Total solar eclipse

2019 Jul 2

The Moon will pass in front of the Sun, creating a total eclipse of the Sun visible from South America and Pitcairn between 17:20 and 23:18 BST.

From United Kingdom, no eclipse will be visible.

Eclipse alignment

Solar eclipses occur when the Sun, Moon and Earth are aligned in an almost exact straight line, with the Moon in the middle, such that the Moon passes in front of the Sun.

The Moon passes close to the Sun in the sky every month, at new moon, but because the Moon’s orbit is tipped up by 5° relative to the Earth’s orbit around the Sun, the alignment usually isn’t exact. As a result, the Moon usually passes a few degrees to the side of the Sun.

Even when eclipses do occur, they are not visible from the whole world at once. The Moon casts a circular shadow onto the Earth, but because the Moon is much smaller than the Earth, the shadow doesn’t cover the whole planet. Over time, the shadow sweeps across the Earth, so that different places see the eclipse at different times.

The eclipse path

The total eclipse will be visible from Argentina, Chile, Pitcairn and Uruguay.

Additionally, a partial eclipse will be much more widely visible, from countries including:

Country Percentage of
Sun covered
Brazil 96%
French Polynesia 90%
Paraguay 83%
Bolivia 82%
Peru 71%
Falkland Islands 53%
Cook Islands 43%
Ecuador 41%
Kiribati 24%
Colombia 23%

As seen from any given location, this total eclipse will last for a maximum of 4 minutes.

Eclipse safety

The geometry of a solar eclipse

Solar eclipses take place when the Earth moves through the Moon’s shadow. The dark gray cone behind the Moon indicates the region of space in which the Moon appears to completely cover the Sun’s disk (the Moon’s umbra). The light gray area around it shows where the Moon appears to partially cover the Sun’s disk (the Moon’s penumbra).

Observing the Sun can be very dangerous if it is not done with the right equipment. The Sun is the brightest object in the sky, and looking directly at it can cause permanent eye damage within seconds. Viewing it through any optical instrument – even a pair of binoculars or the finderscope on the side of your telescope – can cause instant and permanent blindness.

If you have any doubts about whether your equipment is safe, it is best not to risk using it. By far the safest thing to do is to go along to a public observing event. Many astronomical societies are likely to be hosting observing events on the day, and they’ll be sure to welcome newcomers. You may meet some new people at the same time as seeing the transit.

Many astronomy suppliers sell special special filters which are made for safe solar viewing. These include aluminised mylar filters, or black polymer filters, identified as suitable for direct viewing of the Sun. Check that the filter has a CE mark, and a statement that it conforms to European Community Directive 89/686/EEC. Alternatively, you can use a welder’s glass rated at No. 14 or higher. Always read the manufacturer’s instructions carefully.

Never attempt to make your own filter. In addition to visible light, the Sun also produces prodigious amounts of infrared and ultraviolet radiation which cannot be seen yet can still damage your eye. Even if a homebrew filter appears adequate, it may allow this unseen radiation to pass.

This entry in the observing calendar was provided by In-The-Sky.org

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