 The standard lunar orbit for Apollo missions was planned as a nominal 60 @-@ nautical @-@ mile ( 110 km ) circular orbit above the Moon 's surface . Initial lunar orbit insertion was an ellipse with a perilune of 60 @.@ 0 nautical miles ( 111 @.@ 1 km ) and an apolune of 168 @.@ 5 nautical miles ( 312 @.@ 1 km ) , at an inclination of 12 ° from the lunar equator . This was then circularized at 60 @.@ 7 nautical miles ( 112 @.@ 4 km ) by 59 @.@ 7 nautical miles ( 110 @.@ 6 km ) , with an orbital period of 128 @.@ 7 minutes . The effect of lunar mass concentrations ( " masscons " ) on the orbit was found to be greater than initially predicted ; over the course of the twenty @-@ hour mission , the orbit was perturbated to 63 @.@ 6 nautical miles ( 117 @.@ 8 km ) by 58 @.@ 6 nautical miles ( 108 @.@ 5 km ) . 
