I was inspired by a recent post in the blog Cosmic Focus by fellow amateur astronomy Ggreybeard in Australia. He put his DSLR camera on a tripod facing north and attached an intervalometer. The result was a series of 100 images each 45 sec long stitched together showing the star trails across the northern sky. I encourage you to go visit his blog to see the beautiful image.
I noticed Ursa Major and Minor, the Big and Little Dippers to most people, in the northwest sky in recent summer evenings when I was out with my telescope or binoculars. That post by Ggreybeard made me want to try the same thing. I decided to try to get the star trails using two different camera setups.
My iPad has the app NightCap Camera on it. It can capture many varied low-light scenes including one called Light Trails. I set the iPad on a stable base and started the exposure. It lasted for 1 h 7 m 46 s. Some scattered clouds glided in that were lit up by ground lighting. Airplanes flew over in various directions with blinking lights. The resulting image showed it all. I added some yellow lines highlighting Ursa Major and Ursa Minor as well as Polaris the North Star. It was a messy yet interesting image.
Camera + Intervalometer
While the iPad was busy, I set up my digital camera with intervalometer on a tripod pointed at the same part of the sky. Manual settings included ISO 3200, infinite focus, and 1 sec shutter speed. I knew from tests that the camera would turn off after 3 min and 5 sec of inactivity. I set the intervalometer to capture an image every 3 min and do it 20 times. The 20 images were layered using Pixelmator Pro and the layers set to Lighten. The clouds were present in the last few images and kind of spoiled the shot. But, I could see the trails were readily visible.
The next night was without clouds. I set the digital camera again for 20 exposures. This time the results were what I hope for.