The Castle-Emerald Company, llc


Telescope Mirror Blank Kits for the Quality-Obsessed Amateur Astronomer



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About The Castle-Emerald Company


We are a West-Michigan based company dedicated to serving the Amateur Telescope Making (ATM) community with the highest quality mirror fabrication kits available anywhere in the world.  Each and every component of our kits is chosen strictly on the basis of quality to ensure that not only will ATM’s spend fewer hours laboring and encounter fewer problems, but that the finished mirror is of the absolute highest quality substrate available.


We believe that the one group of people who deserve most to have access to the highest quality mirror blanks is the ATM.  It only makes sense that those who desire perfection the most and are willing to work for it should not have to settle for overpriced inferior glass.  We endeavor to not only supply the highest quality blanks anywhere in the world, we also try our best to fulfill our customers’ requests, no matter how unusual.


Why Should You Make Your Own Telescope Mirror?


While it is true that the last 20 years has seen impressive strides by commercial telescope manufacturers in offering higher and more consistent quality telescopes at ever decreasing prices, these price-point instruments still pale in comparison to those fabricated by hand by inexperienced amateurs.  Sir Isaac Newton, upon grinding a tiny mirror (a mere 1.3 inches in diameter) for his first reflecting telescope, found himself with small compact instruments that rivaled even the largest and most expensive refractors of his time and set forth a revolution in astronomical optics that continues to this very day.  Mirror substrates steadily improve, as have reflective coatings and fabrication methods, but Newton’s basic design has weathered the test of time as the most cost-effective and powerful optical system for amateurs to construct.

            There is no single task in building your own telescope that an average person should find difficult.  It is true that there are many steps to success and scores of decisions to make along the way, but EVEN THE COMPLETELY INEXPERIENCED AMATEUR CAN PRODUCE AN INSTRUMENT OF FAR HIGHER QUALITY THAN CAN BE PURCHASED FROM A MANUFACTURER, AT ANY COST.

            In the realm of optics it is still nearly impossible to avoid getting what you pay for; try going cheap and the quality will suffer.  The reason for this is simple; machines cannot figure optics to any degree of requisite quality.  High quality optics requires labor and will invariably cost more.  Additionally, the higher the quality of the substrate, the more energy is required to manufacture it.  These costs cannot be avoided.

A quality instrument for observing astronomical objects requires optics that have been fabricated to extremely high degrees of both form and polish.  Despite any notion you may possess, THERE IS NOTHING DIFFICULT TO ACHIEVING BOTH; it just takes time and care.


About Our Products


We supply only the highest quality substrates in our kits; namely, the precision-annealed borosilicate “Supremax-33”  and the glass-ceramic “Zerodur”.


Supremax-33 is the highest quality glass substrate available with an ultra-low thermal expansion coefficient.  It grinds fairly quickly and takes an exquisite optical quality polish.  Nearly chemically identical to the well known Corning Pyrex material, Schott Supremax-33 is the rolled and precision-annealed version of Borofloat-33.  Additionally, our Supremax-33 blanks undergo a re-annealing process which drops the strain to less than 6mµ!  This is important because when glass is manufactured, it invariably includes internal stresses (which are impossible to avoid) and as these stressed regions exert internal pressures within the glass, they act to deform the mirror over time.  During the re-annealing cycle that our blanks are subjected to, these strains are allowed to ease leaving a blank that will not deform over time.


Zerodur may look like glass, but is actually a ceramic; a homogeneous mixture of glass and crystalline ceramic.  It’s coefficient of expansion is essentially zero, making it the highest quality mirror substrate mankind has ever produced.  Zerodur grinds and polishes much easier than quartz, making it more attractive from a labor perspective.  It is pricey, but this is the stuff that will be used in every professional observatory constructed in the future.


In addition to these high quality substrates, all blanks are custom pre-generated with a curve of your specification, saving you around a third of the total labor over a traditional flat blank.  High durability porcelain hex tiles and dental stone are included for construction of your tool.  With each stroke, you will grind more of your mirror than you would with a traditional glass tool, saving even more labor.  You will find no cheap burgundy pitch here, only the highest quality pitches are included.  All kits are shipped in a sturdy wood box that will also serve you when you ship your finished mirror to a coater.


Before You Order


Before ordering, you should familiarize yourself with the various issues and dilemmas associated with observational astronomy and telescope construction.   Visit the following pages and consider the advice.