Comet 45P/Honda-Mrkos-Pajdusakova only just returned to the morning sky and already it’s on a collision course with the moon. Not literally. Only that the moon is waxing toward full this week and will soon enter the morning sky. When it does, all its glorious light will render what would otherwise be a binocular comet invisible. We first visited with comet 45P/H-M-P in late December and the first half of January, when it huddled in Capricornus low in the southwestern sky during evening twilight. Back then, as it drew nearer the sun, the comet was a bright, compact ball of aqua haze with a long skinny tail, resembling an onion yanked from your garden.
45P swung closest to the sun on last day of last year and is now on a slingshot course for Earth as it heads back out into the cold depths of Jovian space. On Feb. 11, the fuzzy fellow will zoom past Earth at a distance of just 7.7 million miles traveling at 51,000 mph. That’s about 32 times the Earth-moon distance and close as these things go. No worries though — it poses no threat to our planet.
Since rounding the sun, the comet has (for now) lost its tail and become much more diffuse, the astronomical term for ‘fuzzy.’ I got up this morning and took on biting winds and a 7° temperatures to bring you this good news: 45P/H-M-P is visible in ordinary 50mm binoculars! I used 10 x 50s but 7 x 50s and anything larger will work.
Now for the caveats. First, you have to be outside just before the start of morning twilight or about 2 hours before sunrise. Second, you need a reasonably good view of the eastern sky. Not all the down to the horizon but at least low enough to spot the bright star, Altair, in the Summer Triangle. Third, a dark sky in that direction. If city light pollution lights up your eastern sky, you won’t see this comet.
Through my 10 x 50s, I saw a soft, faint hazy patch of light about two-thirds the size of the full moon or ⅓° across. It’s wasn’t obvious at first, but after I played my eyes around the field of view I noticed the hazy spot. Once seen, you can’t miss it. 45P/H-M-P’s current brightness is right around magnitude +8. And slowly fading. If no moon invaded the sky, we’d be able to see the comet in binoculars for at least a week, but once the moon shows, it will make finding 45P nearly impossible for most skywatchers. Being so diffuse, even telescopic observers will have a tough time of it for a while. Through my 10-inch scope this morning, it was a big, hazy blob with a very faint, star-like spot at center.
But not forever. The comet puts the pedal to the metal as it approaches Earth and moves swiftly westward and higher. At the same time, the moon moves east, so that by Valentine’s Day, we’ll see 45P appear near the brilliant star Arcturus around 10 p.m. in the evening sky before the moon rises. Its predicted brightness then will be magnitude +9 and still quite fuzzy, so most of us will lose sight of it in binoculars. The good news? 45P/H-M-P will remain visible in modest telescopes until late in the month.
I hope the throw of nature’s dice nets you a clear, moonless morning soon! ** UPDATE: for additional maps and comet viewing times, please see my recent article on the Sky & Telescope website.