Moon worshippers are in for a treat this Sunday, as they'll get to witness a rare lunar eclipse during an extra big harvest moon.
Albertans will see the total lunar eclipse should they happen to look at the moon anytime after 8:11 p.m. Sunday.
The celestial event coincides with the full moon closest to the fall equinox (which was last Wednesday), making this moon a harvest moon.
And it's happening when the moon will look up to 14 per cent bigger than normal, making it a supermoon.
This is the fourth total lunar eclipse in two years that's been visible from Alberta, said Frank Florian, space sciences director at the Telus World of Science in Edmonton. We won't get another tetrad of eclipses like this until around 2032, and just one of those eclipses will be visible from Edmonton.
A solar eclipse is when the moon passes between the Earth and the sun, said St. Albert astronomer Murray Paulson. That makes them tough to spot – the moon is relatively small, and the shadow it casts can be seen only within a 100-kilometre wide strip or so of the Earth's surface.
A lunar eclipse is when the Earth overshadows the moon, he continued. Since the Earth is huge compared to the moon, these events are much easier to spot.
"Anybody anywhere on that side of the Earth that doesn't have a cloudy sky will be able to see it."
According to NASA, this particular full moon is considered a supermoon in that it's happening when the moon is at its perigee, or its closest point to Earth in its orbit. This makes it look about 14 per cent bigger than it does at its apogee, or farthest point from the Earth.
Florian said the average person wouldn't notice the difference, as the size change is very small.
NASA reports that we've only had a supermoon coincide with an eclipse five times since 1900, and won't have another supermoon eclipse until 2033.
The Harvest Moon is so called because it happens around harvest time, Paulson said. Many farmers use its light to work long into the night to get their crops in more quickly.
Blood red moon
The moon will start getting darker starting in the lower left at around 7:07 p.m. as it enters the Earth's penumbra, or the diffuse edge of its shadow, Florian said. We won't see that here, as the moon won't be above the horizon in Edmonton until 7:16 p.m.
The darkness will fully engulf the moon by 8:11 p.m., which is when it will be totally within the darkest part of the Earth's shadow, the umbra.
At that point, the only light reaching the moon will be that which is refracted through the Earth's atmosphere, Florian said. The blue light gets scattered, leaving only longer red wavelengths, making the moon look blood red.
If you were standing on the moon looking back at the Earth at that time, you'd see the edge of the dark side of the planet rimmed with the red of every sunrise and sunset at once, Paulson said.
"It would be glorious!"
The eclipse will last a full 72 minutes, after which the moon will unveil itself starting from the left, Florian said. The moon will be back to normal at 10:27 p.m.
The Telus World of Science observatory will be open to the public starting at 6:30 p.m. Sunday for those wanting to catch the eclipse, Florian said. Guests will also be able to use smaller telescopes set up outside. Binoculars or your eyeballs will also work.
Paulson encouraged everyone to go out and see the eclipse Sunday.
"It's a rare chance to see a wonderful phenomenon."
The next total lunar eclipse visible from Edmonton will be on Jan. 31, 2018.
