Denver Public Schools

Steele Planetarium

About our Planetarium


We are located at:
320 So. Marion Parkway
Denver, CO 80209

Ralph Sodano


December: A Bloody Moon for the Longest Night.

The winter solstice arrives on December 21st with a special treat for Colorado … a total lunar eclipse! But first the solstice...

There are actually two solstices. In the southern hemisphere they will be celebrating the summer solstice. At 40 degrees latitude south in the city of Viedma, Argentina, the citizens there will enjoy the longest day of the year: fifteen hours of daylight and only nine hours of night.  At the very same time in Denver, located at latitude 40 degrees north, we will be celebrating the winter solstice. Hunkering down under wool caps and down coats, we’ll be bracing ourselves for a mere nine hours of sunlight and the longest night of the year, fifteen hours.  Just the opposite of Viedma. What happens next is counter-intuitive. About two weeks after the solstice on January 3rd our Earth will make its closest approach to the sun or, perihelion. While we in Denver will be shivering and huddling for warmth, we’ll actually be the closest that we’ll be to the sun all year! By the same token, we’ll be the furthest from the sun in Denver on July 4th some two weeks after our summer solstice.

The key to our seasonal climate changes is not our distance from the sun but the 23½  degree tilt of the earth on its axis. When our respective hemispheres are tilted toward the sun we get longer days with more direct sun rays. What’s so special about direct sun rays? First of all they’re more focused, less spread out, they are more perpendicular in striking the Earth’s surface. So more solar energy is concentrated in a smaller area. Second, direct sun rays travel a shorter path through our atmosphere so less energy is lost before it reaches the ground.

When a hemisphere is tilted away from the sun just the opposite happens. Sun rays not only loose more energy traveling through a greater cross section of atmosphere but then having reached the surface at a greater angle, a lesser amount of energy must now spread out and warm a larger surface area.

Now, about that total lunar eclipse. For Denver the lunar eclipse will start on the evening of December 20th with a full moon. As third grade teachers who are instructing the Objects In The Sky Unit should point out to their students, a lunar eclipse always starts out with the full moon phase.  This is where the sun, Earth and moon are lined up in a straight line.  You may have noticed as a full moon rises in the eastern sky, the sun has just set in the west.

It takes about 27 ½ days for the moon to complete an orbit of the Earth. Due to some lousy celestial choreography, It takes an additional couple of days for the moon to go from full moon to full moon phase. If the moon orbited the Earth in the exact same plane as the Earth’s orbit about the sun, we’d get a lunar and solar eclipse each and every month somewhere on the earth. But the moon’s orbit is inclined some 5 degrees relative to the Earth’s orbit about the sun. So most the time the full moon is just above or just below the Earth’s orbital plane, successfully dodging our planet’s shadow.  Only a few times a year does the full moon cross directly behind the Earth with our planet’s shadow dragging across its face.

Here in Denver at about 11:30 P.M. Mountain Standard Time, we’ll see the first dimming of the moon. The next stage will test the night owl in all of us as we must wait until 12:41 A.M. for the beginning of the total eclipse.  Mid eclipse will finally occur at 1:17A.M. with totality ending at 1:53 A.M.   For those of you who really want to test the character of your will power, the strength of your espresso maker and the severity of your insomnia (or all three), you may try and stay up until 3:01 A.M. for final moments of the eclipse.

If the Earth did not have an atmosphere the moon would be totally lost in the shadow of our planet.   But during totality the moon may appear in color from coffee to copper to down right bloody. Where does all his color come from?  From every lovely sunrise and sunset on Earth. Our planet’s atmosphere filters out all the shorter wavelengths of sunlight and bends the longer wavelengths to soften the bleak darkness of the earth’s shadow on the moon. As you stand cold and shivering  with the icy fingers of the winter solstice passing through you, realize that some of the warm hues cast upon the moon in the far distance are from tropical shores elsewhere right here on the earth.

Use the "" link on the upper right side of this page to get all your current updates on the eclipse and other celestial events.

 Please contact me via e-mail ( or phone (720.424.3761) with any questions about our programs or to sign up a program for your students.

Good viewing!

Ralph Sodano



This page was last updated: Friday, December 17, 2010 at 3:58:55 PM