The observatory is served by an electrical feed from an outside socket on the side of the house.  This a double switched socket with integral RCD and rated to IP65.  The feed is a 22 metre (72 feet) length of heavy duty three core flex with a 2.5 mm wire cross section.  This flex runs through polyethylene water pipe set a minimum of 30 cm (1 foot) below the patio and lawn with electrical warning  tape above the pipe.  Water pipe was chosen because it is tough, flexible (to a point) and would have no underground joints; thus preventing water and creepy-crawlies getting into the pipe.