由点M(4, π 6 ),可得xM=4cos π 6 =2 3 ,yM=4sin π 6 =2.∴M(2 3 ,2).∴⊙M的直角坐标方程为:(x?2 3 )2+(y?2)2=1.把x=ρcosθ,y=ρsinθ代入上述方程可得:(ρcosθ?2 3 )2+(ρsinθ?2)2=1.化为ρ2?8ρcos(θ? π 6 )+15=0.故答案为:ρ2?8ρcos(θ? π 6 )+15=0.