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The lunar Eclipse of a Blue Moon

The term Blue Moon originally refered to an occurrence that was very rare, such as a Moon that truely appeared blue in colour, but it has now become a name for the second full Moon in one month.

Local Astronomer Wayne Holmes has had an interest in astronomy since he got his first telescope and began reading about the objects in the sky at a young age. As the coordinator of the Starry Nights program at Taghum Hall as well as multi session astronomy classes as part of the Learning in Retirement program and astronomy programs for schools, Holmes has always had a desire to sky gaze. Thankfully, Holmes has agreed to share his knowledge in this column, Solar System and Beyond that will appear occasionally in The Nelson Daily.

We started the year off with a full "Super Moon" on January 1st and we will end the month with the second full Moon of January, what some call a "Blue Moon".

The term Blue Moon originally refered to an occurrence that was very rare, such as a Moon that truely appeared blue in colour, but it has now become a name for the second full Moon in one month. Although uncommon, a month with two full Moons is not that rare. March of this year will be another month with two full Moons. What makes this "Blue Moon" unusual is that Earth will temporarily block the Sun's light from the Moon, creating a lunar eclipse that may turn the "Blue Moon" red.

Some people are calling this another "Super Moon" however it will be 27 hours past perigee, (the closest distance from Earth). The January 1st Moon was closer, in fact the closest the Moon will be for the year, making it a true "Super Moon".  

The eclipse happens early in the Morning of January 31st and is the first lunar eclipse visible to us since September 27th 2015. All you need to see this event is a relatively low western horizon........and clear skies. No special glasses or telescopes are needed, although watching the eclipse through binoculars would be fun.

Earth's shadow has two parts. The penumbra is partial shadow and as the Moon passes through the penumbra it is dimmed, but only slightly. What you want to watch for is the Moon passing through the darker shadow, the umbra. This is the shadow that results when the Earth is completely blocking the Sun's light from reaching the Moon. Some Sun light is refracted through Earth's atmosphere and it is this bending of Sun light through the atmosphere that gives the eclipsed Moon it's reddish hue. If we were to witness the eclipse from a point on the Moon we would see Earth's atmosphere glowing red, illuminated from behind by the Sun.

To see the start of the umbral phase of the eclipse, start looking at the Moon around 3:45 am. Little by little you will see Earth's shadow creep across the Moon. The top left hand side of the Moon is the first to enter Earth's shadow. By 4:51am the Moon will be completely inside the umbral shadow and should appear copper colour.

The southern part of the Moon may appear slightly brighter due to the Moon's path through the umbral shadow being a little lower than dead center. By 5:29 am the eclipse will be at mid-totality and the Moon will be at it's darkest. Remaining in the umbral shadow, the Moon will slowly move toward the eastern edge of the umbra until finally at 6:08 am it enters the penumbral shadow and begins to brighten.

By this time it should be quite low on the western horizon and mountains may make viewing the final minutes of the eclipse a challenge.  

Wayne Holmes