Cmc of a miracle

[Jbombard51]

Just wanting to clarify this in my own head, let's say you have {panoptic mirror} in play and you draw {temporal mastery} for an example. Casting it for the miracle cost is considered an alternative cost and not the actual CmC in the case of using the imprint ability correct? I searched a little but didn't dig deeper than a basic search and nothing popped out to me.  Thanks in advance.

[scarsabrex]

cmc is always the top right corner mana cost.