The southern horizon is everything
For Australian and NZ aurora watchers, the display is usually low on the southern horizon. This means:
- Your southern sky needs to be dark . A city to your north is less of a problem than a town to your south.
- Horizon obstructions matter — hills, trees, and buildings to your south can completely block a display that's only a few degrees above the horizon.
- A location with SQM 20.5 but a clear, flat southern horizon over the ocean will beat a location with SQM 21.5 that has hills to the south.
How to set up good viewing locations
When you save a location in Lumina, its SQM is fetched automatically from the lightpollutionmap.info API, and its horizon profile is computed from PVGIS terrain data — no manual fiddling required. Here's how to find good spots:
- Use a light pollution map (like lightpollutionmap.info ) to find dark areas within driving distance.
- Look for locations with a southern ocean horizon — beaches, headlands, and south-facing lookouts are ideal. No land means no artificial light to the south.
- Lumina uses PVGIS terrain data to calculate the maximum obstruction angle across your southern horizon (150°–210°). This shows up in your location details — you'll see the elevation and horizon angle automatically.
- If you have an actual SQM meter (or a phone app that approximates one), take a reading on a moonless night for the most accurate value.
Lumina uses your location's SQM and horizon obstruction data in the viewing recommendation — a pristine-dark-sky location with a clear southern horizon will get a better verdict for the same aurora probability than a suburban one with hills to the south. That's realistic: the same display looks dramatically different under different sky and terrain conditions.