I have tried star trails photography once before—7 years ago. Back then I was using the D70 which was a good camera but there were two problems with it for astrophotography: first, its CCD sensor wasn’t the best at higher ISOs, and second, long exposures were not possible because of some interference (thermal or electric) which resulted in ugly purple fringing. That experience made me not really bother with astrophotography—hence the seven-year hiatus.
A week ago I decided that I should try again with my D750 and the 24-70mm f/2.8 lens. Since they are both significantly newer than my old setup and are superior in just about every way, I thought why not try again and see exactly how much better the results would be.
I ended up with only three shots worth sharing. As always, I made a gallery with them. The one difference from the other photo galleries I make is that I will continue to add star photos to this gallery until the end of the year (when I plan to make a 2017 gallery).
After setting up the camera in the general direction of Polaris, I needed to figure out the exposure. So, I cranked up the ISO to 10000 and took a 5 second test shot at f/2.8. The hope was to see how the sky exposed, and then “trade” the ISO for time to get the same exposure but less noisy and with star trails. (E.g., changing the ISO from 10000 to 160 is 6 stop difference, so the shutter speed needs to change 6 stops in the other direction to compensate. That is from 5 seconds to 320 seconds.) When I viewed the image on the back of the camera, I was blown away:
While there is certainly noise in the image (which you can’t see in the resized version) and the composition is not great, it’s cool how both the foreground and the sky are equally well exposed. The trees are essentially light-painted by the neighbor’s driveway lights which were on at the time. And before you ask, no, that’s not the milky way, that’s just a wispy cloud.
Then, I proceeded to take a back-to-back series of 15 second exposures. After five minutes (21 shots), I was sufficiently bored to try something else. After heading back inside, I stacked the 21 shots using StarStaX. Here is the resulting image (slightly tweaked in Lightroom):
The orange blur on the right of the image is a small cloud that moved across the frame during the five minutes without me noticing. Unfortunately, there is plenty of light pollution to the northeast of us because of the neighboring city of Nashua. I am definitely going to experiment with stacking.
The final couple of shots I took were all various long exposures—ranging from 8 to 20 minutes. This is one of the 20 minute exposures:
Again, the light pollution from Nashua is unfortunate.
The 74 degree horizontal field of view at 24mm is pretty good. Of course, a wider lens would provide for an even more interesting shot. For example, a 15mm focal length would produce a 100 degree horizontal field of view. With that said, I am certainly going to experiment more with star trail photography—even if I have “only” a 24mm focal length.