Who owns Callanish? Or, more to the point, who has the authority to close it or restrict access. Is it Historic Scotland or do they just manage it on someone else's behalf.

If it's HS they may see this as a potential money earner and limit spaces via ticket sales or the like. Alternatively, if public interest in this grows as it well might, there may be one or more of the "good" nights where they close the site completely to the public to allow a film crew in.

If this happens, it may not be too much of a spoiler as the old (pre-visitor centre) carpark is at the end of the avenue where you'd want to be so views might still be ok.

However, if you really want to be on site it might be worth checking out local knowledge of likely changes to access arrangements before finally fixing on a date.

Just a thought.