It’ll be only for a few minutes and you’ll have to get up very early to catch sight of it in the skies above Calgary, but if you don’t, your next chance won’t be for another 100 years.

A total lunar eclipse is scheduled to take place for just five minutes, around 4 a.m. on Saturday morning.

It’s when the Earth, sun, and moon are in perfect alignment, blotting out most of the blue light from the sun and giving the moon a distinct red shade.

It’s more commonly known as a ‘Blood Moon’.

Experts say it’s a once in a lifetime opportunity. “The alignment tonight and really tomorrow morning will be perfect such that the moon will pass into the Earth’s shadow and fall into darkness,” says Roland Deschesne, of the Ritak Astronomical Society in Vulcan, Alberta.

NASA says total lunar eclipses are less common, but one lasting just five minutes is rarer still.

Officials say that the next time a total lunar eclipse of such a short duration will happen won’t be for another 100 years.

Astronauts will also be available on Twitter to answer questions about the event.