This is my take on it. The Astral body is the spirit body. In ancient Egypt the mystics spoke of the KA and the Ba, Ba being the Celestial Soul Body; light body template and KA being the Soul essence or seed of consciousness. When one is unaware or fragmented to some degree in awareness of the spiritual reality, the two operate independently. When they are unified they become the Merkaba light body or otherwise known as the Astral Body, the vehicle of aware consciousness.

Initially the BA (celestial soul body) runs on auto pilot processing the unyielded spiritual insights overlooked in daily life whilst one is asleep and dreaming. It does this by producing dream experiences symbolic of whatever is in need of being addressed. The KA also goes on auto pilot as dreaming awareness, and can sometimes actually enter alternate realities (parallel universes etc.) In such cases it can attach itself passively to the alternate body of oneself. This I feel is what is experienced as dreams which are vivid but which have no tell tale sign as being a dream until upon waking up. These other realities may be related to learning lessons without having to actually reincarnate into them. Times contrast of flow between two universes is not necessarily relative. So a whole entire lifetime can occur within a nights sleep in an alternate cosmos and never be remembered due to the non relative time dilation/retention factor. Its also possible that one has many alternate bodies existing in infinite universes parallel to this one which all follow the same synchronised passage of time yet which are experienced singularly as either waking life realities or dreams via the non linear 4th dimension. Sometimes an individual may only exist in another cosmos as a conduit to serve as a lesson deliverer for others whereby they dream that role from another cosmos and the rest is set in motion as auto pilot by the Akashic records < look this up if you are unsure what it is.

By the same token the Akashic Records are the 4th dimension which enables the Lucid reality to function. Whereby all possible things from all the existing base physical realms are recorded/exist as static eternal blueprints (the records are more so the imprint of how many times a soul experiences a certain possibility i.e. deja vu) These possibilities become accessible to the lucid adept as a linear stream of events strung together in the 5th dimension which is independent of physical cosmoses i.e. the Astral realm. One can train themselves to experience the astral Lucid realm at will, however this may bypass learning some of the necessary lessons if they use external props, thereby rendering a greater amount of lessons the next time they dream non-lucidly. Its possible to have lucid dreams before all lessons are learned, this occurs during the intermittent period between the orchestration of the wider linear context relevant to ones growth. If one manages to clear all lessons and become a lucid master they have spiritually ascended. Whereby every night they astral project naturally with full awareness.

There is however the total ascention of the flesh still left to aspire to. This occurs when one is sprtually ascended as well as totally enlightened of the holographic nature of the universe. At this point ones body ascends to the 5th dimension of infinite paradise possiblities derived from the Akashic Field of the entire spance of all possible existences. There are even some reincarnated masters out there who are emanations of this ultimate reality, whom come to balance their objective cosm (of which they ascended from during it's final phase of linear potential at the end of the cosmic cycle in which they lived. This is so that the innocent souls whom would have otherwise ascended form that degrading cosmos, can be harvested via the 5D extension (the master) of the Akashic field into a cosmos of higher potential. This will be experienced as a event of positive deja vu whenever an individual is transferred.

P.S. Erii, I am still compiling my thoughts regarding the method of induction.