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The headlines drool with excitement: “Are you ready for the big comet show?” “Comet Leonard Brightening More Than Expected!” “Don’t Miss 2021’s Best Comet.” So, is it really worth a look? Here’s Bob Berman’s take and a few key viewing tips.
One big problem: very few will see any trace of this comet. To be sure, there is indeed some good news. The comet’s location is easy to find; this week, it will pass unusually close to super-dazzling Venus.
Where Will Comet Leonard Be Visible?
Comet C/2021 A1 (Leonard) will pass below Venus on Friday evening, December 17, and Saturday, December 18.
And will be far left of Venus from Sunday the 19th right through Christmas.
Also, it’s magnitude 5, technically matching the faintest star of the Little Dipper, which is visible to the naked eye.
But it’s oh-so-low, meaning its dim light must bulldoze its way through thick horizon air, and not be blocked by any distant hills or buildings. Moreover, a 5th magnitude star is one thing; a 5th magnitude comet is quite another, since that same brightness is spread out over a wide area, making it much harder to detect. But binoculars should do the job.
Perhaps the biggest issue is that you need inky-black conditions. Unpolluted skies untouched by city lights. Small towns are too bright. Suburbs are too bright. You’ve got to be in the boonies or a nice desert location like Arizona’s Organ Pipe National Monument. And how many will get to such a place?
When to See Comet Leonard
But if you have binoculars, sweep them below or left of Venus this weekend. Look as soon as full darkness falls, around 5:30 PM., toward the west, low on the horizon.
Venus and Comet Leonard will be higher up at, say, 5:10 PM, but twilight will still be glowing, which is a no-no. But don’t wait too long past 5:30 because the comet gets way too low and then sets. So it’s a real challenge to hit the right time.
This observer, meaning myself, has been watching comets for more than a half century, and lives in dark mountains, and even has an observatory, and I’m not too excited. That’s because those gorgeous photos you’ve seen showing a lovely green nucleus and coma, along with a distinct tail, are not what your binoculars will reveal if you see it in person. Viewed in real time, live, your binoculars will probably show it as a mere blurry blob with no tail and no color.
Comet Leonard. Credit: Adam Block at UArizona’s Mount Lemmon Sky Center.
2021’s Best and Brightest Comet?
Some news sources tout Comet Leonard as 2021’s best and brightest comet. Frankly, comets are difficult to predict in terms of brightness and visibility. Comet Leonard is visible to the unaided eye—but just barely. Again, with comets, you really never know.
It’s much fainter than last year’s Comet Neowise, so that will give you a big clue what to expect, whether you saw Neowise or whether you failed to find it.
But hey, it’ll be fun to try, a triumph if you succeed, and in any case you’ll be staring at Venus at its best. In fact, do also point those binoculars at that dazzling planet and, if they’re steadily braced or image stabilized, you’ll see its current moonlike crescent shape. It’s win-win. Sort of.