In 64 years there have been a number of Doh! moments, a largish number!
One non-astro moment that gets remembered frequently by so called 'friends', was at a camp site on a prospecting trip years ago.
We always made sure we had a good camp fire going at night, set up with a star post arrangement either side and over the fire for hanging the billy on. First night out the billy was taking forever to boil, so two us hunted around for rocks to bang the star posts down lower, took us for ever!
Eventually we got it done, then one of the wives pipes up, 'why didn't you just get a longer wire to hang the billy on?'
Oh well...
Cheers
Chris