If he's visiting you in your dreams, then he's dreamwalking - and really, you're supposed to get permission from the other person before doing that. Astral travel (or astral projection) is when you leave your body (when sleeping or napping), and no, others can't see you. I've been projecting for most of my life. Mostly it's spontaneous, but I've learned to go at will. And then there were two times that I was seen by different people, during the day, doing what I was planning on doing later in the day. I still can't find an answer for that.