Astrophotography with a mobile phone

I recently upgraded my mobile phone to one with a nice camera (a Samsung S21 Ultra). It has a handy image stabilisation feature on zoom and a nice night mode with long exposures. Turns out it can take quite neat photographs of the night sky even just holding it in my hand with all the resulting camera shake. Here’s some examples:

A starscape from the back garden (taken 2021 April 6). The horizontal lines are not satellites, they’re overhead cables.
The starscape from above but labelled.
The Moon on 2021 April 22.
The Moon on 2021 May 19
The nova V1405 Cas (arrowed!) on 2021 May 10. The constellation of Cassiopeia itself is the big W to the left and below the nova.