Lowell Observatory Complete Discovery Channel Telescope Primary Mirror Blank

TELESCOPES

The finished mirror blank (pictured) weighs about 6,700 lbs and is only 100 mm (4 inches) thick. Relative to its diameter, the mirror blank is very thin. Such meniscus mirrors have been used in only a handful of other modern large telescopes. The advantage of such mirrors is their comparatively light weight and their ability to maintain a temperature close to that of the surrounding air as the temperature drops during the night.

by Ed Stiles
Flagstaff AZ (SPX) Oct 24, 2005
Lowell Observatory has announced the completion of the 4.3-meter-diameter (14 ft.) primary mirror blank for the Discovery Channel Telescope by Corning.

After two years in production at the Corning plant in Canton, New York, the nearly $3-million mirror blank will be transferred to a different vendor for the two to three-year polishing process that will yield the ultra-high-precision shape required of the finished telescope mirror.

Lowell Observatory Director Bob Millis noted that achievement of this major milestone in the building of the telescope was achieved on time and within specifications. "Working with the highly skilled professionals at Corning has been a pleasure," said Millis.

The mirror blank was manufactured by Corning in a multi-step process that began with production of multiple boules of Corning's patented ultra-low-expansion glass (ULE). The ULE boules were shaped to correct thickness and fused together to produce a single disk for the mirror blank.

In early 2005, the fused mirror blank went into a large furnace and was slumped over a mold giving the blank its approximate final shape. The process ended with grinding the mirror's front surface to within a couple of mils of the final shape.

"Corning takes great pride in knowing that we have produced a mirror blank which meets Lowell Observatory's requirements and will enable scientists to observe the newly discovered Kuiper Belt, explore the outer solar system, and investigate distant stars and galaxies," said Andy Filson, Director of Corning's Semiconductor Materials business.

The finished mirror blank weighs about 6,700 lbs and is only 100 mm (4 inches) thick. Relative to its diameter, the mirror blank is very thin. Such meniscus mirrors have been used in only a handful of other modern large telescopes. The advantage of such mirrors is their comparatively light weight and their ability to maintain a temperature close to that of the surrounding air as the temperature drops during the night.

However, these mirrors are relatively flexible, and accordingly are supported by an active system that maintains optimum mirror shape regardless of the orientation of the telescope. A mirror of the correct shape in temperature equilibrium is crucial to producing ultra sharp images of celestial objects.

The Discovery Channel Telescope is a joint project of Lowell Observatory and Discovery Communications. When fully operational in 2010, the new telescope will allow Lowell astronomers to enter new research areas and conduct existing programs much more efficiently and effectively. When completed, the Discovery Channel telescope will be the fifth largest telescope in the continental United States.

SPACE SCOPES

Proposed U Of Colorado Observatory Could Image Continents On Exo-Solar Planets

Boulder CO (SPX) Oct 12, 2005
A NASA institute charged with supporting novel space concepts that push the envelope with existing technology has chosen a University of Colorado at Boulder proposal to image distant planets around other stars for a second round of funding.

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