I finally coded a small Android Application to help to position the solar panel and thus avoid calibration of the solar tracker !

Very simple to use:

• attach the smartphone on the panel using the 3D printed holder (or manually !)
• align the sun symbol to the blue line (azimuth orientation)
• align the blue horizontal bar with the two horizontal white ones

and that's it !

The app needs to know your position to compute solar angle at your location. So GPS permission is required...

• Source code is available on my github page
• Compiled Application (.apk file) is available here
• And the 3D printed phone holder is here