While I have been lucky enough to have a couple opportunities to photograph the Milky Way during my photographic travels over the last couple years, there was one type of wide field Astrophotography which I had yet to try. Capturing the movement of the stars requires more planning and a lot more time to photograph than a still of the Milky Way, though the requirements for equipment can actually be a bit lower. For the Milky Way, every second that passes causes the undesired effect of star movement, meaning that the stars near the edges of the frame will become little lines instead of points of light. To fight this, you want the fastest, widest lens you can afford and fit – and even then you still need to turn the ISO up to 1600 or higher to capture the details of the galactic core. By contrast, when shootingstar trails, it is exactly the movement that would ruin a Milky Way shot that you are wanting to capture. So longer exposure times, often 30 seconds to a minute each, are not a problem. Realize however, that because the stars are moving, there is only so much light that will enter at any single point as the stars rotate through the heavens – so there is a limit to how far you can turn the ISO down or stop the aperture down to and still capture enough stars to fill the sky.
During my April photo trip through the Hill Country region I knew I would be far enough away from major city centers to have dark enough skies to make an attempt at a star trails photo. However the weather wasn’t being very cooperative during the first half of the trip and it wouldn’t be till I arrived at Pedernales Falls State Park outside of Austin that the skies finally cleared for an evening. I got a tip from the park host that these old barns still stood from when the park was ranch land on the edge of the equestrian parking area. This location made for a great foreground for setting up my star trails composition, and being able to park only a few feet away meant I was able to pass the 90 minutes needed to take this photo from the comfort of my truck.
Utilizing the ultra-wide Rokinon 14mm f/2.8 lens, a fairly inexpensive manual lens that is very well suited to wide field Astrophotography, I opted to stop down to f/3.5, just to allow for a tad bit more depth of field and sharpness compared to fully wide open. ISO was set at 800, and each photo would be 30seconds, the longest I could set using the Manual mode on the Canon 6D. While I could have used my intervalometer to get longer exposures, 30 seconds would be plenty to get the star movement and prevent extra noise caused by longer single exposures.
Ultimately I would take 268 frames at Pedernales Falls State Park, that didn’t include the 3 photos I took right after setting up the camera before the sun fully set, allowing me to get the photo I ended up using for the foreground. The last gasps of sunlight, reflecting through the atmosphere, provided just enough light over 20 seconds to show up as an even golden lit foreground photo. Back home, all photos were imported into Lightroom where I did initial exposure adjustments, I actually needed to reduce the exposure on each photo just a touch to get a deeper black sky. After exporting all the photos to TIFF format, I used StarStaX to do the star trail layering, and then in Gimp to blend in the foreground. Final adjustments were then done back in Lightroom.
Future plans for this photo include doing a new foreground blend in Photoshop where I hope to be able to do a better selection of the barn and tree for a cleaner blend. Also going to investigate what I can do to remove or at least reduce the appearance of the aircraft trails.