C1, C2, C3, C4: the eclipse contacts, explained
A total eclipse has four contacts and a maximum, and only one of the stretches lets you look without a filter. In Ceuta the partial eclipse begins at 09:40, totality runs from 10:45 to 10:50, and everything is over by 12:01.
Published 17 August 2026
A "contact" is simply the instant when the edges of the solar and lunar discs touch. There are four of them, and numbering them is how astronomers avoid saying the whole sentence every time. They are worth learning because they are what will appear in every programme of events, every app and every conversation that day.
C1 · First contact
At 09:40 the Moon touches the Sun's edge for the first time. Nothing is noticeable: a tiny notch appears that you can only see through a filter, and daylight is unchanged. This is when the eclipse glasses go on and stay on until C2. Over the next hour the bite grows slowly and, towards the end, the light turns strange — not darker so much as metallic, with unusually sharp shadows.
C2 · Second contact: totality begins
At 10:45 the lunar disc covers the solar one completely. In the seconds before, two things happen that you have to look for deliberately: shadow bands, faint ripples running across pale ground, and Baily's beads, the last points of light squeezing through valleys on the lunar limb until one remains — the diamond ring. There, and only there, the filters come off.
Maximum eclipse
At 10:47, halfway through totality, the centre of the lunar disc passes as close as it will get to the centre of the solar one. Nothing visible marks the instant: it is a computed figure, useful for knowing that you are halfway and have as long again ahead of you.
C3 · Third contact: totality ends
At 10:50 the first flash of Sun reappears on the opposite side. This is the dangerous moment of the day, because your eye is dark-adapted, the pupil is wide open and the blink reflex arrives too late. The glasses go on at the first hint of light, not when it starts to hurt.
Which is why you should not trust the clock
C4 · Fourth contact
At 12:01 the Moon leaves the solar disc and the eclipse is over. Hardly anyone stays that long, and that is fine: what follows C3 is the same film in reverse. What is worth doing is staying put a while longer, because the mass exit towards the ferry or the road is the worst part of the day.
The pocket summary
| Contact | Local time | What to do |
|---|---|---|
| C1 · partial begins | 09:40 | Filter on |
| C2 · totality begins | 10:45 | Filter off, once no Sun is visible |
| Maximum | 10:47 | Halfway through totality |
| C3 · totality ends | 10:50 | Filter on at the first flash |
| C4 · partial ends | 12:01 | Filter until the end |
Frequently asked questions
When can I take the eclipse glasses off?
Only between C2 and C3 — that is between 10:45 and 10:50 in Ceuta — and only while the solar disc is completely covered. At every other point in the eclipse a certified filter is required.
What is the diamond ring?
The last point of sunlight still visible just before C2, or the first to return at C3, already surrounded by the glow of the corona. It lasts a second or two and is one of the most remembered moments of the whole event.
How long does the whole eclipse last?
In Ceuta, from C1 at 09:40 to C4 at 12:01: a little over two and a half hours in all, of which 4 minutes and 48 seconds are totality.
The illustrations are our own, and any figures shown in them come from the same Besselian computation as the tables elsewhere on the site. Sources and method