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I've got a Celestron Astromaster 114 telescope. I live in Los Angeles and would like to get a look at 46P/Wirtanen. Can anyone tell me when this comet is going to brightest and how best to locate it in the sky? It's my (perhaps incorrect) understanding that it is not especially bright. Any tips/hints/information would be much appreciated.

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If you have, or can borrow binoculars, that is probably a much better way to try to find the comet than your telescope. If it's set up like the one in the image in your question (that I've added) you don't have a computer read-out for RA/Dec or any way to position your mount accurately so that the polar axis points at polaris. The bright skies in LA will make doing so manually a bit of a challenge, and lack of previous experience doing so will make it even more of one.

Go to in-the-sky.org and then to Planetarium view. Go to the bottom right and type 46P into the Find box and it will find your object's name and then display it for you. Turn on the Alt/Az grid instead of the RA/Dec grid and you can see that 46P is about 60 degrees up at 8 PM your time. Lay on your back and take some time to look around with your binoculars.

It should set your location to Los Angeles automatically, but double check that.

You can see that there are some very bright stars lined up to make your viewing easier. First is Betelgeuse the bright corner star in Orion (do not say Betelgeuse three times in a row!) then Aldebaran the eye of the bull, then the comet.

At about 4th magnitude you should be able to see it as a green fuzzy star, unlike anything else. You can also zoom in using in-the-sky.org to see the local stars. The comet is going to be moving relative to the stars, so don't make zoomed-in print-outs and try to use them six hours or a day later.

Set up anything you have around the spot where you'll be laying down, to block lights from neighbors or the street, turn your own lights off. You are going to be looking East-Southeast about 2/3 of the way up to the zenith in the evening, and 46P will remain high in the sky most of the night.

Have fun!

Oh, the telescope! Once you've gotten good at finding 46P with binoculars and have some feel for the other stars nearby, then try the absolute lowest magnification you have on your telescope and just look around slowly. Loosen up your mount so you can move the tube by hand, and scan around until you see the blue fuzzy blob again.

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Peak magnitude is "now", or a few days either side of the 17th of December. The peak magnitude is about 4.0 (so this is not like Hale-Bopp), (assuming nothing unexpected happens) it can be found passing the Pleiades over the next few days. The waxing moon will affect the evenings, which you should consider when planning observations.

In-the-sky have an ephemeris for the comet:

Space.com have a finder chart and general discussion

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  • $\begingroup$ That ephemeris data looks very precise, but is greek to me. I did manage to find a video which has a lot of good general info but is hardly precise about locating the comet. There's a marginally more helpful star chart from the university of maryland. $\endgroup$ – S. Imp Dec 15 '18 at 23:00
  • $\begingroup$ Well now would be a great time to learn what it all means. Start by researching what "right ascension and declination" mean. $\endgroup$ – James K Dec 15 '18 at 23:21
  • $\begingroup$ I seriously doubt I'll be able to calibrate my telescope mount's placement with sufficient accuracy to find this object with those ascension and declination values. $\endgroup$ – S. Imp Dec 15 '18 at 23:40

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