Red light, white light: How to preserve your night vision while using stargazing apps

The best stargazing apps can take your observation of the night sky to the next level, whether that's using augmented reality (AR mode) to identify stars or looking up the next lunar eclipse. However, the bright light emitted by smartphone screens can prevent your eyes from adjusting to the dark. If you're using one of the best telescopes, you'll want to preserve your night vision even more. Fortunately, there are ways to all but eliminate this problem.Why are bright screens bad for stargazing?T