We are planning a big collaborative experiment on 22nd December 2019, in which you can participate. The 22nd December is the day of the winter solstice and we want to motivate as many users as possible to track the trace of the sun across the sky on that day. The idea is, that you simply point your phone at the sun and submit its orientation along with your location when the phone is aligned. This way, we will hopefully create a huge data set which we will share and which can be used by students to derive data like the axial tilt of Earth.
If you are interested in participating and helping, simply share the information about our experiment (especially on and shortly before 22nd December) and conduct it yourself. The actual experiment and short instructions can be found at https://phyphox.org/sun.