If i'm not mistaken, in Dragon's ball comic, the moon were destroy twice. 1st from Master Roshi ( when Son Goku turn into Giant Ape ) and then Piccolo.



Remember when Master Roshi destroys the moon in dragon ball,the average distance between the moon and earth is 384,392 kilometers(238,857 miles),now let's assume it takes max 5 seconds for the kamehameha wave to reach the moon,than the speed of the kamehameha wave would be an incredible 76880.6 kilometres per second(47771.4 miles per second),the speed of light is 300,000 kilometres per second and this makes Master Roshi's kamehameha 1/4 speed of light, imagine gokus kamehameha in saiyan saga let alone frieza saga.