Network Time Calibration

Is it better to synchronize the sensors with the phone time or with astro time?

It is better to synchronize the sensors with the phone time. When you login at the first time, you need to allow the system to access your location when you are using the app. When you add the devices into the mesh network, the system already synchronizes the Astro time to the device automatically. But if you change the location of the device then you need to re-sync the Astro time, because the Astro time is calculated by app automatically based on the geographic location of your project.