There are some really big superstitions that get developed into a well thought out system that attempts to explain everything that exists. Most of the worlds great religions fall in this category.
... Definitions of faith are a sort of verbal slight of hand thought up to disguise the truth that religion is superstition.
So the main difference between religion and superstition is just several layers of sophisticated verbiage.
I too, like Setanta, found your explanation here on superstition, faith & religion profound.
One other point in addition to your well put views on the difference between Astrology & Christianity is that Astrology isn't capable of the "believe it or go to hell" angle. Because of that, I personally view anyone who claims Christianity "just in case there is a hell" (there are plenty like that although they usually won't admit it) as far more superstitious than those who believe in Astrology.
I generally think of human beings as the one animal on earth that has the power of mind to imagine all sorts of unreality that can still seem real simply by virtue of imagined image.
I am personally not so quick to discount every instance of so-called "paranormal" occurences. In addition, I believe that this metapsychic phenomena can be better explained by the spirit hypothesis than by any other. (Not that this has any relevance, but I just read today that Sigmund Freud once said that if he had his life to live over again he would study parapsychology.)
Despite my views on this however, looking at human behavior as objectively as I can, all paths lead me to support the hypothesis that "God" is the combination of projection and transference of a given culture's (and individual's) ideals and ideal relationships onto an unseen (yet psychically, very real) entity.
On the other side, to quote something I read recently, it's hard to look at the DNA sequence for a particular trait and not say (speaking as a software engineer), "You know, that looks a lot like machine code! And that, in turn, presupposes a programmer, a Creator!" At the same time, this is far removed from the idea of a personal, loving, Christian God who cares about us individually and will somehow rescue us from extermination at death.
To those who do believe: Don't get me wrong, I very much hope that there is a loving God. However, I do believe that religion is very much man-made, and that if God does exist, "he" appears to be absolutely silent towards me, other than in my dreams, hopes and fantasies (though these are products of my mind). I don't say any of this to be disrespectful, and I'm painfully aware of how emotional an issue religion is (I myself grew up in a fanatical Christian group which my family is still a part of), but rather I say it in the spirit of honest exploration.