I was just about to buy my core, when I tought, what I want it for, and I said to my self, astronomy, so I ask you today, would the core have a clear beam at night, for star pointing ?
I don't personally have one, but for only $40 you can't really go wrong. If you want more questions answered about the Core it would be better to contact WL's support or even ask around on their forum.
I used to be in to the amateur astronomy stuff. If you are doing any serious observing, down to mag 9 or more, the 5mW Core will be great. With dark sky's and dark adapted eyes you really will NOT want anything brighter.
For informal star parties pointing out constellations and planets, and no really serious folk around, brighter is better.