What it does
My invention is a structure to support large diameter thin mirrors. The stucture utilises adjustable weighted levers to bend the mirror to the correct shape and to counteract gravitational forces. Allowing for nanometre scale adjustment of the mirror surface.
Your inspiration
This project stems from my interest from a young age in astronomy. I have developed a home-made observatory, with a retracting roof system to enable astronomical observation and photography. I also have a strong interest in astrophotography and have developed a portfolio of astro-photos. I have already designed, constructed and successfully employed a number of telescopes. My current large thin mirror based telescope design and development project is by far the most ambitious, challenging and rewarding to date and with a diameter of 515mm, this telescope mirror is likely to be the largest astronomical telescope mirror in Ireland.
How it works
Large thin astronomical telescope mirrors have major benefits over thicker counterparts, including weight-saving and reduced thermal acclimation time. However, these thin mirrors are prone to bending significantly under their own weight, thereby degrading telescope optical performance. To counteract this, I conceived and designed a novel floatation cell to “float” the mirror through radially acting weighted levers. The levers evenly distribute the mirror weight around its circumference. As the telescope is pointed to low altitude angles, the weighted levers edge support the mirror, eliminating gravitationally induced bending. The developed lever system also enables the “tuning” out of intrinsic mirror flaws, such as astigmatism, by independently adjusting each lever length. The levers are evenly spread around the mirror circumference, 7 on top applying tension and 7 on the bottom applying compression. The levers work to eliminate the gravitational effect.
Design process
Through my final year undergraduate project, my floatation cell system was successfully progressed though major development phases of research, concept generation and assessment, through systematic design, model development, advanced analysis and proof of concept prototype design, manufacture, commissioning and testing. Comprehensive finite element analysis validated by undertaken laboratory experimentation clearly established that induced gravitational effects on large diameter thin mirrors are significant in terms of telescope optical performance and require the development of a floating support system to minimise these effects. The floatation cell was designed with roller edge support and low coefficient of friction materials to allow movement of the mirror. An inclination adjustable test rig was designed, developed and commissioned. A Bath interferometer was constructed and applied to quantitatively measure and analyse mirror deflection on a nanometre scale, thereby validating the developed floatation system effectiveness. Extensive undertaken experimentation and generated interferogram analysis and interpretation has successfully demonstrated that astigmatism is significantly reduced by the developed progressive tuning process of the floatation system.
How it is different
The use of thin astronomical mirrors will open up the field of astronomical observation to a much more widespread audience and general public users. The promotion of astronomy as an area of public research is extremely important. The more telescopes that are active, the more likely it is for events to be witnessed, such as meteor impacts on Jupiter observed by amateurs or supernovae in other galaxies or indeed the hazardous presence and movement of increasingly numerous space junk. Sustainability is also at the heart of this design project. By their nature, thin astronomical mirrors are much more light-weight, require less materials and energy to produce and smaller support structures that their more traditional thicker counterparts. A thick mirror is heavy and needs a stronger structure to support it. Also my Newtonian-type telescope, which I have designed and am currently constructing in my family farmyard, is predominantly from recycled materials.
Future plans
Floatation cell design advancements and modifications, including actuator incorporation, are planned to further enhance elimination of induced and intrinsic astigmatisms. Floatation cell has potential in expanding astronomical observation from the elite few to a wider range of people. The design is also being developed to be inclusive of a diverse range of abilities through application of universal design principles. I recently introduced my project to Dr. Neil Murray, Lead Engineer on the European Space Agency’s Lunar Lander Project, who was very interested and highly supportive of my novel floatation system and telescope development work
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