1.60m (63”) Glass-Ceramic Telescope Reference Sphere with Precision Mount
1.60m (63”) Glass-Ceramic Telescope Reference Sphere with Precision Mount. I are pleased to offer an extremely rare and unique mounted-and-tested optical element for sale. This is your chance, not only to secure a large and beautiful telescope mirror, but to also secure the custom mount that was recently used to interferometrically characterize the optical surface. The optic was created and used in our optical shop as a reference sphere in the 1980’s and 1990’s. The surface is smooth and easily subtracted from the optical test path. This optic has been used in the large optics industry and successfully employed to create a number of large and complex surfaces. This opportunity is targeted towards large optical fabricators, researchers, universities or groups with the goal of a research observatory.
Note: THE IMAGE IS PHOTOSHOPPED. I am still looking for a shop photo.
Cer-Vit is a family of glass-ceramic materials that were invented by Owens Illinois in the mid-1960s. This material (Cer-Vit C 101) was used for large mirror blanks (up to 158 inches in diameter) for telescopes in, South America, France and Australia. Owens Illinois ceased production of C101 in 1978.
In 1979, we purchased the last large boules of Cer-Vit from Owens-Illinois. From this lot of Cer-Vit, the following large optics were fabricated by our optical shop:
1. The primary mirror for the 2.3 Meter Wyoming Infrared Observatory (WIRO) near Laramie, Wyoming.
2. The 2.3 Meter primary mirror for the Siding Spring Observatory in New South Wales, Australia.
3. This 1.6 Meter Optical Reference Sphere.
The optic was fabricated in the early 1980’s by my father and myself. The optic was generated, fine ground and pitch-polished using conventional large tools. For a number of years, it was used in our optical shop as a reference sphere to test and create optical surfaces. Later the sphere was loaned to an optical shop, where they used the optic in a classical “test sphere” capacity. Although the optic has been used to create a number of optical components, there are other possible uses.
Technical Details of Optic:
• Material: Cer-Vit C 101, Owens Illinois, glass-ceramic
o CTE, Coefficient of Thermal Expansion: -2 x 10-9 cm/cm C [0 to 35C]
o CTE is comparable to: Zerodur, ULE
• Diameter: 1.60m (63”)
• Thickness: 127mm (5.0”)
• Weight: 603kg (1330 lbs.)
• Center Hole: 127mm (5.0”)
• Optical Surface Shape: Spherical
• Radius of Curvature: 6.274m (247.0”)
o Measured in the mounted condition using a laser tracker, Spatial Analyzer
• Sagitta: 51.1mm (2.009”) [depth of curve]
• Coating: None (bare, polished glass)
• Surface Figure (interferometric, mounted):
o Peak-to-Valley: 3.4 um
o rms: 380 nm rms
• Optical Test Data for this Optic:
o 4D 4Sight Surface files, quantity: 100
o U of A Saguaro “.map” files, quantity: 2
• Bevels: Yes, 1cm, radiussed
• Back Surface: Plano-pitch-polished, specular, not final-figured
• Optical Surface Damage: None
• Other Damage: Large Edge Chip (see photos). The mount and the surface figure are not affected by this.
• Live Fractures: None observed
• Bubbles and Inclusions: Yes. Cer-Vit is known for inclusions (seeds, ropes, etc.) This was seen even in the best and largest (4m) telescope mirrors from the 1960’s.
• Cosmetics: The surface cosmetics (Scratch-Dig) have not been mapped recently, however, a handful of bubbles are at the optical surface.
Technical Details of the Mount:
• Mount: Custom, Research-Grade, “Belly-Band”. This mount has been custom-designed and built for this optic only. It holds the optic on edge, optical axis horizontal, while minimizing the gravity-induced surface figure errors.
• Precision steel weldment with massive caster wheels and hard floor supports
• Mount Weight: 317 kg (700 lbs.)
• Padded mirror safety restraints
Mirror Accessories (included):
• Custom shipping crate
• Center-Hole Lift Fixture
• Hard-Shell Protective Cover
Please feel free to ask questions. I am Confident that I can answer any questions you may have.
Due to the size and weight of the items, it will have to be picked up locally or shipped freight. Feel free to arrange shipment through your preferred freight company, or we can arrange for the freight shipment.
Please take a look at all of the provided photos before placing your bid