Smartphone photography is been helped a lot from creative new apps to improve photography, Star Trails Astrophotography is good proof of this. Just check how my first “Smartphone Stars Trails Photography tutorial” to see how it’s much simpler now!
For starters, the first app is “Intervalometer” which helps to not physically press the shutter button after each long exposure.
Next is the “Light Trails” to combine all the images into one photo. It’s extremely simple to use but it doesn’t stop you from editing it after with Snapseed.
The site that I use to check the light-pollution: https://www.lightpollutionmap.info/