That's a lovely explanation, even if physically wrong:
• No Sundial at midnight.
• At noon, the sundial points (in Europe) to the north...
• Italian pilots, like the rest of NATO, use time of day to indicate direction. Noon (12 o'clock) is used to refer to either "straight ahead" or north (map's 12).
6 o'clock is used when referring to the opposite direction (one's back) or to the south (map's 6).
Maybe you meant that at noon the sun is to the south of the dial?
I am not completely sure, but I think it is because you in general don't use the definite article 'the' with the noun 'noon', it is just 'noon' and not 'the noon'.
when using 'al mezzogiorno'' you are saying 'at the noon' - 'al' meaning 'at the' for a singular male noun (which 'mezzagiorno' correctly is), however it is not correct English to say 'I eat at the noon'.
If I am incorrect, please correct me.
One more hypothesis to try. I haven't had this exercise for microphone in a while, but I came across a similar one in another exercise, and a user had given a solution that worked there.
Try saying "mezzanotte" instead of "mezzogiorno." I hope this works. Thumb me up if it works, down if it doesn't. If I come across this exercise, I will comment on this thread again.