As far as C&C, again for a first attempt, I think it's well done. Just looking at it this morning, the original does look a bit over-exposed and was lacking in sharpness, but the edit does look better. Looking at the exif data, it does look like the aperture was set f.6.7....I might stop that down just a hair. Not sure about Olympus lenses, but more often than not a lens's "sweet spot" is usually around f/8'ish...it -might- give you just a bit more sharpness. Also, without seeing the original it's a hard call and I'm not really familiar with Olympus lenses at all, however with many of the 70-300mm lenses I've used, they can get a bit soft on the long side...it might be worth trying a bit less zoom, then cropping in...again it might give you just a bit more sharpness. This is just my own opinion, but with stuff like astro and lunar photography, every last bit of edge you can get regarding sharpness usually helps.
Now I can't speak to others, but again in the case of my own shot up there, I did use a small telescope for mine along with a program called "AstroStack"...I do a bit of the amateur astronomy thing and would very much like to get into some more serious astro-photography work at some point, so it's a nice program to have. That said, I'm pretty sure there's still some free stacking programs out there (Registax for example), so for anyone interested in stuff like lunar or astro photography, it might be worth looking into...good stacking software does a couple of things that Photoshop doesn't.
Just my $.02.