I posted the color version of this photo on my Instagram account but I think I like this one better. This is one 30 minute exposure at ISO 160 on a Canon 6D with the long exposure noise reduction switched on. The lens was a Canon 17-40 zoom @ f/4. I've tried stacking 30 second exposures to make star trails before (the most I've done is 180) but really wasn't crazy about how they tuned out. I like this technique better.