Common questions

Check the "Tonight's Chance" panel at the top of the Live page. It combines the Hp30 forecast, your local cloud cover, moon phase, and darkness to give you a plain-English answer. For the best chance you need: Hp30 4 or higher, dark skies (no moon, away from light pollution), and clear skies.

Hp30 4 brings the aurora to Scotland. Hp30 5 reaches northern England. Hp30 6 extends to central England. Hp30 7+ can cover most of the UK including London and Wales. The threshold shifts south as Hp30 rises, rather like a tide coming in.

Hp30 is a geomagnetic index from GFZ Potsdam that measures how disturbed Earth's magnetic field is on a scale of 0 to 9. It is the same scale as the older Kp index, but recalculated every 30 minutes instead of every 3 hours. That extra resolution catches the sharp onset of a substorm far sooner than Kp does.

Bz is the north-south component of the solar wind's magnetic field. When it turns negative (southward), it connects with Earth's magnetosphere and energy flows in to power the aurora. Bz going below −10 nT is a very good sign, so go outside immediately. It's the single most important real-time number.

The equinoxes, late March and late September, tend to produce more frequent geomagnetic storms due to the alignment of Earth's magnetic field with the solar wind. Winter (October to February) also works well because nights are long, giving more dark sky time. Summer is mostly useless in Scotland and further north because nights barely get dark. In June and July north of 57°N there is no astronomical darkness at all.

Astronomical twilight ends when the Sun is more than 18° below the horizon. At that point the sky is truly dark and even faint astronomical objects become visible. In the UK this typically starts around 11 pm in spring and autumn and 1 to 2 am in early summer. Sky Tonight shows you the exact dusk-to-dawn dark window each night, or warns you if there is no astronomical darkness (common in Scotland during June and July).

Noctilucent clouds are wispy, electric-blue clouds that form at around 80 km altitude, far higher than ordinary clouds, and are lit by the Sun even after it has set. They appear in the northern sky during late June and July, roughly between latitudes 50 and 65°N. Sky Tonight shows an NLC alert panel during the season (June and July) so you know when to look north around midnight.

Only if Hp30 is low. At Hp30 5+ you have a good chance from northern England. At Hp30 7+ it can be visible from London and the south. For any display, you need dark skies. Rural areas away from city glow give the best results, wherever you are.

Yes, at Hp30 5+, the aurora should be faintly visible to the naked eye from Scotland or a dark site in northern England, usually as a green or whitish glow on the horizon. Stronger storms (Hp30 7+) show vivid green and often pink or red rays that are unmistakably aurora. Cameras pick it up more easily than your eyes at first.

Yes, and modern smartphones are excellent. iPhone: use Night mode or a Pro/manual camera app. Pixel: Astrophotography mode in Google Camera. Other Android: Pro mode with ISO 1600 and a 5 to 10 second exposure. Key rule: keep the phone completely still (lean it against something or use a small tripod).

A good starting point for a DSLR or mirrorless: ISO 1600, shutter 10 to 15 s, aperture f/2.8 or wider. During an active display, drop the shutter to 3 to 6 s to freeze the motion. Use our Settings Calculator on the Guide page. It adjusts recommendations for your sensor type and activity level.

No. A smartphone on Night mode can take stunning aurora photos. An entry-level DSLR or mirrorless with a kit lens will give you a clear step up. You only need the more expensive gear (fast wide primes, full-frame sensors) if you want to push into video, timelapse, or very faint displays.

Use the 500 rule: divide 500 by your focal length × crop factor to get the maximum shutter time before stars streak. For a 24mm lens on APS-C (crop 1.5): 500 / (24 × 1.5) ≈ 14 seconds. Our Settings Calculator does this for you automatically.

Almost always camera shake. At 10+ second exposures even breathing can blur a shot. Use a tripod, set a 2-second self-timer or a remote shutter release, and turn off image stabilisation (it can fight against a stationary tripod).

Sky Tonight (/sky-tonight) is a complete night-sky planning dashboard for your location. It shows: moon phase and illumination, planets visible tonight (with rise/set times and brightness), the dark sky window (astronomical dusk to dawn), Milky Way visibility, active meteor showers, ISS passes for the next 10 days, noctilucent cloud alerts (June and July), upcoming sky events, golden hour times, and photography tips. Everything is calculated for your saved home location.

Check the "Planets tonight" section on the Sky Tonight page. It lists all major planets currently above the horizon with their magnitude (brightness), altitude, and rise/set times. Venus and Jupiter are usually the brightest and easiest to spot even from light-polluted areas.

Solar wind readings (Bz, speed, density) come from Solar1 (SWFO-L1), NOAA's newest satellite parked at the L1 Lagrange point about 1.5 million km sunward of Earth, giving 15 to 60 minutes of advance warning. There are other satellites out there, ACE and IMAP among them, and NOAA switch between them, but Solar1 is the one we stay on because it is the most accurate. If it stops reporting the site falls back to whichever is live and names it on screen, so you always know which satellite you are looking at.

The solar wind data comes from NOAA satellites in space, and now and then NOAA's feed has a short gap, usually a few minutes and occasionally a few hours, while a spacecraft or ground station catches up. When that happens the site is upfront about it: it labels the reading "delayed" and shows how old it is, instead of presenting old numbers as if they were live. This is a gap on NOAA's side, not a fault with the site. It clears on its own the moment fresh data arrives, so you do not need to refresh or do anything. And your headline Hp30 reading comes from a completely separate source (GFZ Potsdam), so it keeps working normally the whole time.

The 3-day Hp30 forecast from GFZ Potsdam gives a rough indication of activity. It is useful for planning but not reliable for specific hours. The real-time Bz and solar wind data is far more actionable. If Bz goes suddenly and strongly negative, that's your cue to go outside right now, regardless of what the forecast said.

The 3D globe shows a rotating Earth with your home pin. You can drag to explore and double-click to set your home location. The globe updates automatically as new data arrives.

Click "Enable alerts" on the Live page and allow browser notifications. You'll get a push notification when geomagnetic activity rises past the threshold you set. You can also enable the sound alert, and a distinctive tone will play through your browser when conditions improve.

The weather card needs your location to work. Tap or click "Use my location" to grant access, or search for your nearest town. Your location is stored in your browser only and is never sent to our servers.

Hp30 index: every 30 minutes. Solar wind (Bz, speed, density): every 1 to 2 minutes via Solar1 satellite, pushed live to your screen via a socket connection. GOES magnetometer: every 2 minutes. Ground magnetometers (substorm detector): checked every 5 minutes, though the observatories themselves publish in batches, so a reading can be up to an hour old and the site tells you when it is. Weather: every 10 minutes.

The sun constantly emits a stream of charged particles, called the solar wind. When this wind carries a southward magnetic field (negative Bz), it reconnects with Earth's magnetosphere, channelling energy into the polar regions. Charged particles spiral down magnetic field lines into the upper atmosphere, exciting oxygen and nitrogen molecules which release light as they relax, and that is the aurora.

Green comes from oxygen atoms at around 100 km altitude releasing energy at a wavelength of 557.7 nm, right in the middle of the visible spectrum where your eyes are most sensitive. Higher up (above 200 km), oxygen produces rare red aurora. Pink/mauve at the bottom edge comes from nitrogen molecules.

A geomagnetic storm is a disturbance in Earth's magnetic field caused by solar wind. Storms are classified G1 (minor) to G5 (extreme). G1 corresponds roughly to Hp30 5, G3 to Hp30 7, G5 to Hp30 9. The G5 storm in May 2024 was the strongest in 20 years and was visible across Europe including southern England.

A substorm is a sudden surge of energy in Earth's magnetosphere, rather like a sudden spark in the magnetic battery. Even when overall storm levels are modest, a substorm expansion can cause the aurora to erupt and brighten dramatically for 30 to 45 minutes. Auroracast monitors ground magnetometers at Uppsala and Lycksele in Sweden and Nurmijärvi in Finland for rapid drops in the horizontal magnetic field of 50 nT or more, which is a reliable signature of a substorm firing. When one is detected, a red alert banner appears on the Live page. Look north immediately. The magnetometer data comes from INTERMAGNET and the institutes that run those observatories.

The sun follows an approximately 11-year cycle of activity. Solar maximum is the peak of that cycle, when sunspot activity and solar flares are most frequent. Solar Cycle 25 peaked in 2024, so we are now on the way down from it. That is not the bad news it sounds like. The years just after a maximum are often excellent for aurora, because coronal holes on the sun send out fast streams of solar wind that sweep past Earth every few weeks, and some of the biggest storms on record have happened on this side of the peak.