EoH: "Osiris is the moon."
I don't doubt Osiris, in later dynasties, became associated with the moon. Indeed, it would have been surprising if he hadn't. But other deities were also associated with the moon: Thoth, Horus and Khonsu. What has to be understood is the role each of these gods played in their association with the moon; what attribute of each of these gods came to be associated with a particular aspect of the moon and its eternal cycle? It is much too simplistic of you to simply state: "Osiris is the moon" because it ignores the particular aspect or attribute of Osiris that the ancient Egyptians related to the moon and its cycle.
As I am sure you know, the sun is regarded as the 'Eye of Re' with the moon being regarded as the 'Eye of Horus'. In AE mythology the cycle of the moon was a powerful metaphor for the death and rebirth of the Eye of Horus. The Eye was stolen by Seth, the god of darkness and chaos and recovered by Horus, the god of order (ma'at) and light. The invisible and dark new moon symbolised the triumph of Seth (and of chaos) whereas the full moon symbolised a return to order (ma'at) from chaos.
Darkness and light; death and rebirth; sleep and reawakening. This is the underlying theme in the scene you present in your post. Osiris is the pre-eminent (re)creator god of everything - the sun, the stars, the Nile, the crops, the king and yes, even the moon. The association of Osiris with the moon is not to say that he is the moon god or god of the moon per se - only that, through the regenerative power of Osiris can the moon (and the sun and the stars etc) hope to be given new life, a rebirth, a reawakening in the same way that the regenerative power of Osiris can give rebirth/reawakening to the kingdom (the earth) and to the king.
In short, it is the particular attribute most closely associated with Osiris i.e. his power of regeneration / rebirth / reawakening of all things, that permits his association to the moon and its cycle (and to everything else). He is the (re)creator god that stands above all others, the god who ensures the rebirth / reawakening of all things.
Edited 8 time(s). Last edit at 12-Jan-18 10:52 by Scott Creighton.