Observing Comet 46P/Wirtanen

As I mentioned at yesterday’s club meeting, there is a comet moving across the sky this weekend. It is called “46P/Wirtanen” and is currently moving North through the constellation of Taurus, which is just to the right of the constellation of Orion. You should be able to see the comet by looking south around 10pm. The comet is supposed to be visible to the naked eye, but you need to look very carefully. It is larger than the size of the full Moon, and if you see it it will look like a faint, fuzzy blob. Any nearby street lights or thin cloud in the sky will spoil the view, so you will need to find somewhere dark. There are some dark spots along the coast at Longniddry Bents, or up Birsley Brae.

If it’s too faint for your eyes, a pair of binoculars will help (the larger the better). Better still, you could try photographing the comet! A long exposure on the digital camera will bring up more detail than you can see with your eyes. On a photograph you’ll notice the comet is green. There is a photograph of the comet displayed at http://www.spaceweather.com/, where they say:

This comet is an easy target for digital cameras with exposures as short as 10 to 30 seconds. Astrophotographer Juan Carlos Casado offers some advice to novices: “Use Raw file format, a fast lens (at least f/2.8) and ISO settings between 1600 and 3200. The exposure will depend on the focal length. I normally use the 500 rule–that is, exposure = 500 / focal length (mm). It also helps in areas with light pollution to use an antipollution filter. I am now using Optolong L-Pro clip filter which gives excellent color balance.

What the photographer doesn’t say is that you will need to set your camera to manual mode. Manually set the focus on infinity, mount the camera on a tripod, turn off vibration reduction (if your lens has it), set the camera to “M” mode and set the aperture and shutter speed manually. You can use a standard lens, rather than a telephoto, because the comet is quite large. Check out the Christmas tree photo at spaceweather.com.

You can find sky charts of the comet at http://www.cometwatch.co.uk/comet-46p-wirtanen/ and there is a live image of the sky showing where the comet is right now at https://theskylive.com/46p-tracker.

Best of luck!

Steven.

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