Lurie-Houghton Telescope
Astrositall Mirror Blank

PHOTO: Astrositall Mirror Blank
This root beer colored ceramic glass compound is Astrositall. Astrositall has a virtually zero (0 +/- 0.06ppm) coefficient of thermal expansion over the temperature range the telescope will experience during observing. This feature provides stable focal length and figure. In this photo most of its figure is ground in and the sag is quite visible by comparison to the metal straight edge. The mirror is 10 inches in diamter and 1.4 inches thick at the edges. It has a spherical figure as required by the Lurie-Houghton design with a radius of curvature close to 89.4 inches. This photo was taken by Mike Spooner of Page, Arizona. Mike is an amateur telescope maker that made the primary mirror and corrector lenses for me.

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Updated: 19 August 2000