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8.4-Meter Mirror Successfully Installed in Large Binocular Telescope
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(from uanews.org)
 Steward Observatory senior staff technician David Sakacs works on integrating the mirror and its support cell. The upright structure next to the mirror, which is covered with protective plastic, will support interchangable instrument packages. (Photo: Lori Stiles, UA News) |
The University of Arizona today
announced that the first 8.4-meter (27-foot) primary mirror for the world’s
most powerful telescope, the Large Binocular Telescope (LBT), has
successfully been installed in the telescope structure at Arizona’s Mount
Graham International Observatory (MGIO).
The 18-ton mirror made its 150-mile journey from Tucson to the top of Mount
Graham near Safford, Ariz., in October 2003. Now the mirror has been
installed in the telescope, and technicians are testing intricate mirror
support system hardware and software in preparation for telescope "first
light." First light, or when the mirror collects its first celestial light,
is expected later this year.
The deeply parabolic mirror was cast and figured at the University of
Arizona’s renowned Steward Observatory Mirror Lab and is the first of two
identical giant mirrors that will make up the LBT. The mirrors are much
larger and lighter than conventional solid-glass mirrors used in the past.
Both together are valued at $22 million.
 A red-painted C-ring casts a glow on plastic covering the LBT's first mirror. C-rings bear the weight of the mirror and support cell in the telescope structure. (Photo: Lori Stiles, UA News) |
Each LBT mirror is a "honeycomb"
structure made out of borosilicate glass that was melted, molded, and spun
into shape in a specially designed rotating oven. Once cast, the first
mirror was polished to near perfection using the Mirror Lab's innovative
"stressed-lap" technique. The mirror surface matches the desired shape to
within a millionth of an inch over its entire surface. The Mirror Lab is
currently polishing the second primary mirror.
After the first mirror was moved to the telescope structure late last year,
engineers spent more than two months testing and perfecting mirror
installation procedures using a dummy mirror in the actual mirror "cell," or
mirror support structure. The mirror was then installed in the cell and, in
precise operations that required maneuvering the mirror and cell through a
hatchway between building floors with only inches to spare, LBT workers
lifted the mirror onto the telescope structure. The telescope is housed in
an innovative 16-story rotating enclosure.
 Ground-level view of the LBT. The mounted mirror cell in its horizontal position is visible to the right of the closest giant C-ring. (Photo: Lori Stiles, UA News) |
John M. Hill, LBT Project director,
said, “This is a huge step in what has been a very long and challenging
process and would not have been possible without the support of a great
team. From construction of our unique telescope structure to the
implementation of this massive mirror, every step has involved great minds
using cutting-edge technology. The remarkable success we have had so far is
a tribute to the creative efforts of our team members.”
Work on the $100 million LBT project began with construction of the
telescope building in 1996 and will be completed in 2005. The project is
entirely funded by the LBT Corp., an international consortium of scientific
and academic institutions. When the LBT is fully operational, it will be the
world’s most technologically advanced optical telescope, creating images
expected to be nearly 10 times sharper than images from the Hubble Space
Telescope.
 Sunset at the LBT. (Photo: John Hill) |
Peter A. Strittmatter, president of the LBT Corp.,
said, “The twin mirrors of the LBT will have the light gathering
capabilities of an 11.8 meter (39-foot) conventional telescope. This is an
exciting time for everyone who has been involved in this pioneering effort.
The LBT will provide unprecedented views of our universe, including for the
first time, the ability to image planets far beyond our solar system. I
believe this is the first of the next generation of extremely large
telescopes and will signal the beginning of a new golden era in this type of
space exploration.”
The LBT project is managed by the LBT Corp., a partnership that includes the
University of Arizona; Ohio State University; the Research Corp.; the LBTB,
a German consortium of astronomical research institutes; and the INAF, the
Italian National Institute for Astrophysics. The LBT Corp. was established
in 1992 to undertake the construction and operation of the LBT.
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