Astro Bob: How to see Comet Leonard at its best

The year's brightest comet is now on display in the pre-dawn sky this week and next. Here's how to find it.

Leonard Dec1 Mobberley.jpg
Comet Leonard, discovered last January, is now bright enough to see in a pair of binoculars from a dark sky before dawn. Contributed / Martin Mobberley
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Compared to the splendid appearance of Comet NEOWISE last July, Comet Leonard (C/2021 A1) won't come close, but it may very well become the brightest comet of 2021. By bright, picture a faint blob visible with the naked eye from a dark sky. But with a pair of binoculars or small telescope, this seasonal, celestial gift should prove an attractive and delicate sight for observers with access to the outer suburbs and countryside.

Comet Leonard orbit.jpg
Comet Leonard's orbit takes it out to the Oort Cloud, a roughly spherical repository of billions of comets that orbit the sun at vast distances. Leonard has traveled about 3,500 times the Earth-sun distance for a brief spin around the inner solar system before returning to its frozen fastness. Its position is shown for Dec. 12, when it comes closest to the Earth. Contributed / NASA, Horizons

Senior research specialist Greg Leonard at the Mt. Lemmon Observatory near Tucson, Arizona discovered the comet on Jan. 3, 2021, when it was nothing more than a faint, distant speck. Since then, it's inched steadily closer to both the sun and Earth and will reach perihelion — closest approach to the sun — on Jan. 3. Two weeks prior on Dec. 12, the comet will pass nearest Earth at a distance of 21.7 million miles (34.9 million km).

What will we see? Comets are always a little tricky to predict because they have a penchant for unpredictability. Being fragile, they're liable to break apart when nearing the sun. Solar heating vaporizes a comet's ices, creating pressures within and without its fragile body that can sometimes tear it apart. It's even possible that something of the sort is happening right now because Leonard, after steadily brightening, has recently plateaued.


Leonard Map Dec 1 to 10 am.jpg
Use this map to find the comet, which is best visible around 5:30-6:30 a.m. local time in the northeastern sky before the start of morning twilight. The bright star Arcturus, found by following the arc of the Big Dipper's Handle, will help point you to Leonard. Look for a misty or cottony patch of light in binoculars. Careful observation will reveal a short, upward-pointing tail. Contributed / Stellarium with additions by Bob King

On Thursday, Dec. 2, the comet glowed at around magnitude 6.5-7, hovering at the fringes of naked-eye visibility. In a pair of 10x50 binoculars for instance, you should expect to see a soft patch of light about half the moon's apparent diameter with a brighter center and a faint streak of a tail pointing to the upper right.

Because the comet is approaching both the Earth and sun it's really starting to pick up speed. For the next few mornings (through Dec. 7) you'll find it in the constellation Bootes the Herdsman, not far from the brilliant, orange giant Arcturus. Let this star be your guide.

For instance, on Friday morning, Dec. 3, it will appear 11 degrees (about one fist held vertically at arm's length) to the upper left of Arcturus. At the same time, it's just one moon diameter below the bright star cluster M3, which is also visible in binoculars as very small, fuzzy spot. As each day clicks by, the comet should slowly brighten to at least magnitude 5 and possibly brighter. This increase in intensity will help offset its decreasing altitude in the sky.

Comet Leonard Dec 10 to 12 2021.jpg
Comet Leonard really gets moving closer to mid-month, when it rapidly drops into the dawn light. It's still expected to brighten at around magnitude 4.5-5 at best. If this holds, then you should be able to track it through at least the 11th. Contributed / Stellarium with additions by Bob King

No moon mars the darkness, so now through about Dec. 11 will be the best viewing slot for northern hemisphere skywatchers. After Dec. 11, it's briefly close to the sun and very difficult to see, then swings into the evening sky. While the viewing time is more convenient, Comet Leonard moves rapidly south and will only be visible from the far southern U.S. and the southern hemisphere as it slowly fades from view.


Beauty can be brief, and nothing demonstrates this as well as a comet. My last view of Comet Leonard was during the Nov. 19 lunar eclipse. With the moon tucked deeply in shadow at mid-eclipse, I stole a view of the object in a dark sky in my 15-inch telescope. I'm currently in Antarctica with hopes of viewing the December 4th total solar eclipse from near Laurie Island in the South Orkney Islands. From my present location, the comet is buried deeply below the northern horizon. Funny thing. When I return home it will be lost in the solar glare at dusk.

Win a few, lose a few. All the more reason I hope you get to see the comet. Take advantage of the next clear morning. Find a dark place and give your eyes a few minutes to adapt. Then raise your binoculars and seek the feathered creature just arriving in the neighborhood after a 35,000-year pilgrimage from the outer solar system. Say "hi" for me!

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at .

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at
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