You're right. The OP article contains a line, that they fire the sundial cannon manually as a "fallback": > The 6-pound cannon is fired everyday at 1 PM, from

You're right. The OP article contains a line, that they fire the sundial cannon manually as a "fallback": > The 6-pound cannon is fired everyday at 1 PM, from May to September. On sunny days the sun automatically sets it to light, but on days when clouds obscure the sun, the sun gunner on duty fires the midday salute with a match. I imagine that was what reminded the GP of the joke and I kinda used it as context - but yeah, on rereading, it's not part of the joke. I admit, I jumped to conclusions there.