Hubble Optics Primary mirror 406/2032 Pyrex Enhanced Coating (56561)

Hubble Optics Lightweight Sandwich Mirror

The Hubble Optics lightweight sandwich mirror is a cost-effective and high-performance alternative to conventional solid mirrors and other lightweight designs on the market. Its construction is inspired by the design principles used for the Hubble Space Telescope, combining advanced thermal behavior with excellent structural stability to deliver superior real-world optical performance.

Key Design Benefits

• Thermally and structurally optimized open-core design with a dynamically stable closed back

• Extremely fast thermal response, cooling roughly ten times faster than a solid mirror of the same thickness

• Simple flotation mounting for reliable mechanical support

• Approximately 20% lighter than solid mirrors of equal thickness

• Outstanding price-to-performance ratio with a Strehl ratio of at least 0.975

Why Choose a Sandwich Mirror?

Telescope mirrors are manufactured under strictly controlled temperature and humidity conditions and are precisely measured only after reaching thermal equilibrium. During cooling, temperature gradients within the glass can deform the mirror surface, introducing optical aberrations that depend on the coefficient of thermal expansion of the substrate. These aberrations diminish as the mirror cools and stabilizes.

In practice, the primary limitation is not surface deformation but the warm air layer directly above the mirror. This layer causes image distortion known as “mirror seeing,” which results from variations in air density above the warm mirror surface. No mirror, regardless of the glass type, performs at its best until its temperature closely matches that of the surrounding air. Adequate performance is reached when the temperature difference is below 1 °C, while optimal performance occurs when the difference is less than 0.2 °C.

The objective is therefore to bring the mirror temperature to within 0.2 °C of ambient air as quickly as possible. This significantly reduces mirror seeing and improves image quality. For this reason, large professional telescopes employ complex cooling systems. Research has shown that thinner mirror substrates dramatically reduce thermal time lag. The thickness of the glass is the dominant factor in determining how quickly a mirror reaches thermal equilibrium.

A full-thickness solid mirror may never fully equilibrate during a typical observing session, preventing it from reaching its full optical potential. This is a key reason why the Hubble Optics lightweight sandwich mirror delivers superior performance in real observing conditions, even without active cooling. While fans and other active cooling systems can help, they may also introduce micro-vibrations that degrade image quality if not implemented carefully. The sandwich mirror design reaches equilibrium rapidly on its own, providing sharp and stable views much sooner.

Technical Specifications

Optical Characteristics

• Aperture ratio: f/5

• Focal length: 2032 mm

• Surface reflectivity: 96%

• Optical coating: Aluminum with silicon dioxide overcoat

Physical Properties

• Diameter: 406 mm (16 inches)

• Thickness: 53 mm

• Material: Pyrex glass

Product Information

• Series: Sandwich Mirror

• Category: Parts and spares