December brings cold winter nights and some of the clearest skies of the year for many locations. Bundle up to keep warm and get outside for some holiday stargazing fun!
The Great Conjunction
Are you ready for the Great Conjunction on December 21st? This rare astronomical event refers to when the planets Jupiter and Saturn appear close to each other in the sky. This event occurs in an approximately 19 year cycle. This approach will be very close, at a separation of only 6 arcseconds between the planets! The last time these planets appeared this close was in 1623, and the next time will be in 2080. Make sure to take the one-in-a-lifetime chance to observe Saturn and Jupiter simultaneously! The planets will be low on the south-western horizon as the sun sets, so get your cameras and Barlow lenses ready for this rare observing opportunity!
Thanks to the New Moon of December 14th, skies will be dark enough for nice views of distant deep-sky objects with a telescope. Check out open cluster M45 (Pleiades), the Andromeda Galaxy (M31), and the many gems within our namesake constellation Orion, including M42 the Orion Nebula, emission nebula M78, and the large emission patch NGC 2174/2175 also known as the Monkey Head nebula. If you have a 10" or larger aperture telescope with a Hydrogen-beta filter, take advantage of the New Moon to go after views of the elusive Horsehead Nebula located near Alnitak - the easternmost star of Orion's easily recognizable belt. New Moon also coincides with a total solar eclipse, visible from Chile and Argentina, and partially visible from a large portion of South America.
One of the most famous meteor showers, the Geminids, will be most active on December 14th. This impressive shower is known to produce up to 120 multicolored meteors per hour at its peak. This year, the new moon should cause little interference with viewing meteors. While this shower can produce meteors nightly from December 4th through the 17th, the best chance to see a high concentration of meteors will be on the night of December 14th.
Best Binocular Targets
While 50mm binoculars are good for December stargazing, bigger 70mm, 80mm, or larger binos will reveal brighter and better views of celestial gems, of which there are plenty to enjoy in December skies. The glorious open star cluster M45, also known as the Pleiades, will be nearly overhead in the constellation Perseus. A little more north and overhead you'll find the Andromeda Galaxy (M31), which really shines in big binoculars. Slightly to the northwest of M31 you'll see the beautiful Double Cluster of Perseus.
Best Telescope Targets
All of the binocular targets listed above also make great telescope quarry, but December skies offer great opportunities to see objects that require a telescope too. First, slew your scope just a few degrees southwest of M31 to find M33, a distant face-on spiral galaxy that's about 2.5 million light years (MLY) away from Earth. In the constellation Sculptor far to the south, try to find NGC 253, the impressive "silver dollar" galaxy. There's a swarm of other galaxies to see in the general area of NGC 253 - all part of the "Sculptor Group" of galaxies. Use a star chart or the Orion StarSeek app and hunt them down! In Pisces, look for M74, another face-on spiral galaxy like M33, but one that is almost 30 MLY farther away from us. Finally, check out NGC 1300, a classic barred spiral galaxy that is approximately 61 MLY away from Earth with a monster black-hole in its nucleus.
With a 10" or larger telescope from a dark sky site, try to track down the picturesque Horsehead Nebula near the eastern star of Orion's belt, which is named Alnitak. Using an Orion H-Beta Nebula Filter will improve your chances of seeing this faint absorption nebula.
All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars.