Hubble Optics Primary Mirrors 305/1372 Pyrex Enhanced Coating

Hubble Optics' revolutionary lightweight sandwich mirror is an affordable, high-quality alternative to other lightweight solid mirrors on the market. Hubble's sandwich mirrors are similar to those of the Hubble Space Telescope, the most advanced telescope ever built.

• Thermally and structurally optimized open core with a dynamically stable closed design.
• Fast thermal response: cools about 10 times faster than a solid mirror of the same thickness.
• Easy flotation support assembly
• Lighter than solid mirrors (with a weight saving of about 20% compared to solid mirrors of the same thickness)
• Economical with an unmatched price-performance ratio: Strehl ratio >= 0.975

Why should you choose a sandwich mirror?

Telescope mirrors are produced in a strictly temperature and humidity controlled environment. Each mirror is carefully measured after reaching its equilibrium state. When it cools, gradients cause surface deformation. The aberrations induced by these gradients are proportional to the CTE of the substrate. These gradient-induced aberrations disappear when the mirror cools down and is in equilibrium.

However, the main problem is not the aberrations induced by deformation, but the layer of warm air in front of the primary mirror. This layer of warm air is the main cause of image distortion known as "mirror seeing," which is caused by the irregular refractive index in the colder air above the hot mirror surface. No mirror, regardless of the type of glass used, will perform adequately until the mirror approaches the temperature of the surrounding air. This is the case when the temperature difference between the glass and the air is less than one degree Celsius (°C). The best performance is obtained when this difference is less than 0.2 °C.

Therefore, the ultimate goal is to bring the mirror's temperature within +/- 0.2 °C of the surrounding air temperature as quickly as possible. This significantly reduces image distortion due to "mirror seeing." For this reason, all large professional mirror telescopes, regardless of the type of glass used, use complex cooling systems to cool the primary mirror. For example, the 4.24-meter primary mirror of the Advanced Technology Solar Telescope (ATST) uses a jet cooling system.

Based on extensive research, it has been concluded that "thinner substrates drastically reduce thermal response time," technical note #0028 by Nathan Dalrymple. For any mirror, the thickness of the glass cross-section is the primary factor determining the time required to reach thermal equilibrium during observation or image acquisition. A thick mirror might never reach equilibrium and full optical potential. This is one of the main reasons why Hubble Optics' lightweight sandwich mirror has superior optical performance during observation, even without an active cooling system. (Active cooling systems, such as fans, bring serious problems, such as micro-vibrations, which can seriously degrade image quality if not used correctly). Hubble's optical mirrors reach thermal equilibrium very quickly and without any auxiliary equipment.

Key features

Hubble Optics quality for a reliable and rewarding observation experience.

• Type: Kits and parts
• Diameter (mm): 305
• Focal length (mm): 1372
• Aperture ratio (f/): 4.5
• Material: Pyrex glass
• Surface reflection: 96

Main technical specifications