Hubble Optics Primary mirror 355/1778 Pyrex Enhanced Coating (56560)

Hubble Optics Lightweight Sandwich Mirror

The Hubble Optics lightweight sandwich mirror is a cost-effective and high-performance alternative to traditional solid mirrors and other lightweight designs on the market. Inspired by the construction principles of the Hubble Space Telescope, these mirrors combine advanced thermal behavior with excellent structural stability, delivering superior real-world optical performance.

Key Design Advantages

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

• Extremely fast thermal response, cooling approximately ten times faster than a solid mirror of equal thickness

• Simple flotation mounting for reliable mechanical support

• Around 20% lighter than solid mirrors of the same thickness

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

Why Choose a Sandwich Mirror?

Telescope mirrors are manufactured under tightly controlled temperature and humidity conditions and are precisely measured only after reaching full thermal equilibrium. During cooling, temperature gradients within the glass can deform the mirror surface, introducing optical aberrations proportional to the coefficient of thermal expansion of the substrate. These deformation-related aberrations diminish as the mirror cools and stabilizes.

However, the primary limitation during observation is not surface deformation, but the warm air layer directly above the mirror. This layer causes image distortion known as “mirror seeing,” resulting from variations in air density above the warm mirror surface. No mirror, regardless of glass type, can perform at its best until its temperature closely matches that of the surrounding air. Optimal performance is typically achieved when the temperature difference between the mirror and ambient air is less than 0.2 °C.

The objective, therefore, is to bring the mirror to ambient temperature as quickly as possible. This is why large professional telescopes rely on sophisticated cooling systems. Research has shown that thinner mirror substrates dramatically reduce thermal time lag. The cross-sectional thickness of the mirror is the dominant factor in determining how quickly it reaches thermal equilibrium. A full-thickness solid mirror may never fully equilibrate during an observing session, preventing it from achieving its maximum optical performance.

This is a major reason why Hubble Optics lightweight sandwich mirrors perform exceptionally well under real observing conditions, even without active cooling systems. While fans and other active cooling methods can help, they may also introduce micro-vibrations that degrade image quality if not carefully implemented. The sandwich mirror design reaches thermal equilibrium rapidly on its own, providing sharp and stable images sooner.

Technical Specifications

Optical Characteristics

• Aperture ratio: f/5

• Focal length: 1778 mm

• Surface reflectivity: 96%

• Optical coating: Aluminum with silicon dioxide overcoat

Physical Properties

• Diameter: 355 mm (14 inches)

• Thickness: 49 mm

• Material: Pyrex glass

Product Information

• Series: Sandwich Mirror

• Category: Parts and spares