30 second exposure
Motion photography can be broken down into three main categories: Stop, blur, and pan. In general, "stop" photography is catching something in focus that your eye would normally see in motion; you have to use a fast shutter speed, probably more than 1/60 second, to do this. Examples are a kid blowing bubbles, embers flying away from a fire that was just disturbed, a chainsaw spewing sawdust, etc. "Pan" is moving your camera parallel (or in another direction) with the subject so that the focal point is clear but the background is blurry. The typical shot that displays this is someone riding a bike. And "blur" is the opposite of "pan;" the subject is moving in a blur but the background is in clear and motionless. "Pan" requires almost a second of exposure and "blur" usually requires longer exposures. Above, the aurora is an example of blur photography. At 30 seconds of open shutter, the aurora's color is enhanced and it is able to be seen in multiple locations yet the foreground, the trees, are clear.
For aurora and star photography, I read in an article about aurora photography that ISO should be as close to 400 as possible. If the aurora is quite dull, a higher ISO might be needed. It is a good idea to go into the menu of the camera and turn on the long exposure noise reduction feature. An exposure of at least 15 seconds is probably ideal. This means if you do not have a sturdy tripod, it should be set low, you should not move around it, and of course it won't work if it's windy. The shutter release should be depressed not by your finger but by using the timer function. For my camera, for exposures longer than 30 seconds you must use "bulb" which means you can have exposures up to 30 minutes as long as you hold down the shutter release button the entire time. This introduces slight camera shake (from my hand) seen below, but you can tell how much the extra 53 seconds grabs the red light from the nearby city and the neighbor's homes. I need to run to the photography shop and grab a remote to plug into my camera. Another student said the generic brands run as cheap as 20 dollars nowadays. I do not have a wide-angle lens and that is why the strange angles. Although my 50mm lens has a largest aperture of 1.8 thereby letting in more light, my 18mm at its largest aperture of 3.5 can capture a much larger view of the sky so is a compromise. If I wanted to catch just one constellation, I think I would opt for the 50mm because I could get by probably with a shorter exposure and therefore have less noise.
I am supposed to mention an inspiring motion photograph so now I'll mention a family friend Tony Rath (Photography) out of Belize. I grew up next to his parents and he does some amazing things with stop and blur. He recently posted some 90 second exposure photos of the stars on small island we visited a couple of years ago, South Water Caye as well as some stop photographs of dirt bike races and beach volleyball. I can't link to the photos individually, but here is one of his websites.
83 second exposure (using "bulb")
