A planetarium juxtaposes the materiality of its daytime image against a nighttime presence wholly defined by light.

¬ĽAfter location, presence is everything-at least when competing for public and patrons, as so many museums are these days. For architecture firm van Dijk Westlake Reed Leskosky, this was precisely the charge presented by trustees for the design of the Nathan and Fannye Shafran Planetarium, an addition to the existing Natural History Museum in the firm's hometown of Cleveland. Owing to several unique factors, it also became the challenge.

Located on Wade Oval, the Natural History Museum shares its neighborhood with the Cleveland Museum of Art, the Botanical Garden, the Cleveland Orchestra's Severance Hall, and most recently, Frank Gehry's Peter B. Lewis Building for Case Western Reserve University. Each has an impressive nighttime presence, and the trustees wanted the planetarium to communicate a message that could compete with these significant cultural structures. Unlike its neighbors, however, the new addition required a windowless exterior to protect the integrity of its exhibitions and projected presentations. The planetarium's outdoor lighting scheme also needed to defer to the observatory located at the museum; any spill light would interfere with stargazing.

Conceptualizing the planetarium's daytime demeanor also proved difficult; the best location for the building was at the entrance of the museum, which meant it had to welcome visitors and announce the institution's purpose-without actually being the ingress. Often, explains Paul Westlake, managing principal of the firm and lead architect on the planetarium, designers have light and glass or the interplay of glass and a solid material as the primary media with which to design a building's entry. 'But a planetarium wants to be a windowless form that is circular in plan. Its most efficient shape-but not necessarily its most elegant-is probably a drum. We had to create a signature identity with forms that were solid and that had the potential to be awkward if not carefully sculpted.'

The planetarium required 'two different jackets,' says Westlake. 'The structure needed a presence by day and a presence by night.' The 'jackets' the design team chose speak directly to a separate-but-equal approach to materials and light, to a respect for both as distinct parts of a whole.

During the day, the planetarium's glinting bronze-colored facade primes visitors for the tale it will tell inside. Soft and workable, bronze and brass were used in the early days of astronomy, long before steel and aluminum (think Copernicus and Galileo), to create the instruments of planetary science, such as telescopes and sextons. Westlake admired the antique instruments machined from these alloys in the museum's collection and wanted to create a similar effect architecturally. There was one problem, however: copper-based alloys oxidize, acquiring a verdigris patina. After months of materials research, the team finally specified a titanium sputtered stainless-steel product from Japan. The titanium (which is inert and will not change color) is ionized; an opposite charge is applied to it and the stainless steel; and the two are fused together in a vacuum. A customized color simulating bronze was added to the material.

The architecture's deference to the instruments and program it houses does not stop there. Oriented to the North Star and designed with a chamfered roof, the planetarium is an astronomical tool in itself. The long axis of its ellipses is arrayed to polar north and the roof is angled to Cleveland's latitude (42.5 degrees), enabling a viewer with a sightline coplanar to the tilted roof to find the North Star.

At night, however, the luminous bronze form-which seems 'to hold sunlight'-disappears. There are no windows to define the building, and given its reflective skin, floodlighting the planetarium would have washed out the facade surface, as well as interfered with the nearby observatory. The building required a delicate treatment that both highlighted its distinctive form and respected the night sky.

'We had the idea of a 'sequined' jacket,'' says Westlake, whose firm also designed the lighting for the project. 'It would be a form articulated only by dots of light': in essence, little electric stars. The designers considered a fiber optic system immediately, primarily for its energy efficiency and straightforward maintenance: There are six illuminators-all easily accessible by the maintenance staff for relamping-that power the facade's more than 400 points of light. Each illuminator contains a single 150W metal halide lamp, which was specified for its long life, further simplifying upkeep of the system. Choosing the right fiber optic strand proved more complicated. The light points on the metal skin were not to be any brighter than the brightest star in the sky, so the design team arranged several mock-ups during the fall months when the stars are most visible because of the limited moisture in the atmosphere. 'We were amazed at how intense the fiber was; it hardly took anything to be visible from a quarter of a mile,' Westlake recalls. Ultimately, they settled on a small 1/8-inch-diameter strand, eliminated end caps because of their bulbous effect, and fitted the illuminators with perforated wheels to filter out a bit more of the emitted light. The effect: geometrically arranged pinpoints of light that seem to gesture toward the sky and their more chaotically dispersed brethren.

The interior tunnel is also illuminated with fiber optic strands, which are sandwiched between a black-painted wall and perforated metal scrim. The effect: Visitors walking through the passageway feel as if the strands are floating.

Inside, fiber optics also outline the 50-foot passageway that connects the museum entry to the new planetarium and its exhibit hall, enticing and acclimating visitors as they approach. The designers wove approximately 50 fiber strands together-in a random configuration that suggests 'calculated chaos'-along the ceiling and sides of the hexagonal corridor (a shape taken from the primary donor's favorite sci-fi movie, 'Forbidden Planet'). The strands are encased between a perforated metal scrim and black-painted walls, and woven at different depths through the perforated fins that hold the scrim in place, creating an illusion of infinite space interrupted only by light since the planes of the wall and scrim are not discernable. To raise the light level slightly, a dozen strands running along the ceiling were sheered off and inserted through the metal scrim for downlighting. In addition to an auditory element, visitors experience subtle shifts in the brightness of the fiber optic threads and the light points on the floor; the strands are randomly attached to five DMX-controlled illuminators fitted with filters that slowly change the amount of light emitted from the source. Westlake notes, 'The corridor feels like it's pulsing.'

The passageway-defined almost entirely by the fiber optic strands that stretch its length-draws on the lighting expression of the facade. (The bronze-colored metal skin with its fiber optic pinpoints briefly appears inside, where the conical planetarium connects to the exhibit hall.) The exterior, however, represents much more of a give and take between materials and lighting: 'During the day, it is a solid object, with no sense of light,' says Westlake. 'You don't see the fiber optics at all. It's as if the thing were machined out of poured bronze. At night, however, you have absolutely no sense of the bronze metal; you only read the shape of the object by the light-sort of in the same way the constellations are read.' For the planetarium, facade material and lighting are each inherently dependent on, and yet distinctly separate from, the other, like an architectural Dr. Jekyll and Mr. Hyde; when one is present, the other is absent, and yet it is the characters' coexistence that forms the whole.
emilie w. sommerhoff

project Nathan and Fannye Shafran Planetarium, Cleveland Natural History Museum
architect/engineer van Dijk Westlake Reed Leskosky, Cleveland
construction manager Gilbane Building Company, Cleveland
metal skin consultant A. Zahner Company, Kansas City, MO
photographer Hedrich Blessing/Nick Merrick
cost $6.9 million
manufacturers Super Vision International, Lumenyte, Cooper Lighting, Concealite