Hey, what a coincidence! I made my first attempts at shooting the moon recently with my 55-250mm as well! I used the same process as above re: zooming in using Live View and setting focus that way. I wish I'd closed my aperture a bit more than I did (yours is very sharp!), but I wanted to keep my shutter speed relatively high as I could actually see the moon moving across screen.
Here are a couple that I'm happy with:
I
blogged about my experience as well
The 2nd pic was taken the night Nasa plew up a rocket on the moon's surface. Unfortunately I was about an hour early
