UH Hilo Educational Telescope

The telescope to be installed within the upgraded dome, beginning Late 2008, is presently being built by Equinox Interscience. Below are some photos and descriptions of the work in progress.

The telescope polar axle.

North polar axis bearing.

The 0.9-meter mirror blank, prior to figuring and polishing. The substrate material is Zerodur, an ultra-low-expansion glass/ceramic compound that allows the mirror to operate over a large range in temperature without loosing its figure to thermal expansion. The finished mirror will weigh about 500 pounds.

Polishing lap stone is made from granite and grinds the mirror blank to the specified shape.

View of similar telescope to UHH 0.9m telescope being built by Equinox Interscience

Left, Equinox Interscience President, Russ Mellon, with the UHH telescope polar axle (south end up in this picture). The right ascension drive gear and the tube fork assembly bolt to the flanges on the bottom (north end).

The North polar axis bearing with an assist by UH Hilo Professor Bill Heacox. The weight of the bearing is 320 pounds.

The thick blank (a 6:1 aspect) enables the mirror to hold its figure under varying gravitational loads and will be supported in the telescope by a modified whiffletree, using large triangles that each support smaller triangles as the telescope moves about the sky. This type of mirror cell support structure holds the mirror so gravity won't distort its surface.

The figuring/polishing lap is used to shape the 0.9-m mirror. The material of the lap is granite and is grooved for circulation of the grinding compound. The lap will be placed on the mirror blank and moved across it to produce the desired shape.

A technician adds water to the grinding meduim on the 36" mirror surface in a recent (December 2006) photo. The grinding medium, here, is 9 micron grit. The lens figuring was completed about Christmas, 2007.

The mirror figure testing optical bench. A small lens (at left) is used to distort the beam from a perfectly figured mirror into that of a spherical mirror, which is tested for aberrations by a knife-edge. This is the same procedure that was used to produce the original, troubled, Hubble Space Telescope mirror. They got it wrong by incorrectly placing the lens. The UH Hilo mirror will be redundantly checked to ensure that the problem does not happen to this one.

Telescope fork truss weldment. The load bearing structures are the truss tubes. These will soon be covered with steel skins welded to the surfaces and finished.

Polar axis assembly, with the telescope main drive gears, mounted on base, front view.

Final assembled dome at factory, ready to disassemble, crate, and ship to Hawaii, where it will be reassembled at the summit of Mauna Kea.