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Tuesday, December 08, 2020


Geminid Meteor Shower 13-15 December 2020

The northern horizon at 4:00 am ACDST as seen from Adelaide on Monday December 14. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).The northern horizon at 3:00 am AEST as seen from Brisbane on Monday December 14. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).

The Geminids are unusual meteor shower in that their parent body is 3200 Phaethon, an asteroid, rather than a comet. It is speculated though that Phaeton is actually a "gassed out" comet, and so the debris that makes up the Geminids may still be cometary particles, but is more likely broken rock fragments from its close approach to the sun.

The Geminids are usually a fairly reliable meteor shower and with the Moon almost new rates should be  excellent.

The Geminids have a broad peak and will show good activity well before and after the peak on the day before and after. The peak is December 14, 00h50m UT. That is 11:50 am AEDST December 14 in Australia.  Despite the peak being during daylight hours, the best viewing will be from around 2-3 am AEDST (1-2 am AEST) on the morning of the 14th in Australia. As the radiant doesn't rise until just before midnight (daylight saving time) in most of Australia, so you will still have to disturb your sleep for this one.

Northern Australians should see a meteor every 1 to 2  minutes under dark skies in the early morning of the 15th between 1:00 am and 4:00 am local daylight saving time. Obviously under suburban skies you will see fewer.

It is best if you can find some  object to obscure the Moon so your night vision is not too compromised by the brightness.

You can find predictions for your local site at the meteor flux estimator (choose 4 Geminids and date 13-14 December, don't forget to change the date to 2020). You will have to enter your local latitude and longitude for your site. I have also made a table for major cities below.

Unfortunately, both Chrome and Firefox have changed their security settings to prevent plugins from running, and the flux estimator only runs under Internet Explorer now.
You can follow the progress of the shower at the IMO Geminids Live page.

At 1.00 am in the morning AEDST (midnight, AEST) Castor (alpha Geminorum) is about two hand-spans above the horizon and 10 hand-spans to the right of due north. Pollux, the other twin, is less than a hand-span to the right again. The radiant is just below Pollux.

When you get up, allow at least 5 minutes for your eyes to adjust and become dark adapted (even if you have stumbled out of bed in the dark, here's some hints on dark adaption of your eyes so you can see meteors better). 
Be patient, it may be several minutes before you are rewarded with you first meteor, then a couple will come along in quick succession (a meteor every 1 to 2 minutes is an average, they won't turn up like a ticking clock but more or less randomly).

Predicted meteor rates for selected towns

TownMorning December 13 Morning December 14Morning December 15
Adelaide11 meteors/hr28 meteors/hr11 meteors/hr
Brisbane14 meteors/hr35 meteors/hr16 meteors/hr
Darwin20 meteors/hr53 meteors/hr19 meteors/hr
Perth13 meteors/hr34 meteors/hr11 meteors/hr
Melbourne9 meteors/hr24 meteors/hr9 meteors/hr
Hobart7 meteors/hr18 meteors/hr7 meteors/hr
Sydney11 meteors/hr28 meteors/hr12 meteors/hr

Choose a viewing spot where you can see a large swathe of sky without trees or buildings getting in the way, or with street lights getting in your eyes. The darker the spot the better (but do be sensible, don't choose a spot in an insalubrious park for example). 
While the radiant is where the meteors appear to originate from, most of the meteors will be seen away from the radiant, so don't fixate on the radiant, but keep your eye on a broad swath of sky roughly centered just above the radiant (as the radiant doesn't rise very high, looking exactly at the radiant will mean you miss some higher up).

A lawn chair or something similar will make your observing comfortable (or a picnic rug spread on the ground and a nice pillow), and having a Thermos of hot coffee, tea or chocolate to swig while watching will increase your comfort. Despite it being summer, make sure you have a jumper or something as the night can still get cold.

Guides to taking meteor photos are here and here.

As well, Orion and the Hyades will be visible. So it will be a quite nice morning for sky watching. Keep an eye out for satellites! There may be a bright ISS pass on the morning of the 14th from your location.

Cloud cover predictions can be found at SkippySky.  

Here is the near-real time satellite view of the clouds (day and night) http://satview.bom.gov.au/


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