More often than not you will find the image is underexposed and very noisy as a result. (This ranks as one of my most regretted mistake in 40 years of photography and one that I hope will never repeat.) It is far better to check your exposure using the histogram function on your camera. (Check the instruction book if you are not already familiar with that feature.)
My start point for exposure is 15 seconds and I choose the iso. setting based upon the maximum aperture of the lens. For example: If the lens will only open up to f4 I would set the camera to 800 iso. F2.8 would give me 400 iso. and f2 would allow me to set 200 iso. As you can see, the faster the lens on your camera the lower the iso. and therefore the lower the digital noise you will record. Likewise a slower lens like F5.6 would need a setting of 1600 iso. with all the extra noise that entails. Because the Aurora tends to move and shift about, a longer exposure tends to just result in a less defined amorphous result. The other problem with longer exposures is that the Earth’s rotation will cause the stars to streak rather than be recorded as points. 15 seconds seemed to be the optimum in the tests I made. (The two larger spots near the bottom of the photograph above are planets by the way.)
I find the best shots also have some foreground interest such as trees or even buildings too but if you include illumination in the foreground this will have to be balanced with the main exposure as well. Sometimes you can be lucky with this but other times you may need to take two different exposures and combine them in the computer when you get home.
If that lot made sense then you probably know what you are doing with a camera already and can skip the next bit but it is the most common error made when taking pictures in snow conditions so I had better mention it.
If you are taking pictures in snow on an automatic exposure mode, your pictures may come out too dark. This is simply because the camera does not understand what it is being pointed at. It’s cleverly made but not actually able to think for itself.
A camera’s exposure meter is designed to take an average picture of an average subject under average lighting. If it is pointed at a bright subject it will react as if it is pointed at an average subject that is being too brightly lit and it will reduce the exposure to compensate. End result your picture looks too dark. Snow of course is a bright subject.
Some cameras have a special “Snow” setting which might compensate for this problem but you do need to turn it on. If that is not an option you need to find out where the exposure compensation settings are. They are usually fairly easy to find but all cameras vary.
What you need to do is give it some overexposure or positive compensation. Not much, probably one stop or less and that will brighten things up a little. If you apply too much your highlights could burn out so you don’t want that because you cannot repair them later. Check your shots as you go. That histogram feature we mentioned earlier is good for that. Some cameras make over exposed parts of you image blink on and off on the screen in playback as a warning. That might be a feature you need to turn on.
I guess what I am saying is that if you want to get decent pictures you might actually have to read the instruction book again. It should all be in there.