The first total solar eclipse visible from continental Europe in twenty-seven years, watched one August evening from a lookout north of Logroño, in La Rioja — the pictures are in the photo album. Planned with PeakFinder to make sure no ridge hid the western horizon, and with the IGN eclipse viewer — official open data — for the amount of obscuration and local timings. The Sun, very low over the western horizon, was eclipsed right at sunset.
Why total eclipses are a lucky coincidence
That the Moon can exactly cover the Sun is close to a miracle: the Sun is roughly 400× wider than the Moon, but also roughly 400× farther away, so both appear about the same size in the sky — an alignment unique in the Solar System. And it is slowly drifting apart: the Moon recedes from Earth by ~3.8 cm per year, so in a few hundred million years total eclipses will no longer be possible. We live at the right time.
How the dates are computed
An eclipse can only happen at new moon, but not every new moon produces one. The Moon's orbit is tilted ~5° to the ecliptic, so it usually passes just above or just below the Sun. An eclipse requires the new moon to occur while the Moon is near one of the two points where its orbit crosses the ecliptic plane (the nodes). These two nodes drift, and their alignment with the new moon recurs in a wonderful beat called the Saros cycle: 223 synodic months equal almost exactly 242 draconic months, so the Sun–Earth–Moon geometry repeats every 18 years and 11 days. Today's eclipse is the legacy of one 18 years ago, and a sibling will return in another 18 — shifted a third of the way around the globe.
Proper predictions use the Besselian elements published by NASA/GSFC: a set of seven polynomials describing the Moon's shadow cone, enough to compute location-specific contact times, magnitude and obscuration — the numbers that drove the IGN viewer used for this trip.
Worth chasing next
- 2 Aug 2027 — the great one: ~6 min 23 s of totality near Luxor, Egypt, the longest over land for the rest of the century. Path crosses southern Spain, North Africa and the Middle East.
- 22 Jul 2028 — total over Australia, ~5 min 10 s at maximum, passing close to Sydney.
- 25 Nov 2030 — total over Namibia, Botswana, South Africa and southern Australia, ~3 min 44 s.
- 20 Mar 2034 — total from Nigeria to China via Chad, Sudan, Egypt and Saudi Arabia, ~4 min 9 s.
- 12 Aug 2045 — the US comes back with a coast-to-coast totality, California to Florida, over 6 min.