Observation guide

Eye safety comes first

Looking at the Sun without proper protection can permanently damage your eyes, even when most of the Sun is covered. The retina has no pain receptors: you will not feel the injury while it happens.

The rules below follow the recommendations of NASA and of the American Astronomical Society (AAS).

• Use solar eclipse glasses or a handheld solar viewer that complies with the international standard ISO 12312-2, bought from a reputable supplier. The AAS maintains a list of reputable vendors.
• Check them before use: discard any glasses that are scratched, torn, punctured or whose filter is separating from the frame.
• Ordinary sunglasses are never safe, however dark they are. Neither are smoked glass, exposed photographic film, CDs, X-ray films or welding glasses that do not reach shade 12–14.
• Never look through a camera, binoculars or a telescope while wearing eclipse glasses: the concentrated sunlight will burn through the glasses and into your eye. Optics need their own certified solar filter, mounted on the front of the instrument (on the side facing the Sun), never at the eyepiece.
• Supervise children at all times while they use solar viewers.

When can you look with the naked eye?

Only during totality, and only from inside the path of totality. When the Moon hides the very last bright point of the Sun, you can take off your glasses and look at the corona with the naked eye. If you still see any part of the bright Sun through your glasses, totality has not started.

Put your glasses back on as soon as the first bright point of sunlight reappears (the “diamond ring” at the end of totality). Use the calculator to know the exact times for your location — and set an alarm a few seconds before the end of totality.

Outside the path of totality — in Tunis, Sousse, Monastir, Bizerte or Médenine for example — the Sun is never completely covered. You must keep your eye protection on during the whole eclipse. A thin crescent of only 0.1 % of the Sun is still dangerous.

No glasses? Use projection

You can watch the partial phases indirectly by projection: a pinhole in a piece of card, a colander or the gaps between the leaves of a tree project small images of the crescent Sun onto the ground. Always keep your back to the Sun and never look at the Sun through the pinhole.

If you think your eyes have been injured

Blurred vision, a dark spot or distorted vision after looking at the Sun require a prompt consultation with an ophthalmologist.

The phases of a total solar eclipse

1. First contact (C1) — the Moon starts to cover the edge of the Sun. The partial eclipse begins; nothing changes in daylight at first.
2. Partial phase — the crescent of the Sun becomes thinner over about one hour and ten minutes. Shadows of leaves become small crescents. In the last 15 minutes, the light turns strange and metallic, the temperature can drop noticeably and the wind may change.
3. Just before totality — shadow bands may ripple across light-coloured ground; the dark shadow of the Moon rushes in from the west. The last rays of the Sun shine through the lunar valleys: these are Baily’s beads, followed by the diamond ring.
4. Second contact (C2), totality — the Sun is completely hidden. The pearly solar corona spreads around the black disk of the Moon; pinkish prominences may be visible at its edge. The sky becomes dark blue to deep twilight and a “sunset” glow surrounds the whole horizon.
5. Third contact (C3) — the diamond ring appears on the other side of the Moon: glasses back on immediately.
6. Fourth contact (C4) — the Moon leaves the solar disk; the eclipse is over.

What to look for during totality on 2 August 2027

Computations for Sfax at maximum eclipse (10:11 Tunisian time) show that Venus will be very close to the Sun, less than 3° away, and very bright; Mercury will be about 10° from the Sun and Jupiter about 22°, all three in the east-southeast part of the sky, above the Sun. The bright star Sirius will be about 38° above the southern horizon. How many stars and planets you will see depends on the darkness of the sky, which varies with the duration of totality and the transparency of the air.

Partial eclipse or total eclipse: a world of difference

A partial eclipse, even at 97 % as in Tunis, remains a daylight phenomenon: the remaining crescent is still dazzling and the sky stays blue. Only totality reveals the corona, darkens the sky and turns day into night for a few minutes. This is why a short trip into the path of totality is worth it: from Sousse, Monastir or Tunis, the path is less than an hour to a couple of hours away by road.

What is special about the eclipse of 2 August 2027

• It belongs to Saros series 136, which also produced the very long eclipses of 1955 and 1973.
• Its maximum duration reaches 6 min 23 s in Egypt, near Luxor (greatest eclipse according to NASA), which places it among the longest total eclipses of the century.
• In Tunisia, totality lasts up to about 5 min 45 s on the central line, with the Sun high in the sky (about 53–56° above the horizon), in the middle of a summer morning.

Recommended equipment

• One pair of ISO 12312-2 eclipse glasses per person, plus spare pairs.
• For binoculars, telescopes and cameras: certified white-light solar filters designed for the instrument, fixed securely on the front.
• A hat, sunscreen, light clothing and plenty of water: on 2 August, temperatures around 10:00 are typically close to 30 °C on the coast and higher inland.
• A folding chair or mat, a watch or phone set to the exact time, and the list of contact times for your site.

Mistakes to avoid

• Taking off your glasses too early, while a thin crescent is still visible, or putting them back on too late.
• Using unchecked or homemade filters, or glasses without ISO 12312-2 marking from an unknown supplier.
• Spending the whole totality behind a camera or phone screen: plan photos in advance and keep at least one minute to simply look.
• Arriving at the last minute: traffic may be heavy on the morning of the eclipse. Plan to be on site at least an hour before first contact.
• Choosing a site exactly at the edge of the path: near the limits, a few kilometres make a difference of minutes.

Photographing the eclipse

• During the partial phases, a solar filter is required on the front of the lens (white-light filter of optical density 5, sometimes sold as “ND 100000”). Without it, you risk damaging both the camera sensor and your eyes.
• Remove the filter only during totality, then put it back at third contact.
• Use a tripod, manual focus set on the Sun beforehand, and bracket the exposures during totality: the corona has a very wide range of brightness.
• Disable the flash — it is useless and disturbs other observers.
• Smartphones can capture the atmosphere of totality (the horizon, people, the darkness) very well; for the partial phases, hold a certified solar filter in front of the lens.
• Rehearse with your equipment a few days before, at the same time of day.

Practical tips for observing outdoors in August

• Heat: the eclipse takes place in the middle of the morning in midsummer. Protect yourself and children from the sun and dehydration, especially in the south and inland.
• Respect sites and residents: ask for permission on private land, do not leave waste behind and follow the instructions of local authorities.
• Travel safety: some mountainous and border areas are subject to official travel warnings; check your government’s travel advice and local regulations before choosing a remote site.
• Weather: see our weather and climate page — morning skies are usually clear, but dust can reduce visibility.