Comet 46P/Wirtanen (aka the “Christmas Comet”)

2018-12-17 04:44:14.000 – Ryan Knapp, Weather Observer/Staff Meteorologist


Working the night shift over the past 13 years, I am always in awe of the night sky. While my background is in meteorology (the study of weather) and the Observatory is purely a weather-based observatory, it is difficult to step out on a nightly basis and when we are clear, not have at least an inkling to know what I’m looking at beyond the lowest layer of earth’s atmosphere. There are the obvious constants (moon, stars, constellations, etc) but I am always on the lookout on space related blogs and websites for other interesting events. These types of events would be the International Space Station, meteor showers, numerous planets in the sky at once and/or their alignments, comets, or lunar eclipses just to name a few. For December, there were/are a few close encounters of the moon and various planets (not literally, just perspectively), there were/are two meteor showers (Geminids and Ursids), and the passage of Comet 46P/Wirtanen (aka the “Christmas Comet”).

This shift had three things I was looking forward to viewing – the close approach of the Moon & Mars, the peak of the Geminids and Comet 46P at its brightest. However, this is Mt Washington, so the weather would be the determining factor on how many of these events I would actually get to see. Summit fog obscured the Moon & Mars approach. Summit fog obscured the peak of the Geminids. And overcast skies obscured the viewing of Comet 46P. Am I surprised? Nope, Mt Washington spends over 60% of the year in the clouds and the times that we are clear, partly to mostly cloudy conditions are statistically favored. So I knew statistically speaking, my chances would be low. However, with the exception of the Moon/Mars date, since meteor showers and comet passages occur over multiple nights, I was still able to see both at times on the nights we were generally clear.
While I was doing my observations on the night of the 12/13th, I saw numerous shooting stars but was unable to see the comet, as I couldn’t place where it was until it was too late and it had been obscured by the western horizon. Knowing we would be in/under clouds on the night of the 16th and likely beyond, my last good chance would be on the 15th. At first we had mostly to partly cloudy skies, so I wasn’t holding out much hope but then the ridge built in and the skies cleared out and opened up. Even better were winds were dampened to the 15 to 30 mph range making it possible to weight down a tripod for long exposures. So I split my night shift break in two taking 30 minutes to snap a few images with the moon still out and then another 30 minutes later in the night after the moon set. The times between I still had to take weather observations so each time I stepped outside it was like a giant game of “Where’s Waldo?” as I scanned the sky to see where the comet had moved in relation to my position on Earth. All in all a fun night of weather observations for work and night sky viewing for fun.
Looking up at Comet 46P Saturday nightLooking up at Comet 46P Saturday night
Summit sign, Obs Tower, Milky Way and Comet 45P (left side halfway down)Summit sign, Obs Tower, Milky Way and Comet 45P (left side halfway down)

So what is the next thing I am looking forward to in the night sky? Hands down that would be the total lunar eclipse on 20/21 January 2019, which will be visible across the entire western hemisphere (if the skies are clear for your location). I was on the summit for the 28 September 2015 total lunar eclipse and we were fortunate enough to be clear to view it (and being me, photographing it). I am hoping to be fortunate enough to view it this upcoming go around as well. But it is too hard to determine that as of now as weather models that far out are rubbish. So for now, fingers crossed it all works out!

Lunar Eclipse from Mt Washington 28 September 2015Lunar Eclipse from Mt Washington from 28 September 2015


Ryan Knapp, Weather Observer/Staff Meteorologist

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