Good question, thank you. Akasha-chakra is the same as well known Sahasrara-chakra. Gorakhnath in his Siddha-siddhanta paddhati describes 9 chakras and the last is Akasha-chakra, that is located not in the body but above. This is the space to which Kundalini rises to unite with Parama Shiva. Passing through the “gate of Brahma”, Brahmarandhra, you fall into the sphere of emptiness. That’s why it is called Akasha (आकाश — space, void), and sometimes — Vyoma-chakra. The sixteen petals of that chakra indicate to the Moon with its 16 aspects (kala), where 15 lunar days are visible and 16th is transcendent and totally connected with union of Shiva and Shakti. And that kind of experience you can perceive in Akasha-chakra.