Hi Tony,
Welcome to the game
Good first attempt. Well done
Which scope were you using to take this shot ?
Are you using any tools to focus ?
If you want greater clarity in your final result, use more subs. Try capturing 100 or so to start with then grow from there.
My mount isn't very good so I can't get longer than about 25sec subs but it appears from your signature you have some really nice stuff. You should be able to capture much longer exposures than 15 seconds.