Four Evenings to Follow the Moon
See this printable sky map for December 2018 to navigate the skies! This month, we let the Moon guide us through some of the best starry sights in the winter sky.
Just click here or on the image below to open the printable map—then bring outside!
Stargazing in December
For those of us living in the northern hemisphere, December ushers in a challenging season for sky gazing. Our half of the Earth is now tilting away from the Sun, bringing colder temperatures as winter approaches. It can be difficult to generate enthusiasm for spending a cold night under the stars.
On the other hand, the Sun sets early at this time of year, meaning you don’t have to wait long for the sky to become dark. In fact, for most locations in the United States and Europe the earliest sunsets of the year occur in the first 10 days of December. In addition, the cold, dry weather at this time of year typically brings sparkling clear skies, ideal for observing stars and planets.
This suggests that a good strategy is to go outside early on December evenings with a few easy-to find targets in mind. This December, the Moon serves as a handy guidepost to help you find your way around the sky without getting too cold, and you can do it in just four evenings, three days apart.
Four Evenings to Follow the Moon
Our four-night tour begins just after sunset on December 8. Look low in the southwest to find the thin, thin crescent Moon in the constellation Sagittarius the Archer. The paper-thin crescent is a beautiful sight in its own right, but just to the upper left of the Moon lies Saturn, the ringed planet. Saturn is noticeably brighter than any stars in the area. The Moon is right next door at a mere 248,071 miles from Earth, close enough that 12 explorers have walked on its surface. Saturn is more than a BILLION miles distant, and only a few space probes have ever been there.
Three days later on December 11, the Moon has fattened up a bit, now resembling a fingernail. It’s moved into the middle of Capricornus, the Sea-Goat. The stars of Capricornus aren’t very bright, so you’ll have better luck spotting its boat shaped outline if you wait until after 7:30 p.m. when the sky will be darker. Capricornus is one of the oldest constellations, invented by Bronze Age sky gazers more than 4,000 years ago as a mash-up of a fish and a goat.
Take another three days to warm up before venturing out on the evening of December 14. That’s when you find the (almost) first quarter Moon in Aquarius the Water Bearer. Above the Moon lies Mars, the red planet. To the unaided eye, Mars is the palest orange, and when it’s this close to the glare of the Moon, the color of Mars may be difficult to see. Compared to Saturn, the other planet on our map, Mars is a in the Earth’s neighborhood this month, only 111,846,814 miles away.
On December 17, the final stop on our 9-day lunar excursion finds the Moon in Pisces the Fishes, near the part of the constellation known as The Vee. Pisces is a large but dim constellation. Other than The Vee, its most notable feature is a distinctive ring of stars known as the Circlet. Since our last stop three days ago, the Moon’s shape has changed again. It’s now in its gibbous phases, partway between first quarter and full.
Even though December is bound to be cold, the Moon will help you navigate the sky quickly and easily. Stay warm!
December 2018 Sky Map
Click here or on image below to enlarge this map (PDF).
Sky map produced using Chris Marriott’s Skymap Pro
Note: How to Read the Sky Map
Our sky map does not show the entire sky. Instead, the monthly map focuses on a particular region of the sky where something interesting is happening that month. The legend on the map always tells you which direction you should facing, based on midnight viewing. For example, if the map legend says “Looking Southeast,” you should face southeast when using the map.
The map is accurate for any location at a so-called “mid northern” latitude. That includes anywhere in the 48 U.S. states, southern Canada, central and southern Europe, central Asia, and Japan. If you are located substantially north of these areas, objects on our map will appear lower in your sky, and some objects near the horizon will not be visible at all. If you are substantially south of these areas, everything on our map will appear higher in your sky.
The items labeled in green on the sky map are known as asterisms. These are distinctive star patterns that lie within constellations. When getting your bearings under the stars, it’s often easiest to spot an asterism and use it as a guide to finding the parent constellation.
The numbers along the white “Your Horizon” curve at the bottom of the map are compass points, shown on degrees. As you turn your head from side to side, you will be looking in the compass direction indicated by those numbers. The horizon line is curved in order to preserve the geometry of objects in the sky. If we made the horizon line straight, the geometry of objects in the sky would be distorted.