The new job has expected me to earn my money so I've not found myself trying to capture the night sky for far too long. I've escaped to the French alps for a couple of weeks and I'm trying to catch up on lost time. I've come with minimal kit a QHY8L with a 50mm f1.8 lens and I'm struggling to get it working as well as I've liked. This is a 20s imaging nearly centered on M20:

I'm using EZCAP but I just can't seem to get a nice focus, I've selected a star and used the focus function and the best FWHM I can get is 7, am I approaching this imaging technique complete wrong?
I'd be grateful for some suggestions on how to get a sharper image?
Thanks
Ivor