Total lunar eclipses are certainly more common than total solar eclipses.

In fact, for any given spot on Earth you only get one total solar eclipse every 360 years. You get a total lunar eclipse for any given place once every two to three years and sometimes more frequently than that.

We haven’t had a total lunar eclipse since February of 2008 and we’re not due for another one until 2014, so they haven’t been all that common around here lately.

So if you want to take in all the beauty of a complete lunar cover up, don’t waste your chance this coming Tuesday morning.

I know you’ll lose sleep, but a lot of astronomical phenomena are coming together right now.

Not only is the lunar eclipse happening on the longest night of the year, but it begins right around the time when the full moon achieves its highest point in our Butler sky for 2010.

The sun and the moon are at opposite ends of the sky during any full moon. That’s why the moon takes such a high arc across the sky in December. It’s taking the same high arc in the heavens that the sun does on the first day of summer at the opposite end of the year.

Conversely, the full moon takes the same low arc across the sky around the first day of summer as the sun takes across the heavens this time of the year.

Lunar eclipses occur when the Earth is nearly in a straight line between the sun and the moon and the moon slips into the Earth’s shadow, as you can see in the diagram.

The Earth doesn’t have to be in an exact line between the sun and the moon because at the distance of the moon the Earth’s umbra shadow is just over 5,500 miles wide.

Since the moon is less than 2,200 miles in diameter, getting into the Earth’s shadow isn’t a huge accomplishment. There’s plenty of the Earth’s shadow to go around.

We don’t have a lunar eclipse every full moon because the moon’s 27.3 day orbit around the Earth is tilted by five degrees in respect to Earth’s 365 day orbit around the sun. Because of that, during most full moons, the moon misses the Earth’s shadow.

This time around, however, the full moon is full at one of the two points where the moon’s orbital plane intersects the Earth’s orbital plane: The right place at the right time for a total lunar eclipse

Right around 12:33 a.m., early Tuesday morning, the moon will be shining over the head of the mighty constellation Orion the Hunter. Right about then you’ll start to see a dark notch beginning to grow on the left side of the lunar disk.

You can’t help but notice that the shadow has a circular edge to it as it creeps across the lunar surface, visual proof that the Earth is indeed round because of the circular shadow.

From 1:41 a.m. until 2:53 a.m. the moon will be totally eclipsed but will still be visible. It could take on a bright orange hue or it might be bloody red.No one can really predict what hue the eclipsed moon will take on. Only the shadow knows. The Earth’s umbra shadow that is.The umbra shadow opposite the sun is not totally dark because some of the sun’s light manages to get through our Earth’s atmospheric shell as you can see in the diagram.The sunlight that does get through is bent and strained as it comes through our atmosphere. All the blue and yellow components of the sun’s light are scattered away, leaving just the reddish part of the sun’s light that bathes the eclipsed moon. The shade of the red light reaching the moon depends on the combined atmospheric conditions of where the sunlight passes through on its way to the moon.That makes it impossible to know exactly what shade of red or orange the eclipsed moon will take on, but it’s also part of the fun of a total lunar eclipse.No matter what shade of red the moon takes on, it will be beautiful and perfectly safe to look at. You don’t have to look through any special glass or anything.An occasional gander through a telescope at the eclipsed moon is nice, but I think it’s a wonderful experience to watch it with just your natural eyesight or maybe a pair of binoculars. You want to take in as much as of the eye candy as you can!With a telescope during totality you’ll see the moon pass in front of or eclipse several stars.Not only does the moon travel east to west across the sky, but it also takes a much slower eastward migration among the background of stars as it orbits the Earth. Normally it’s hard to see these stellar eclipses because of the brightness of the moon, but with the moon going through a 72 minute “power failure,” they’re a lot easier to see.Also, because the moon has no atmosphere, you’ll see stars popping out of view on the eastern side of the moon’s disk and popping into view on the western side.So early Tuesday morning say goodbye to this autumn of 2010 with the last total lunar eclipse until 2014. Later that Tuesday evening at 5:38 p.m., winter officially begins at the exact moment of the Winter Solstice. Days start getting longer again!Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Pennsylvania Starwatch,” available at bookstores and at www.lynchandthestars.com

Diagram of what happens during a lunar eclipse