The Viewing Recommendation Engine
The aurora probability tells you whether aurora is likely happening . The viewing recommendation tells you whether it's worth going outside to look . These are two different questions, and answering the second one means accounting for a bunch of earthly factors that have nothing to do with space weather.
What goes into the recommendation
Lumina's recommendation engine weighs up five factors:
- Space weather — the aurora probability (both Field and Plan modes), substorm state, CME alerts, and HP forecast.
- Sky darkness — is it astronomically dark right now? How many hours of darkness are left? When does twilight start?
- Moon — how bright is the moon, is it up during the dark window, and how much is it washing out the sky?
- Cloud cover — what's the cloud percentage in each direction, is a clearing expected, and is it worth driving somewhere else?
- Light pollution — what's the sky quality (SQM) at your viewing location, and how much does artificial light reduce contrast?
The decision tiers
All five factors get combined into a single verdict with one of four severity levels:
| Verdict | What it means | Typical scenario |
|---|---|---|
| Excellent | Very favourable — go if you can | High probability, dark sky, no moon, clear southern horizon |
| Good | Worth heading out | Moderate probability, decent darkness, some moon or cloud but manageable |
| Fair | Marginal — could go either way | Low-ish probability or significant moon/cloud, but not hopeless |
| Poor | Probably not worth the effort | Very low probability, daylight, full moon, or solid cloud cover |
Sky darkness — it all starts here
You can't see aurora during the day, and you can't see it well during twilight. Lumina calculates astronomical twilight times for your location (when the Sun is 18° below the horizon — truly dark) and builds a darkness window.
But even within astronomical night, the sky isn't perfectly dark if the moon is up. Lumina's sky brightness model combines sun altitude and moon illumination into a continuous darkness score that gets sampled every 5 minutes through the night. The result is a complete darkness window — the actual periods when the sky is dark enough for aurora viewing, accounting for both sun and moon.
Cloud cover logic
Cloud cover is assessed in five directions (centre, north, south, east, west) using data from Open-Meteo. Lumina picks the direction with the lowest cloud cover as your "best bet." If the centre and south are both heavily clouded but there's a clearing expected within the next few hours, the recommendation will tell you when to check again.
The worth travelling flag takes it a step further: if your current location is clouded out but another saved location has clear skies and the aurora probability justifies the drive, Lumina will suggest heading there instead.
How Lumina picks your best location
If you've saved multiple viewing locations, Lumina automatically ranks them for each night based on:
- Aurora elevation — higher elevation above the southern horizon is better (less atmospheric extinction, less likely blocked by terrain).
- SQM (sky darkness) — darker skies mean better contrast for aurora.
- Cloud cover from sunset — the forecast cloud percentage for the evening window.
The best location gets highlighted in the recommendation.
Putting it all together
The recommendation engine doesn't use a simple weighted formula — it's a decision tree that considers the practical reality of aurora watching. Some examples of its logic:
- High probability but full moon overhead? The verdict might be "Fair" with a note that brighter displays will still be visible despite the moon.
- Low probability but pristine dark sky and a CME arriving soon? "Fair to Good" — worth staying out in case conditions improve.
- Good probability but 100% cloud cover with no clearing expected? "Poor" — the aurora might be happening but you won't see it.
The recommendation is ultimately a guide, not a guarantee. Aurora watching involves persistence & a little luck, and conditions can change quickly. When in doubt, check the magnetometer signals and the substorm state — if multiple ground stations are active, there's a good chance something is visible.