I have a nice cheap Tamaron they run about $500 new. I bought mine for $150. Here is one on ebay:
www.ebay.com...
Mine extends out to 400mm! It even works great to shoot handheld (must use a super fast shutter speed). Tripod works best.
To me it seems like you may be using a tripod that is being affected by the wind. Take your strap off if needed. Your image is just a little blurry.
You are getting a little wind shake it looks like?
Here is mine I just processed real quick (maybe a little too much).
Also, try to get the moon when it isn't so full. If you have some black it emphasizes the craters and gives more depth. Yours looks like a shiny
coin. Always use 100 ISO, no clouds, and back-off just a step from the full 300. Try to focus on something about a quarter mile away-lock it in manual
focus and look at the moon.