the dream world is the mental plane.. the astral plane is like a zone that girdles the material earth and the zone of the planetary spheres.. this is where the immaterial beings (like the souls of the deceased persons and other entities such as the gods and the genii) inhabits.. this is also the plane where you, after you have been experience the so-called death will go (depending on the level of maturity of your soul)..
"the astral plane is a vibration-sphere and it is the origin of light, sound, color, rhythm, and life in all thins created.. all that ever was produced, is being produced and will be produced in the future is reflected in it.. the adept who sees his way about this plane may find everything here.. no matter if the point in question be in the past, the present, or the future.." - from the initiation into hermetics of franz bardon..
now, someone you here will ask (well actually me too is still asking myself), so if you did (wait!! i'm not the one who said it, i've just quoted it from franz bardon's book.. lol) say that in the astral plane, you can see everything in the past, the present, or the future but why can't someone really predict the so-called "end of the world?" my answer is this, there are many adepts from the pasts who have actually predicted this so-called end of the world.. and i don't know.. i've visited the astral palne (and its merely an accidental thou) just twice thou so i can't really answer.. (my own question too).. and astral porjection is not in my practice yet.. lol..