Here is some food for thought...
http://cometal-comets.blogspot.com/2...ro-camera.html
and this is the best result seen so far, I think tracking and processing used by Alex...?
David Malin Awards
https://www.parkes.atnf.csiro.au/new...oFest_DMA.html
Winner: Alex Cherney
Theme - "Astrophotography with your Smartphone"
"Smartphone Galactic"
The best smartphone wide field I have seen so far.