Nice writeup and great observations. For me, somewhere around the level of detail that you captured with your 18" from your new home without a filter (for me - at the remote SQM 21.6 site in 12" with H-beta) the "horse head" begins to devolve into a "notch in IC 434". The separated dark "mane" and the bright tendrils in IC 434 (this took me 16") are what really evokes that feeling that the one from the textbook (likely it was this Malin photo) really exists.