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HET

Queue Scheduled Observing

steel balls The HET operates a queue scheduled observing program. Under this system, operation of the telescope, and the acquisition of targets on the nightly observing list is the primary responsibility of the Resident Astronomer, who has flexibility to optimize the observing plan. This mode of operations is particularly well suited to the HET because it makes full use of the entire night for the maximum scientific output. Optimized scheduling overcomes any drawback from the telescope accessing specific areas of the sky only in specific windows of time. The observing program functions superbly for large-scale spectroscopic surveys, rapid follow-up inspections of just discovered, and often short-lived (explosive), astronomical events, and long-term monitoring by periodically re-observing the evolving spectra of some kinds of objects.

truss node Queue scheduled observing brings further significant benefits. It largely "immunizes" participating investigators from bad weather, since the Resident Astronomer has extensive observing time flexibility unlike the irreplaceable time slot awarded to the traditional visitor-observer. Secondly, the observing service provided by a resident observer saves on overall expenses and resources, and avoids equipment-use errors from lack of familiarity on the part of an infrequent visitor-observer.

Amazing Truss

Many systems of the HET are remarkable for their precision and creatively engineered design. The truss supporting the primary mirror array fits this category. The truss was made by MERO Industries, in Wuerzburg, Germany, at extremely low cost. The steel balls shown above were robotically milled into truss nodes, like the example at left, part of MERO's patented connection technique.

The structure is made from 383 nodes and 1,747 struts. Few of the parts are interchangable. The struts were manufactured to a precision of 0.0004 inches, about one-tenth the thickness of a human hair. Before shipment to Texas, the truss was test assembled. Each node in the top surface of the truss was accurate to its theoretical position to better than 0.08 inches.

mirror segments At McDonald Observatory, the pieces arrived in a single truckload and were assembled in six weeks by a MERO crew. Under the dome of the HET, and the 27,000 pound weight of the primary mirror, the truss is deflected just 2.5 millimeters.

Images and Amazing Truss content courtesy of The West Texas Time Machine: Creating the Hobby-Eberly Telescope, Little Hands of Concrete Productions, 1998.

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