One subsystem critical to the performance of a precision electro-optical line-of-sight (LOS) pointing system is a wide-band inertial stabilization reference. This paper compares, in terms of relative performance of LOS stabilization in the presence of vehicle jitter, three inertial LOS stabilization reference mechanizations for space-based optical systems. The three mechanizations are: an inertially stabilized platform, the Inertial Pseudo-Star Reference Unit (IPSRU) under development at Draper Laboratory; a device called the Optical Reference Gyro (ORG), also developed at Draper Laboratory; and a strapdown wide-band inertial sensor assembly. Each of the three stabilization reference mechanizations generates a collimated alignment beam that is injected into the entrance aperture of the optical system. In the stabilized platform mechanization, the alignment beam emanates from a platform inertially stabilized from vehicle jitter in two axes, and thus the alignment beam becomes a jitter- stabilized pseudo-star. An alignment loop closed around the pseudo-star image and a steering mirror in the optical path stabilizes the LOS against vehicle jitter. The ORG alignment beam projects from the gyro rotor, which is decoupled from case motion and is effectively inertially stabilized. The ORG spin-speed noise is compensated with phase-lock technology. In the strapdown mechanization, the alignment beam source is hard-mounted to the vehicle. Inertial measurement of the local vehicle motion is fed forward, open loop, to a steering mirror in the optical path to compensate for alignment beam jitter.