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December Star Map

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A Holiday Mars Invasion!

There’s magic in the air this holiday season, and an extra gift from the heavens as Mars invades our evening sky. On November 30th, Mars and Earth achieved their closest approach to each other, a little over 50 million miles away. Earth and Mars catch up in their orbits around the sun and achieve minimum separation every two years and two months. On December 8th, the Earth and Mars will be in what astronomers call opposition. That’s when the Earth is in a line between Mars and the sun. The two planets aren’t quite as close to each other than but close enough, a little over 51 million miles separating them. If both the Earth and Mars orbited the sun in perfect circles in the same exact plane, Earth and Mars would be at their minimum separation on December 8th and not November 30th. For that same reason, not all opposition distances are the same. Some are much closer than others. Two years ago Mars was less than 39 million miles away.

During opposition Mars and the sun are on opposite sides of the sky. Just like a full moon, Mars rises at sunset and sets at sunrise so it’s available for us to look at all night long. This month Mars is the second brightest star-like object in the evening sky. Only Jupiter is brighter. As you watch Mars rise in the east, you can easily see why it’s called the red planet.

Mars is a prime target for even small telescopes in December. It really helps to let Mars get high in the sky so it’s above the thicker layer of Earth’s blurring atmosphere near the horizon. That means staying up as late as you can to observe Mars. Take long, continual views of Mars or any other planet, so your eye can adjust to the light level in the eyepieces. That also helps you catch clearer views through less turbulent patches in our atmosphere as they pass by.

One of the easiest surface features to see on Mars is the northern polar cap. With most telescopes, you see an inverted, upside-down image. If that’s how it is with your scope, the polar cap will appear as a white smudge on the lower side of the disk of Mars. It can still be tricky to see, however. As Mars rises, the polar cap will appear on the lower right edge of the planet, then gradually shifts to the bottom of the disk as Mars reaches its highest point in the sky overnight. You may also see dark patches that are mainly the extensive valleys and extinct volcanos on Mars. Let’s keep our fingers crossed that there won’t be a global dust storm on Mars during this time. That can happen! On December 7th, the night before opposition, the nearly full moon will be incredibly close to Mars in the eastern heavens. In fact, for most of North America the moon will eclipse Mars in the early evening, what astronomers call an occultation. In the Twin Cities the moon will be covering up Mars from just after 9pm to just after 11pm. For other locations check out my favorite stargazing app, Sky Guide.

The planets Jupiter and Saturn are also great telescope targets this month. You can see Jupiter’s brighter moons and cloud bands and enjoy Saturn’s wonderful ring system and some of its moons even with a small telescope. Both planets are still worth your time with the telescope, although they may not be quite as sharp since their distances from Earth are increasing. Saturn is also getting closer to the horizon with its blurring effects. The elusive planet Mercury will put in a appearance the last half of this month. It’s a very poor telescope target but it's fairly easy to see as a moderately bright naked “star” in the early evening twilight in the very low southwestern sky. Don’t wait too long to look for Mercury because by about an hour after sunset it slips below the horizon. The much brighter planet Venus isn’t all far away from Mercury but is much closer in the sky to the setting sun and lost on its glare. In January Venus will be making a much grander entrance in the early evening.

The full moon this month, popularly known as the Cold Moon, is on December 8th. That’s too bad, because during the annual Geminid meteor shower December 13-14th, one of the best of the year, there will still be a lot of interfering moonlight with the waning gibbous moon rising around 9 pm. Despite that, the Geminids are such a prolific shower you should be able to catch at least some meteors, especially away from light pollution in the countryside.

Later this month, there’ll be another meteor shower, the Ursids, peaking the night of December 21st-22nd. There won’t be any competing moonlight, but this is a minor meteor shower producing only around 10 to 15 meteors an hour. It’s still worth a look-see.

The long December night skies are blessed with some of the brightest constellations of the year, more than worth bundling up for. The great horse Pegasus is riding high in the south-southwestern sky with Cassiopeia the Queen, looking like a bright “W”, in the high northern sky. The Big Dipper, the rear end and tail of the constellation Ursa Major, or Big Bear, is still very low in the early evening northern sky. The Little Dipper, otherwise known as Ursa Minor, the Little Bear, is hanging by its handle above the Big Dipper. The North Star is at the end of its handle. Because Polaris shines directly above Earth’s North Pole, it appears that all the stars in the sky revolve around Polaris once every 24 hours, including our sun.

The later you stay up in the evening, the more you’ll see as the best part of the December skies rise in the east. By 8 to 9 pm, you’ll see Orion the Hunter, the wonderful winter constellation, proudly showing off its bright stars. Its calling card is the three bright stars in a row that make Orion’s belt. The bright constellation Taurus the Bull, with the great Pleiades star cluster, precedes Orion. Just north of Orion is the constellation Gemini the Twins, with the bright stars Castor and Pollux that mark the heads of twin half-brothers Castor and Pollux. I call this part of the sky “Orion and his gang.” There’s much to explore with the Sky Guide app in December’s night skies.

Wednesday, December 21st, marks the winter solstice, the longest night of the year in the northern hemisphere and the shortest night in the southern hemisphere. On December 21st, the sun shines directly overhead at noon over the tropic of Capricorn, south of the Earth’s equator. From now until late next June in the northern hemisphere, the sun will gradually climb northward, getting higher and higher in the sky.

Have a fun-filled and star-filled most holiday season!

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul, and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications. Available at bookstores and online at

If you have any astronomical questions or want me to write about something you’re seeing in the night sky drop me a line at