It has been a great honor for Hubble Optics to work with the Alt-Az Telescope Initiative led by Russell M. Genet and now we are proud to announce the introduction of the HNA as the result of this collaboration. In particular, we are grateful to Dave Rowe for his excellent HNA design.
The combination of a lightweight sandwich hyperbolic primary mirror and a matching custom corrector provides excellent wide-field performance for both visual observation and astrophotography, with numerous advantages over existing solutions:
· Superb on-axis image quality, with a Strehl ratio greater than 0.99.
· Much better overall performance than a parabolic mirror with a Ross corrector.
· Meets the polychromatic performance of a parabolic mirror with a Wynne corrector, with much fewer problems from ghosting, baffling, and reflections.
· The corrector takes up less space, and has sufficient back focus of 130mm for easy insertion of off-axis guiding hardware and filters.
· Excellent optical performance for both wide field visual observation and astrograph at an unprecedented price/performance ratio.
The HNA corrector will be initially available in 3.5-inch versions with a Hubble Optics lightweight-sandwich primary mirror, 14-inch, 16-inch, 18-inch and 20-inch. The delivery time is about 2 months. The complete optical set includes a lightweight-sandwich hyperbolic primary mirror, a high-quality secondary mirror, and a matching custom corrector assembly.
Why Hubble Lightweight-Sandwich Mirrors?
Telescope mirrors are manufactured in a strictly controlled temperature and humidity environment. In particular, each mirror is carefully measured after it has reached equilibrium in our laboratory. This is not the environment that your mirror will be used in. While cooling, gradients in the mirror will cause deformation of the surface, and the aberrations induced by these gradients will be proportional to the CTE of the substrate. These gradient-induced aberrations die out as the mirror cools and equilibrates.
The main problem is not the aberrations due to deformation, but the layer of warm air in front of the primary mirror. This layer of warm air is the main cause of the image distortion called "mirror seeing", which is caused by the non-uniform index of diffraction in the cooler air over the warm mirror surface. No mirror, regardless of the type of glass used, will perform adequately until the mirror is close to the temperature of the ambient air. This occurs when the temperature difference between glass and air is less than one degree centigrade (°C), and best performance is achieved when this difference is less than 0.2 °C.
Therefore, the goal is to bring the temperature of the mirror to within 0.2 °C of the ambient air temperature as quickly as possible. This will greatly reduce image distortion due to mirror seeing. This is why all large professional mirrors, regardless of the type of glass used, employ complicated cooling systems to cool the primary mirror. For example, the Advanced Technology Solar Telescope (ATST) 4.24-meter primary mirror uses a jet cooling system.
After years of research, ASTS concluded that "thinner substrates dramatically reduce the thermal time lag", Technical Note #0028 by Nathan Dalrymple. For any mirror, cross sectional thickness of the glass is the primary factor in determining the thermal time constant. As a rule of thumb, the magnitude of the thermal time constant is roughly proportional to the square of the thickness of the glass. So, with ever-changing temperatures during observing or imaging, your full thickness mirror may never reach equilibrium, and never reach its full optical potential. This is one of the major reasons why our lightweight-sandwich mirror has superior optical performance in real world situations, even without an active cooling system. (Active cooling systems, such as fans, introduce their own serious problems, such as micro vibration, which can seriously degrade the image quality if not done correctly.) Our mirrors reach equilibrium extremely fast, and without aid.
So, with our lightweight-sandwich mirror, what is measured in the laboratory is observed in the field.
Shipping and Handling
The mirror will be shipped to you directly from Hong Kong.
The Hubble Optics Sandwich Hyperbolic Primary Mirrors are priced at:
14.0" F/5.3 $1300
16.0" F/4.7 $2000
18.0" F/4.2 $2900
20.0" F/3.7 $4000
All primary mirrors will have the same focal length of 3800mm.
The primary mirrors will be 0.95 Strehl wave front or better, 96-98% enhanced coated.
The HNA matching 2-element corrector optics with 99.5% broadband AR coating is priced at:
For More Information: