Blue moon rising this weekend

Skywatchers will get a rare treat on Halloween, with a blue moon expected to appear Saturday.

The Halloween blue moon is so rare, you can say it happens even less than once in a blue moon.

A blue moon is described as being the second full moon to fall within the same month. Blue moons are seen roughly every two and a half years — which explains the poetic phrase to describe a rare event.

But a blue moon only falls on Halloween every 18 to 19 years. The last one was Oct. 31, 2001,, although it was only visible to Central and Pacific time zones, according to the Farmer’s Almanac.

This is the first time a Halloween blue moon will be visible to all time zones since 1944.

Despite its name, the moon will not look blue, but its usual white glow.

Simon Smith, a regular stargazer, says he plans to sit on his porch Saturday night and catch the view.

“I try to keep an eye out for full moons,” Smith said.

“They make stargazing harder, but the full moon is so lovely in its own right that it deserves a bit of celebration every 28 days.”

The first full moon this month took place Oct. 1.

Michael Reid, an associate professor in University of Toronto’s department of astronomy and astrophysics, told the Star that on average, there are 12 full moons in a year.

The Halloween blue moon will be a “mini-moon,” meaning it is the farthest from the Earth in its orbit.

Although the moon is technically further away, the size change cannot be seen with the naked eye.

A full moon is seen when the sun and the moon are on opposite sides of the Earth.

Once a month, this causes the light of the sun to fully illuminate one side of the moon.

“A true full moon is just an instant. The moon is constantly moving, so the exact moment when it’s opposite the sun is the instant of full moon,” Reid said.

Since the “true” blue moon will happen during the day Saturday, at10:49 a.m., it will not be visible.

But Reid says you will still be able to see the moon on Halloween night in Toronto.

“For the average person who doesn’t care about seeing it at the exact instant when it’s full, just go out when it’s dark.”