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Updated December 1st 2018
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(Above) 46P captured on December 1st by Rolando Ligustri from Australia
The long wait is finally over. For months 46P/Wirtanen has strictly been an object for southern hemisphere observers however now the comet has moved north and is currently visible in the evening sky for observers at mid northern latitudes. Trained observers from the southern hemisphere have spotted the comet with the naked eye with magnitude estimates varying from +5.7 to +5.2, furthermore the coma diameter has been visually observed between 50 and 72 minutes of arc, if we take the larger estimate that makes the coma size more than twice the apparent diameter of the full moon. Based on these observations the comet is currently on track to peak at mag +3.0 by mid December when it will make a very close approach to the Earth, by which time the comet will be at peak brightness with an even larger coma, just how large the coma will be is uncertain at this time however 3 to 4 apparent moon diameters (at least) isn't out of the question.
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(Above) 46P finder chart from Sky & Telescope. Also check out the wide field chart from Seiichi Yoshida and the Heavensabove real time chart
During early December 46P resides low in the south and reaches its highest position on the meridian after 22.30 UT when it can be found in a region of sky rather devoid of bright stars and vivid constellations. The comet begins to move north east more rapidly each night and from early to mid December it can be found between Eridanus the celestial river and Cetus the celestial Whale. By December 12th the comet will be located not far to the east of naked eye star Menkar or Alpha Ceti which will serve as a good guide post. While you are scanning the area why not check out the famous long period variable star Mira which is currently brightening and now visible with the naked eye with maximum peak expected this January. If you are hunting with a telescope then make sure to check out the spiral galaxy M77 in the nearby, at the time of writing a supernova has exploded within this galaxy at mag +14, however there is a chance it could brighten further and may come within range of modest amateur telescopes and most certainly an easy catch for astrophotographers with smaller instruments.
From December 15th to December 18th Wirtanen will reside within Taurus the celestial Bull and will be very we placed in the evening sky after dark high in the east when it makes its historic close approach. During which time the comet will be visible with the naked eye between two star attractions - the Hyades and beautiful Pleiades (Seven Sisters or Messier 45) open star clusters. The comet will be visible as a large green haze and between the 16th and 17th will pass directly below the Pleiades making for a fantastic visual treat and photogenic prize for astrophotographers. During the peak of the apparition the comet will be visible for much of the night well placed in the sky at a far elongation from the Sun, telescopic observers should be able to detect rapid motion of the comet in relation to background stars as the comet passes the Earth at a velocity of some 50+ km/sec. Keep in mind the moon will be up during this period so the best views will happen later in the night when the moon has set.
By Christmas the comet will have moved into Auriga in the company of bright moonlight but it will still be worth observing as the comet will make a close pass near Capella or Alpha Aurigae, will the comet be visible in such close proximity to a bright naked eye star?, it will be interesting to see. By late December the evening sky will be free of moonlight by which time Wirtanen will begin to fade yet still within naked eye range and a circumpolar object well worth following into the New Year. If you are interested in observing comets using binoculars or telescopes and wish to get more in-depth within the observational side of things when why not purchase my new ebook 'Hunting Celestial Wraiths - An Observing Guide To Comets' (see below), simply email for more.
It's important to say rite now that this comet will not be an object for the public. A person with no astronomical or observational training wont be able to step outside after dark and see a comet in the sky. Wirtanen won't remotely be anything like McNaught or Hale-Bopp, you will not see a great comet hanging in the sky with a blazing tail at all. It's important to address this issue immediately and temper any misguided hype from click bait sources. Remember that even if 46P reaches mag +3 the comet's light will be spread over a large area several times the diameter of the moon, so in reality it will have a very low surface brightness and will look considerably fainter than a star or condensed comet of the same brightness. Furthermore the coma will be diffuse in nature, by this I mean the comet's coma will be very tenuous and gradually fade off into the background sky, in short, it will be difficult to tell where the coma ends and the sky begins, this diffuse quality will be affected greatly by sky conditions and light pollution (LP). In fact, observers from cities or large towns in proximity to LP are not likely to see the comet at all.
46P Wirtanen will be a comet for the amateur astronomer and best scene from dark rural skies far from light pollution, if you re-locate to such a location and allow yourself to acquire proper dark adaption then the comet will be a naked eye object for you. I suspect it will not be dissimilar to 17P/Holmes in 2007 although it will likely be larger in size. The comet will be a treat to observe through binoculars and rich field telescopes and a great way of training your eyes, honing your telescopic skills and fine tuning the art of comet photography for the imagers out there. The most important thing is to enjoy this visitor, we should feel content and delighted that we will have something new to watch in our skies over Christmas and New Year. I wish you all clear skies and happy hunting.
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Welcome to the first ever ebook from Nightskyhunter. This book is aimed at the amateur astronomy enthusiast who is interested in observing comets with the assumption that the reader already has some basic knowledge of the night sky and is competent with observing through binoculars and telescopes. Through 'Hunting Celestial Wraiths - An Observing Guide To Comets' my aim is to cover many of the most important and interesting aspects of the visual comet observing spectrum with the intention of allowing the reader to choose which level of skill he or she may wish to invest within this fascinating field with the information and confidence to take things to the next level and provide valuable cometary observations which could be of scientific value.
The book is complimented with many of my own comet sketches including detailed extracts from my observing logs showcasing many comet observing sessions over the years which is the heart and soul of the book. It is my hope that these sessions will make you feel you are looking through the eyepiece with me. The book is 119 pages with 28463 words and 4.050KB in size and available as a pdf document which costs £5.99. I can accept payments through paypal or direct transfer, simply EMAIL ME if would like to make a purchase, thanks very much. - READ MORE.
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A selection of photo shoots from September to November 2018 covering two visits to the moonlit waterfall at Dunservick along the Antrim coast, an observation of a newly discovered comet from Maghera and a cave with transient waterfall at Ballintoy harbour and moonlit convection. A combination of moonlit and dark night shoots covering still exposures and star trail photography and time lapse shooting. One page report with 22 images and 2 video clips. - REPORT.
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Astronomy is not the only subject I'm interested in. One other such area is severe weather which will be playing a major role on nightskyhunter from now on in conjunction with my other astronomical pursuits. Check out my new N. Ireland Storm Chasing section and view the chase reports and images which detail not only storms but other phenomena such as a moonbows, noctilucent clouds and aurora displays.
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Martin McKenna
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