Tripod
To photograph at night you will need a tripod to minimize camera shaking. Handheld aurora photos will not be sharp. To adjust settings comfortably, the tripod should be nearly your height.

Camera
Your camera needs to have the option of manual focus and a complete manual mode which allows you to adjust aperture, exposure time and ISO separately. Best cameras are dSLRs (although new mirrorless cameras are good as well). here you can put on a good lens for the night and will get the best quality.

Lens
You should use a fast lens (meaning wide aperture, with a small f-number like f/2.8 or better) to make the most of the available light. Lenses with f/4.0 are doing fine also but you will have to crank up the ISO. Auroras often stretch all over the horizon. To capture a big part of it, you want to have a wide-angle lens (24mm or wider).

Remote control
To further minimize camera shaking, use a remote control for taking pictures without touching the camera. Many cameras have a delayed shutter mode (1sec..20sec) which is a good alternative.

Spare batteries
In cold weather your batteries will discharge quite fast, so it is important to have at least one extra battery with you. Using hand warmers, you can revive the batteries to get the last bit of energy out of them (tip from Jake D., thanks buddy).

Sun hood
At times you will be in damp weather or it will be windy. Moisture can be a problem especially in low temperatures. Your lens will get icy. One way to delay that problem is putting the sun hood onto the lens.

Photographing auroras is all about finding the combination of aperture, ISO and exposure time which works for you. All three are dependable on each other and in the end it is up to you to experiment and come up with the best result. There is no fixed recipe.
Short exposure times let you ‘freeze’ details of the aurora, long exposures blur out the details. The wider/faster your lense is (a small f-number) the more light gets into the camera. This will allow for shorter exposure times. High ISO settings cause often noise in the photo but allow also for shorter exposure times.
Lets say the following settings result in a good image: aperture f4, ISO 800 and exposure time 5 sec. Now you want to freeze more of the aurora details, so you need to shorten the exposure time to – lets say – 2,5s. Your photos will be much darker now but there are two solutions to fix that. ISO to 1600 or f to 2,8.
Best thing to do is to go out in darkness and play with your camera settings.

If you are in a dark place to watch auroras the auto-focus of your camera will not work. There is simply too little light available. To achieve focus there are several options:
– turn off the auto-focus, switch your camera to live view and use the manual focus ring. Once in live view zoom into the frame until there is – for example – a star or the moon. Then turn the manual focus ring until you find that star at its sharpest.
– if the star/moon approach does not work, point a strong flashlight to a tree or rock and use the same live view technique.
– point a strong flashlight to an object (tree, rock, etc) which is relatively far away. Then focus using the auto-focus. After that switch the auto-focus immediately off. This is a good alternative if your camera does not have live view.
– focus during daylight to a far-away object and switch off the auto-focus. Use tape to fix the manual focus ring. This might work well, but be sure to test it out.
Remember to always check the photos you captured if they are as sharp as you want to. If not, adjust again

White balance is a matter of taste mostly. Some prefer photos in a certain look (warm or cold). This can be achieved with the white balance. Unless you shoot in RAW and post-process on your desktop or laptop, you want to get the right white balance for you when you are out shooting. Your camera probably has different presets (sun, shadow, etc). Try them out and choose what looks best to you. If you have the option K (temperature Kelvin), use it. Aurora photos come out the best somewhere between 3000…4800K.

As mentioned in part three of this series, the Moon phases will affect your aurora experience. This is also true for the photos. To get the best mix of landscape and auroras a quarter to half of the moon should be visible. This will give enough light to capture the landscape and still be dark enough to preserve a lot of details and colors of auroras. Both, Full Moon and New Moon have their own advantages: Full Moon = great light in landscape, less details and colors of auroras. New Moon = poor light in the landscape, best details in the starry sky.

Our Earth rotates constantly and the position of the stars in the sky changes as well. If the camera exposes too long the stars will look like short lines in the photo instead of points. That is called star trails. Sometimes it is wanted and sometimes not. To avoid star trails all you have to do is follow the ‘500 rule’:
Find out the focal length of your lens, for example it can be 16mm. Now divide the number 500 by the focal length you found. Lets round the result 31 to 30. This means you can have a maximum exposure of 30 seconds. Any longer and star trails will be visible.
There one last important thing for this rule. As such, this rule only for full frame cameras. Cropped cameras (DX, APS-C, Micro four thirds, etc)  have a so-called crop factor or focal length multiplier. If you are not sure, you can find the specifications for most cameras here. Lets say a camera has a crop factor of 1,5 and a 16mm lens. Now the calculation is 500 / (16mm x 1,5 crop factor ) -> 500/24 = 20 seconds.
The movement of stars can also be used for creative photography: