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Sun, 10 Dec 2017 - A very favourable year for the Geminids

Weather permitting, 2017 should be a great year for observing the Geminids, with peak activity due to occur durig the night of Dec 13-14 (Wed-Thurs). Geminid rates will also be quite high during the night of Dec 12-13 and also fairly good during the nights of Dec 11-12 and Dec 14-15, but do be aware that rates drop off quite steeply in the nights after maximum.

Geminid meteors can be seen at any time of the night, with the numbers seen increasing as the evening progresses and peaking at around 2am local time.

The Geminid meteor shower is so named because the paths of the meteors it produces, when traced backwards, will appear to radiate from a position in Gemini, close to the bright star Castor.

A good fraction of Geminid meteors are bright. 

With their parent object, 3200 Phaethon, being an asteroid rather than a comet, the particles that produce the Geminid meteors tend to be more robust and thus Geminid meteors, though still brief, tend to last slightly longer than those from other meteor showers ... giving observers a better view. This difference does however also result in very few Geminids leaving persistent trains.  Many observers also note brighter Geminids to be yellow-green in colour.

The Geminids will be particularly favourable in 2017 because:

- On the night of maximum, Dec 13-14 (Wed-Thurs), the Moon will be a thin crescent, rising very late in the night and so will not hinder observations.

- Moonlight will only be a minor convenience when observing the rise in rates during the nights leading up to maximum (Last Quarter is on Dec 10).

- Peak Geminid activity is predicted to occur during the UK hours of darkness.

There are some key points to remember, however:

- December nights with clear skies can be very cold, so remember to wrap up well.  Lying in the snow is to be avoided!

- The number of meteors seen is rather sensitive to the darkness of the sky background, so aim to observe from a location that is as dark as possible, has a clear view of the sky and is somewhere where you won't be disturbed and won't disturb others.

- Don't look directly at Gemini.  Any Geminid meteors that appear there will be approaching you almost head-on and so will have very short paths against the sky background.  You will see more Geminids if you observe an area of sky around 30 degrees away from the Geminid radiant.  This should also be around 50 degrees above the horizon. The area involved will obviously need to change as the night progresses - the Perseus-Taurus area may work well in the mid to late evening, whereas the "fore-paws" of Ursa Major will be better in the early hours of the morning.

- Although many sources may quote a peak activity time of around 06h UT on Dec 14th, the Geminid peak is not particularly sharp and rates will be at similar levels for several hours.  Indeed, it appears to be the case that the activity level of fainter Geminid meteors occurs several hours before the peak time for brighter Geminids.  In practice, the most significant factor tends to be the altitude of the Geminid radiant above the horizon ... which peaks at around 2am local time.

- Ignore the "wild" numbers in sensationalised news stories that promise "(up to) 120 meteors per hour" or "two meteors every minute".  (Such reports tend to fall into two categories.  One is "clickbait", with a sensational headline being used to draw you to the website and thus allow it to extract more income from advertisers. The other is usually due to people quoting numbers, such as the ZHR value, without actually understanding what they represent) .  Also expect to be disappointed by news stories, some from normally reputable organisations, that illustrate meteor showers using images of (curved) star trails!

- Although the peak ZHR for the Geminids can reach 120, the ZHR corresponds to an observed meteor rate that would only be seen under clear transparent skies, free from any light pollution ... and with the Geminid radiant directly overhead. These conditions will not be met at any time of the night from the UK.  From a reasonably dark location, the number of Geminids you see per hour will probably be down in single figures at the start of the night, but should be well into double figures by the late evening, and possibly exceeding 30 per hour by the time that the radiant is highest around 2am.

Good luck!   Do let us know what you see.  You can email your reports to:

Although you can, of course, just sit back any enjoy the show, it is always a good idea to keep a record of the meteors that you see.

The SPA website includes useful guides to  Imaging Meteors and to  observing meteors visually


Added by: Tracie Heywood