How to watch the total eclipse on September 7: The Moon proves flat-Earthers wrong

More than 7 billion people will be able to see with their own eyes that the Earth is spherical. This will happen this September 7th, cloud cover permitting. On the night of Sunday into Monday, a total lunar eclipse will be visible across half of the Earth; and this time, it's unique in that that half will be the most populated part of the planet: all of Asia, Oceania, Africa, and Europe will be able to see at least part of this lunar eclipse. It's during the partial phase that the planet's shadow, projected onto its satellite during a lunar eclipse, takes on a circular shape that belies flat-earthers. Catching this partially eclipsed moon will be one of the great attractions for going out to observe this astronomical phenomenon in Spain.

In almost the entire Iberian Peninsula, the moon will rise completely eclipsed. Thus, the final part of the total eclipse will be visible during the twilight that begins with sunset until the totality phase ends at 8:53 p.m. (Spanish peninsular time). Until then, Palma de Mallorca will have 45 minutes to attempt to see the moon tinged with red: this is how these total eclipses manifest themselves, in which our satellite does not disappear completely, but rather receives a residue of red and orange light that manages to pass through the Earth's atmosphere. In Madrid, this phenomenon will last 18 minutes, and in Oviedo, it will only last 7 minutes. However, at the end of totality, the moon will not yet have risen in Galicia—except in its eastern regions—nor in western Portugal or the Canary Islands, so in those territories the eclipse will only be visible as a partial eclipse.

Time and tips for viewing the total eclipse

The National Geographic Institute provides the schedules for each phase of the eclipse on its website, which ends at 9:56 p.m., and its visibility based on the time of moonrise in Spanish provincial capitals. Experts point out that a lunar eclipse is a phenomenon that can be observed with the naked eye, without the need for astronomical equipment and also without the need for protective equipment such as eclipse glasses, which are essential during a solar eclipse. "Although this is an eclipse that doesn't have ideal viewing conditions in Spain, because the moon has just risen and is still close to the horizon—and so it's easy for buildings, mountains, or sea mist to obscure it—this particularity can also make it more attractive for other reasons, and even more so at this time," says Germán Peris, cultural manager of the Castellón Planetarium.

In Castellón de la Plana, in the eastern part of the country, it gets dark earlier, making the conditions better for observing this particular eclipse. The moon is always full during lunar eclipses, and during this phase, our natural satellite rises just as the sun is setting. Peris encourages the Spanish population to look for an unobstructed spot on the eastern horizon at dusk on Sunday and "starting at sunset in the west, which in Castellón is at 8:20 p.m., try to spot the moon on the opposite side of the sky. As it begins to get dark, it will be easier to observe a slight red hue that characterizes a total lunar eclipse." Under these conditions, this expert prefers to avoid the popular name for these eclipses: "The so-called 'blood moon' can raise expectations that don't correspond to what, with luck, we will be able to see in Spain."

Peris emphasizes that, despite the difficulty of viewing an eclipse so low, "that location, close to the horizon, creates the optical illusion that the moon is much larger; and what's more, anyone with a suitable camera can achieve spectacular photographic compositions of that eclipsed, seemingly gigantic moon next to the landscape." Where the location and weather conditions permit, Peris concludes, "the lunar eclipse on September 7th will be very accessible, occurring at the beginning of a still summer night; and seeing it would be the perfect finishing touch to the holidays for schoolchildren starting school the following day."

Checkmate to flat-earthism

At the other end of Spain, in A Coruña, the chances of seeing the total eclipse are zero. There, astrophysicist Borja Tosar also encourages people to go out and see the phenomenon, "although in our area, when the moon rises, it will already be in the partial eclipse phase. It will still be very interesting to see, because in that final hour of the eclipse, we will go from seeing a small arc of the moon—as if it were very waning—to seeing the full moon: it will be similar to rewinding, in fast motion, what happens in almost 15 days during each lunar cycle."

Tosar highlights the dynamism of this partial phase, which concludes the eclipse: "Those who come to observe the sky, the first few times, are often impatient because everything moves so slowly that it seems to stand still. However, this Sunday we will have the opportunity to appreciate how the moon is rapidly filling up; and also how it is rising, since being close to the horizon, we perceive it better."

During public lunar eclipse observation sessions, this astronomy educator always points out to attendees that they have before them one of the most compelling pieces of evidence that the Earth is spherical: “In the partial phase, we can clearly see that a dark, circular piece is missing: it's the shadow that the Earth casts on the Moon, eclipsing it; and that circular shadow shape would be impossible if our planet were flat. And no, that wouldn't happen even if the Earth itself were circular like a coin; then, we would see its shadow on the Moon as elliptical,” Tosar explains.

An eclipse centered in Asia

Asia, the most populated part of the planet, will be the center of this phenomenon. There, it will be seen as total, and across almost the entire continent, it will coincide in the middle of the night: visible from beginning to end. More than 5.8 billion people—71% of the world's population—will have the possibility of a complete eclipse, if clouds don't block the phenomenon. The phases of a total lunar eclipse occur simultaneously in the half of the world where it is nighttime at that time.

The partial eclipse phase will begin at 6:27 p.m. Spanish mainland time. Although it is still daylight in Spain, the beginning of this phase, in which the full moon appears to have been bitten off, will be visible from New Zealand to Arabia. The total eclipse—when the moon turns red—will begin around 7:31 p.m., with the satellite high in the sky in eastern Asia, and will end at 8:53 p.m., when it reaches its peak over India (while still low above the horizon in most of Spain). The partial farewell phase of the eclipse will last until 9:56 p.m., when the moon will once again regain its normal full moon appearance.

A total of three and a half hours of a lunar eclipse will reach more than 7 billion people—86% of the world's population—at least at some point during these three visible phases. Only the entire Americas, and part of Antarctica, will miss both the partial and total phases of the eclipse, which will be visible as penumbral in the eastern tip of South America and the western tip of Alaska. All lunar eclipses begin and end with a penumbral phase, in which the outer part of the Earth's shadow slightly darkens the Moon, an effect that is still too subtle to be clearly seen with the naked eye.