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A Technical Description of the Lighting System by Elsa Garmire

Drawing by Tony Martin of the Lighting system

Tony Martin's drawing for the lighting system in the dome.



The versatile lighting system in the dome is designed to make full use of the optical properties of the spherical mirror.  About a third of the way down from the top of the dome are three groups of lights, 120° apart.  In each group are two 1-kw tungsten iodide lights which illuminate specific areas of the floor. A compromise between flood and spot light, the area of the floor each brightens is about 8 feet in diameter.  Specific areas illuminated are: tile, bounce, rough wood, carpeted steps, stone and asphalt.  The intensity of these lights is controllable by manual, audio, paper or magnetic tape signals from the control room but their direction is fixed.


In each light group is also one automatic color, automatic iris, variable intensity, one-kilowatt spotlight with controllable direction.  These air-cooled quartz iodide lamps are intensity-controlled by SCR's in the control room and contain three color-gels.  Each of these spotlights is located on the other side of the mirror and bounces off an automatic, motor-driven, pan-tilt, dual-faced mirror so that the direction of the beam is completely controllable.  These super-controllable spotlights serve two basic functions:  They light varying sizes of groups  of people or individuals to take maximum advantage of the reflected real images, virtual images and their additional secondary real and virtual images produced by reflection.  Secondly, they can dynamically activate the space because of their great flexibility.  They are programmable through a paper-tape machine and/or tape recorders and/or audio or other sources. All functions can also be performed manually from the control console.


At the equator are two Xenon arc spotlights on opposite sides of the dome.  These produce 75-watt, well-collimated, six-inch diameter, high-intensity beams.  The design of these lamps is similar to the larger ones forming the light frame on the outside of the Pavilion.  These beams are sufficiently narrow to travel through space, and bounce off the mirror. Several reflections are possible from the good quality mirror, forming light structures in space inside the dome.  On-off switches are located in the control room and the beam direction is hand-adjustable.


The remaining light source is suspended on a winch from the top center of the dome.  This source is automatically moveable from one meter off the floor to two meters from the top of the dome, through the mirror's focal point.  The light source contains three 1-kw bulbs mounted in a hemispherical reflector facing upwards, so as to provide an apparent 3-kw point source of light.  This source provides means of covering much of the mirror dome with light at one time.  When it is positioned near the mirror's focal point (half-way to the top), pure white light without images is reflected directly from much of the dome at a time.  This provides a way of "turning off" the mirror with light so that a person can no longer see reflections.  He sees instead huge blossoms of light.  The intensity of this source is controllable manually or by paper or magnetic tape, audio or D.C. inputs through an SCR in the control room.


All light controls can be handled automatically in the control room.  Complex automatic operation is possible through a 42-channel punch paper tape machine which handles pre-recorded switching information.  These switches include on-off to tape recorders for all variable functions and on-off operation for the non-variable functions.  The switches control the light intensities for the nine lights near the top;  three color gels, iris and pan-tilt for three lights; winch light intensity and position, and two Xenon arcs.

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