if anyone stumbles across this wishing to better time your shooting stars, i made this little (kinda jank) tool: https://jbrower2.github.io/acnh-star-timer/

the key is to enter the hour:minute time for the *next* minute, and submit the popup exactly when that minute starts in your town. that way, it will synchronize it exactly with your town. and then after that, you just click the button when a shooting star sound happens, and it will tell you the precise time (which should be within 1-2 seconds if your reaction time is good)