A passive suspension system for supporting an instrument relative to a rigid support structure while preserving angular alignment of the instrument. The suspension system includes an instrument platform, the instrument being secured to the platform, and first and second vibration isolator systems. The first ends of the isolator systems are attached to the rigid support structure so that axes of the vibration isolators extend transverse to the instrument axis. The first and second isolator systems resist motion transverse to the instrument axis and provide shock and vibration isolation transverse to the instrument axis. First, second and third stabilizing struts extend parallel to each other and the instrument axis, and are of equal length. A first set of bearings connects ends of the struts to the instrument platform in a spaced relationship, and allows motion transverse to the struts. A second set of bearings connects opposing ends of the struts to the rigid support structure in a spaced relationship. The second set of bearings permits motion transverse to the struts.