Third contact (C3) — the end of totality
Third contact is the moment the Moon's trailing edge reaches the near limb of the Sun and the total or annular phase ends. Sunlight returns instantly.
Third contact, C3, is the instant the Moon's trailing edge reaches the near limb of the Sun — internal tangency again, on the side the Moon entered from, which is why the light returns opposite the point where it vanished. Totality or annularity ends here and the partial phase resumes.
It arrives faster than it feels
The return of sunlight at C3 is genuinely abrupt. One bead of photosphere appears at the Moon's edge and within a second or two the corona is washed out and the sky is bright again. People consistently misjudge how much time they have; the standard advice is to stop looking at the clock in the last thirty seconds and simply watch, because the end announces itself.
Filters go back on at the first hint of returning light, not after it. The photosphere is at full brightness the moment any of it is showing, and the eye is at its most dilated after minutes of darkness — this is the most dangerous moment of the whole eclipse.
C2 and C3 as a pair
The two are the honest edges of totality, and this app treats them as a unit: the countdown runs to C2, and then to C3. Their separation is the duration, and it is the number that decides whether a location is worth travelling to. Near the limits of the path they close up to almost nothing; on the centre line they are as far apart as that eclipse can make them at that point along the path. The longest totality of all is near greatest eclipse.
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Updated 13 August 2026.