This camera mount is located on the arm at the top of the top but looks out horizontally across the tower. It captures the profile of the rocket as it leave the rail.
This mount uses the Sony camera shooting at high speed. This is necessary since the rocket passes by so quickly.
The Horizontal Mount actually acts as a counter weight for the other mounts located at the opposite end of the arm. The idea for the Pitch Arm Mount is to place a camera perpendicular to the rocket. However since the rocket is about 1 1/2 feet away from where the arm mount attaches to the tower, a counter weight is used on the opposite end of the arm. The arm was designed so the balancing point of the arm is where the support is located. This helps reducing movement while the rocket lifts off.
The mount was extended above the tower about two feet. From this perspective, the camera can clearly see the rocket leave the rail and pass by the Fixed Rail Mount to see if the rocket hits the mount. Construction of the mount is simple securing the cameras plastic housing to the top of the rail. It can be covered if necessary to protect the camera from overheating in the Sun.