Eclipse of 12 August: in Ticino the Sun will be 92% covered

The solar eclipse of 12 August will be total from Spain and only partial in Ticino. The event will begin just before 7.30pm and reach its maximum around 8.17pm, when the Moon will cover about 92% of the Sun.

At our latitude the problem is the timing. By then the Sun is already close to setting, and a spot with a clear horizon to the west is needed, preferably at altitude.

The shape of the terrain complicates the search, because the mountains cut off the horizon in exactly the useful direction. For this reason the Aldo e Cele Daccò solar research institute is organising a dedicated event with the Cardada cable car company, including special ascents. Registration is compulsory.

Why only one band sees totality

Renzo Ramelli, deputy director of the institute, explains that the Moon is relatively close to Earth and casts a shadow that does not cover the whole planet at once. This produces a band of totality about a hundred kilometres wide.

This time the band starts at the Arctic ice cap, crosses Greenland and Iceland and reaches Spain and Majorca just before sunset.

The difference between partial and total is not one of degree. During the total phase, «quando la Luna copre completamente la fotosfera, diventano visibili gli strati più esterni dell'atmosfera solare, in particolare la corona, che normalmente non vediamo perché è circa un milione di volte meno luminosa della fotosfera» ("when the Moon completely covers the photosphere, the outermost layers of the solar atmosphere become visible, in particular the corona, which we normally do not see because it is about a million times less bright than the photosphere"), Ramelli says. At that moment scientific measurements become possible that are otherwise ruled out.

Anyone observing must nonetheless use certified glasses. «Non bisogna improvvisare: anche se il Sole è parzialmente coperto, la luce può danneggiare la vista in modo permanente» ("You must not improvise: even when the Sun is partly covered, the light can damage eyesight permanently"), the researcher warns.

Safe alternatives exist. A telescope can project the solar image, or a simple pinhole can cast the image onto a surface. A colander, a grater or a punctured piece of card work the same way. The glasses may only be removed during totality, and that moment will not arrive in Ticino.

The evening offers a second event. The Perseids peak on the same night and this year coincide with a new Moon, so without the moonlight that usually interferes with watching meteors.

Anyone who misses it will have to wait until 2 August next year. That eclipse will be total in Andalusia, North Africa and Saudi Arabia, and in Ticino once again only partial, in the late morning.