Stacked Star Trails

While camping this past weekend, I took advantage of being out away from the city lights to do some star trails.  The first two nights I shot using a single long exposure of around 60 minutes each time.  For the third night, I changed thing up a bit.  I set my camera up for a 30 second exposure at f/2.8 and ISO 320.  I set the drive mode to continuous and used my cable release to lock down the shutter.  I left my camera alone for the next 2 hours while it ground out 203 images.  I used Lightroom to quickly import the RAW files and convert them to jpeg.  I made no adjustments to them at all.  This gave me 203 images that looked something like this:

By themselves, pretty cool images, but I'm after star trails so I needed to stack the images to create the effect.  I've used a program in the past that works pretty well to stack the images.  It is free and can be found at www.startrails.de.  It's a pretty simple program to use and produces good results.  Did I mention it's FREE?  After processing the image, I imported the tiff file into Lightroom and made some minor adjustments to the contrast and fill light.  I did not have to do any noise reduction.  Here is the result:

I must say, the results are pretty fantastic!  After running this, I got to thinking about using CS5.  I figured I could open each image individually and stack them manually, but there had to be an easier way.  A Google search led me to a flickr group discussion, which led me to blog.starcircleacademy.com.  The guys at starcircle academy have built a FREE action that basically automates the process of opening each image, copying it as a layer on the background image, blending the layer using lighten and then flattening the layers before starting over with the next image.  It's actually kind of fun to watch the program run and see the trails grow.  as a side note, this action works with jpegs or RAW files.  I decided to use jpegs to save my computer the stress of processing 203 - 20mb files. I imported the resulting psd file into Lightroom and again performed minor adjustments to the fill light and contrast.  Again, I did not need to do any noise reduction.  Here's the result:

Well, whadayaknow, it looks pretty darn similar to the results that I got from the free program.  Interesting.  I decided to run the process one more time.  This time, I removed two of the images that had the brightest foregrounds caused by passing cars.  Here are the results:

Again, I performed minor adjustments to the contrast and the fill light and that's it.  By the way, the streaks across the foreground are people with headlights walking through the frame.  If you look closely, you can also see a satellite passing through.  

The Canon 1D Mk IV and Canon 16-35mm f/2.8 lens were used to create these images.