The Geminids is often the best meteor shower of the year, often with 120 multicoloured shooting stars an hour. This year, a nearly full moon will rise before the meteor shower starts, however, you should be able to still see 20 of the brighter shooting stars an hour. Worth staying up late on Saturday the 14th or getting up early on Sunday the 15th to view this at its peak.
Image of a Geminids courtesy of Bryce Bradford @ flickr
The Geminids is special among meteor showers because it is caused by the debris left behind by an asteroid, while most meteor showers come from the dust tails of comets. The asteroid in question is 3200 Phaethon, which is an unusual asteroid because it orbits the sun like a comet in a steep elliptical orbit. Some people refer to it as a rock comet, which would be a great name for a '70s cover band, but basically means it is a comet made of rock instead of ice.
Image of the path of 3200 Phaethon courtesy of Tomruen @ Wikimedia Commons
Shootings start are at the most grains of sand, though usually, they are nothing more than specs of dust. They are floating out in space when the Earth runs into them. The speed that they enter the Earth's atmosphere means that they burn brightly, with dust creating regular shooting stars and sand-sized meteors creating fireballs bright enough to see even in the suburbs.
The Geminids are known to be colourful and the colour comes from the different elements that make up the shooting stars. Iron makes yellow shooting stars, silicon burns red and green is the result of copper.
The unusual nature of the Geminids means that, unlike other meteor showers which tend to be best viewed from midnight to dawn, the Geminids starts earlier. So the best viewing time will be from 10 pm and will continue until the predawn light. Unfortunately, the full moon will have already risen when the meteor shower starts.
Normally the plan to watch a meteor shower is to get as far away from light pollution as possible. The moon will be the biggest challenge for this years Geminids, but it is still important to go somewhere dark. This could be a bushland area, a quiet beach or, if you are very keen, hike up a mountain to watch them from the top.
To spot shooting stars you want to find a nice place to sit or lie with the view of the sky. Let your eyes adjust to the dark and avoid any light sources. So turn off flashlights, leave your phone in your pocket and hide your smartwatch. Even a campfire can affect your night vision and it takes up to 20 minutes to recover your night vision.
Basically, you look at the sky until you see a shooting star. Many people will try to find the radiant point, which is where the shooting stars appear to come from. In the case of the Geminids, it is the constellation Gemini, but the shooting stars can appear anywhere in the sky. This year it is better to ignore the radiant point and look wherever the moon isn't.
Image the constellation Gemini courtesy of Till Credner @ Wikimedia
Viewing details around Australia
The main period of the Geminids run from December 7 to 17 with the peak falling on the evening of Saturday 14 and Sunday 15 in Australia. I was going to skip writing about the Geminids this year, because of the moon, but after doing a little research I have learned that astronomers still expect the brighter shooting stars to be visible through the moonlight. So you should catch around 20 shooting stars an hour, while in most years you get 120 an hour.
In Sydney and Melbourne , viewing on the night of the 14th starts at around 11 pm. Moonrise will unfortunately be about an hour before that. In Brisbane, the Geminds can be viewed from about 10 pm in the sky to the North East, with the moon rising at 8:35 pm. In Adelaide , you need to wait until nearly midnight for viewing the meteor shower and moonrise is about 10:24 pm. Over in Perth, you can watch the meteor shower from 10 pm until dawn, with moonrise being at 9:24 pm.
Photographing shooting stars
If you have a good camera it is worth trying a little bit of night sky photography, with shooting stars being the ultimate challenge. Shooting stars are faint and move quickly, so along with a good camera, a fast lens, and a tripod, to successfully capture a shooting star, you will need a great deal of luck.
Photograph courtesy of Amir shahcheraghian @ Wikimedia
Obviously, you should use a decent camera such as a DSLR or mirrorless camera. More importantly, you need a fast lens. Most people buy a camera and lens kit to start with, and while their zoom lens may be very good it is likely to have an f-stop of f/3.5 or f/4. This may still work, but ideally, you will want a smaller, and therefore faster, f-stop number. For this, you often need a prime (non-zoom) lens and these can have f-stops of f/2.5, f/2 or even faster.
The basic process is to set up your camera on a tripod and point it at the night sky. A lot of the time people will try to get some of the landscape in as well to create a cool looking photo. Instead of waiting for a shooting star and pressing the button, which is impossible because the shooting stars are moving too fast, you want to set your camera to continually take photos. With any luck, you will capture a shooting star on one or more images.
Getting the exposure timing right is important. This does change based on your camera and your lens. Normally it will be between 10 to 25 seconds. Longer exposures capture more of the star field and have a greater chance of capturing a shooting star as well. But if the exposure is too long you will just see the background stars and not really see the shooting star.
Image courtesy of Jason Jenkins @ Flickr
The moon will reduce one of the best meteor showers of the year to just 20 shooting stars an hour. It is still worth heading out to somewhere dark on that weekend to see if you can't see a few. Given that it is school holidays, the meteor shower starts earlier, and many people will be out camping anyway, it could be worth viewing despite the lunar light.