Saturday, August 13, 2011
Create a Timelapse Video of a Meteor Shower
The Perseid Meteor Shower runs from July 17 - August 24, with peak night occurring around August 12-14. When shooting night landscapes and trying to catch meteor showers, I like taking long exposures one after another, so you catch anything which flies through your camera's field of view. If you shoot continuously for a while and catch a couple of hundred exposures or more, you can even assemple those shots into a timelapse video.
Lets do a little math to figure out how your still shots will transfer to video. When deciding how long to shoot, bear in mind that this is a timelapse video, so in playback as video everything is dramatically sped up. Each frame is a 5 to 30 second shot, but video is 24 or 30 frames per second. To make the meteors last more than 1/30th of a second, you may want them to be present for two frames of video, and assemble your video at a relatively slow frame rate of only 12 shots per second, so in video formats that play at 24 to 30 frames per second, the meteors show up for at least two frames. Fortunately our eyes and minds are quick enough for us to perceive the meteors with some persistence even though they show up for only 1/12th of a second.
On a dark night your exposures may be 30 seconds or more, so at 12 frames per second the video displays 6 minutes of shooting time, and an hour of shooting will give you 10 seconds of video. With the nearly full moon last night, there was enough light that I was able to reduce my exposure time to 5 seconds. I set an external timer (intervalometer) to take the next shot one second later, so I took one very 6 seconds, or 10 shots per minute. So if I'm using the slow frame rate trick to make the meteors more persistent, I'll end up with almost one second of video per minute of shooting!
If you'd like to explore timelapse photography yourself, download the free VirtualDub software which can convert a sequence of JPEG files into video, and check out the forum on www.Timescapes.org for discussions on techniques. You'll need a tripod of course, and your sequence of still images will turn out best if you use a remote switch that has an intervalometer (timer) function.