Amateur Telescope Making in the Internet Age : Finding Parts, Getting Help, and More
In short, the practice was served reasonably well. Last I checked, WIllmann-Bell was the only supplier of mirror blanks and their choices are almost nil. Where might I get a maksutov corrector blank today? Coulter was pushing their Dobson, but they sold glass. Jaegers was pushing value added glass, but you could get raw glass if you asked politely. Willmann-Bell had a much larger selection, including if I recall at some point correctly, a few different Maksutov corrector blanks in the rough.
I sat glued to studying construction articles by author after author, month after month. And then I sat down and set up testing facilities including the simple Foucault test and Ronchi method using gratings.
Used to be, plenty of businesses serving that area. No longer. If the surface is paraboloidal, the mirror looks like a doughnut or lozenge. It is possible to calculate how closely the mirror surface resembles a perfect paraboloid by placing a special mask over the mirror and taking a series of measurements with the tester. This data is then reduced and graphed against an ideal parabolic curve. Some amateur telescope makers use a similar test called a Ronchi test that replaces the knife edge with a grating comprising several fine parallel wires or an etching on a glass plate.
Once the mirror surface has the correct shape a very thin coating of a highly reflective material is added to the front surface. Historically this coating was silver.
Silvering was put on the mirror chemically, typically by the mirror maker or user. Silver coatings have higher reflectivity than aluminum but corrode quickly and need replacing after a few months. Since the s most mirror makers have an aluminum coating applied by a thin-film deposition process work that has to be done by a firm specializing in the process. Modern coatings usually consist of an aluminum layer overcoated with protective transparent compounds. The mirror is aluminized by placing it in a vacuum chamber with electrically heated tungsten or nichrome coils that can evaporate aluminum.
Bookstore Amateur Telescope Making Vol 3
When they hit the surface of the mirror, they cool and stick. Some mirror coating shops then evaporate a layer of quartz onto the mirror, whereas others expose it to pure oxygen or air in an oven so that the mirror will form a tough, clear layer of aluminum oxide. The telescopes amateur telescope makers build range from backyard variety to sophisticated instruments that make meaningful contributions to the field of astronomy. Instruments built by amateurs have been employed in planetary study, astrometry , photometry , comet and asteroid discovery to name just a few.
Therefore, the design, size, and construction of the telescopes vary as well. Some amateur telescope makers build instruments that, while looking crude, are wholly suited to the purpose they are designed for.
Since some amateur telescope makers do not have access to high-precision machining equipment, many elegant designs such as the Poncet Platform , Crayford focuser , and the Dobsonian telescope have evolved, which achieve functionality and stability without requiring precision machining.
The difficulty of construction is another factor in an amateur's choice of project. For a given design the difficulty of construction grows roughly as the square [ citation needed ] of the diameter of the objective. Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers make contributions in doing citizen science, such as by monitoring variable stars, double stars sunspots, or occultations of stars by the Moon or asteroids, or by discovering transient astronomical events, such as comets, galactic novae or supernovae in other galaxies.
The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. The earliest known telescope appeared in in the Netherlands when an eyeglass maker named Hans Lippershey tried to obtain a patent on one. Although Lippershey did not receive his patent, news of the new invention soon spread across Europe.
The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In , Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens and by astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces. An optical telescope is a telescope that gathers and focuses light, mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct view, or to make a photograph, or to collect data through electronic image sensors.
A reflecting telescope is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century, by Isaac Newton, as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position.
Since reflecting telescopes use mirrors, the design is sometimes referred to as a "catoptric" telescope. A Dobsonian telescope is an altazimuth-mounted Newtonian telescope design popularized by John Dobson in and credited with vastly increasing the size of telescopes available to amateur astronomers. Dobson's telescopes featured a simplified mechanical design that was easy to manufacture from readily available components to create a large, portable, low-cost telescope.
The design is optimized for observing faint, deep-sky objects such as nebulae and galaxies. This type of observation requires a large objective diameter of relatively short focal length and portability for travel to less light-polluted locations. Stellafane is the name of the clubhouse built by the Springfield Telescope Makers club of Springfield, Vermont in the early s, and has since come to refer to the club's land and buildings on the summit of Breezy Hill.
It also refers to the Stellafane Convention , a gathering of amateur telescope makers and amateur astronomers held every year at that location. The property is a National Historic Landmark. A catadioptric optical system is one where refraction and reflection are combined in an optical system, usually via lenses dioptrics and curved mirrors catoptrics. Catadioptric combinations are used in focusing systems such as searchlights, headlamps, early lighthouse focusing systems, optical telescopes, microscopes, and telephoto lenses.
Other optical systems that use lenses and mirrors are also referred to as "catadioptric" such as surveillance catadioptric sensors. The Maksutov is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope.
The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration. It was patented in by Russian optician Dmitri Dmitrievich Maksutov. Maksutov based his design on the idea behind the Schmidt camera of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror. The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication. Maksutov telescopes have been sold on the amateur market since the s.
The Gregorian telescope is a type of reflecting telescope designed by Scottish mathematician and astronomer James Gregory in the 17th century, and first built in by Robert Hooke. James Gregory was a contemporary of Isaac Newton, both often worked simultaneously on similar projects. Gregory's design was published in and pre-dates the first practical reflecting telescope, the Newtonian telescope, built by Sir Isaac Newton in However, Gregory's design was only a theoretical description and he never actually constructed the telescope.
It was not successfully built until five years after Newton's first reflecting telescope. The Houghton telescope or Lurie—Houghton telescope is a catadioptric telescope.
Amateur telescope making
Houghton's original design was patented in Instead of the fairly hard to make Schimdt and heavy heavy meniscus Maksutov corrector lenses, the corrector for the Houghton is relatively easy to make. It consists of two lenses: a positive and a negative, set at the front of the telescope which fixes the telescope's aperture. All lens and mirror surfaces are spheroidal, which eases construction.
These lenses are relatively thin, though not as thin as the Schmidt corrector. With a good anti-reflective coating, light loss and "ghost" reflections are minimal. Figuring is the process of final polishing of an optical surface to remove imperfections or modify the surface curvature to achieve the shape required for a given application. Optical Mechanics, Inc. OMI was founded in and produces observatory telescopes, Lidar telescopes, optical tube assemblies, telescope mirrors and reflective coatings for mirrors.
OMI mirrors are used by other telescope makers such as Obsession Telescopes. Also taking on custom projects, they produced the inch Dob, a OMI procured the assets of the former optics company Torus Technologies.
OMI has an optics shop where it does work on telescopes. Ingalls between and while he was an associate editor at Scientific American.
The books cover various aspects of telescope construction and observational technique, sometimes at quite an advanced level, but always in a way that is accessible to the intelligent amateur. The caliber of the contributions is uniformly high and the books have remained in constant use by both amateurs and professionals. Robert Edward Cox was an American optical engineer and a popularizer of amateur telescope making. In astronomy, a mirror support cell - more commonly mirror cell - is a component of a reflecting telescope that supports the mirror in place to hold optical alignment, allow collimation adjustment, and protect it from falling out.
The common usage of the word denotes the cell that holds the primary mirror M1 , however technically it could also be used to denote the support assembly for the secondary mirror M2 or other mirrors. It is commonly used by amateur telescope makers for figuring small astronomical mirrors. Its relatively simple, inexpensive apparatus can produce measurements more cost-effectively than most other testing techniques. The Porter Garden Telescope , was an innovative ornamental telescope for the garden designed by Russell W.
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This article is about the hobby. A primary mirror is the principal light-gathering surface of a reflecting telescope.