NOVELTY - A transparent/translucent panel unit (30) comprises a series of elongated tubular light-controlling members (e.g. spacer rails (36)) disposed between a pair of parallel spaced transparent/translucent panels (32, 34) and mounted for rotation about their longitudinal axes by applying rotary motion to one end of the member.    USE - For varying the level of light passing through the panel, and joining the panel units to form a transparent/translucent panel system (claimed) for constructing sloped glazing, skylights, roofs and walls and other architectural structures designed to pass light for daylighting interiors.    ADVANTAGE - The panel design provides stronger durability, visual appeal, higher insulation, excellent ultraviolet resistance, and superior light diffusion capabilities, due to smaller spans between rib supports. The internal flexibility of the panels absorbs thermal expansion through the panel in all directions, minimizing stress in all directions and preserving dimensional stability. The panels also have a high impact absorbing and load bearing property, a good ratio of weight to strength and ultraviolet protection on both sides of the panels. The panels are environmental friendly, non-toxic and made of 100% recyclable material. The spacing between the flat panels can be adjusted to accommodate different sizes of light-controlling members for achieving outstanding insulation, soundproofing and structural characteristics with long span construction. Once installed, the light-controlling member can be readily accessed by removing one of the panels, leaving the second panel to protect areas enclosed by panel system from exposure to the outside environment. Use of two spaced-apart panels, houses the drive mechanism between the panels and within the panel unit, out of the way of other structural components. The light-controlling member can be placed in abutting relationship to maximize the effectiveness of the system in blocking incoming light, when the panel system is fully closed. The panel system maintains a perfect balance between light transmission and thermal performance, fostering a daylighted, comforting, livable, and productive environment all year long; and conserves energy on peak demand. Transmission of light across the panel system can be adjusted from full transparency/translucency to total opacity.    DETAILED DESCRIPTION - A transparent/translucent panel unit (30) comprises a series of elongated tubular light-controlling members (e.g. spacer rails (36)) disposed between a pair of parallel spaced transparent/translucent panels (32, 34) and mounted for rotation about their longitudinal axes by applying rotary motion to one end of the member. Each member has at least one light-blocking surface and circular engagement surface in contact with engagement surface of the adjacent member. The rotary motion transmits across the contacting engagement surface of adjacent light-controlling members to rotate the light-blocking surfaces and vary the level of light passing through the panel unit.    DESCRIPTION OF DRAWING(S) - The figure shows a front elevation view of a panel unit attached to adjacent panel units.    Panel unit (30)    Interior panel (32)    Exterior panel (34)    Elongated spacer rails (36)    Clamping system (70)