Making a reflector telescope a quick word about mirrors. I have plans for the mir o matic but would like to do something a bit more modern. This efficient grinding process provides the capacity to grind 1. Making my own fixed post mirror grindingpolishing machine. Mirror blank kit atm, optics and diy forum cloudy nights. Find telescope mirror grinding tools related suppliers, manufacturers, products and specifications on globalspec a trusted source of telescope mirror grinding tools information. Fabrication of large secondary mirrors for astronomical. Request pdf grinding metre scale mirror segments for the eelt ground based telescope the next generation of ground based telescopes require many hundreds of metre scale offaxis mirrors. If you would like to grind your own telescope mirror, or build a telescope the dobson way, these notes should be very useful. You might purchase a mirror grinding kit, and have everything you need included. Dec 16, 2014 gordon started with a 2 thick telescope mirror that weighed about 70 pounds. Small mirrors are generally ground and polished by rotating the tool, fastened to the turntable, and working the mirror blank by hand. I have been casting my own telescope mirror blanks for a few years now.
More importantly, the glass tool can be saved and used later as a mirror blank for a second project. Mar 04, 2011 basically there are two types of grindingpolishing machine. How to grind the glass, how to carry out a focus test, how to polish with a pitch lap and how to find the focal. Hogging out means making your mirror blank have roughly the proper concave shape for the focal length or fratio that you want.
In conventional telescope mirror grinding standards it is required to maintain thickness to diameter. Obsession telescopes chooses to work with optical mechanics and ostahowski optics as these two companies have proven to be reliable and responsive to the needs of our customers. Fast mirror grinding and polishing the atms workshop. By slipping on and off a couple of belts, the machine can quickly be reconfigured for spinning work or for stroking work. On larger mirrors, the ring tool may leave the zones part way to the edge a little underground. The machine can also work smaller mirrors if the drip pan is moved to the fast shaft on the side of the machine.
Having been on the atm list now since almost the beginning of it here on the web, i had lots of of inspiration reading of others projects and viewing their webpages. Technicians spend hours and hours of precise and painstaking work grinding and polishing the mirrors to achieve the concave curve that they need. Weve sold classic test plate and mirror blanks for nearly as long as ulc has been in business. Here is a 25 inch 635cm mirror being rough ground followed by a beautiful grinding stand from the delmarva mirror making seminar.
Ritchey mirror grinding machine national air and space. Could somebody please point me to a source where i can purchase a kit for grinding a 6 mirror for a newtonian type telescope. When you first start a new and smaller abrasive, this shows up as a tendency to form a large bubble in the center. If you make the centre deep, you will end up with a fast telescope e. Fd 8 will be performing very well on planets and the moon. From diamond curve generation, grinding, polishing, figuring, testing and coatings we control the entire process. Telescope mirrors, blanks, secondaries, grinding materials, testers, aluminising, making advice information. However, no amount of grinding can produce a surface smooth enough or sufficiently transparent to meet the needs of a firstclass telescope objective. Some coatings last only a few years, while others will. I have some ideas about using a ac drive and a large aluminum disk for the turntable and have made a parts list for. Glass tools can stick and cause scratches in larger sizes.
Grinding and polishing the mirror is the most difficult part of making a telescope. If i had known as a kid how, well not easy, but indeed not as hard as i would have expected to grind my own mirror. Another work in progress although its complete enough to make a mirror at this time. Page 1 of 2 grinding your own mirror how is it possible to get accuracy in the nm. Mar 10, 2017 the center of the mirror is the most likely to be contacted by any motion, so it is abraded more frequently and becomes the deepest point, while the edges are worn less.
This web page provides an overview of my large homemade telescope making project. Plastic protractor inserted under a 6 inch mirror blank during a stress test, to illustrate what stress would look like if there were any present. During mirror making, a very high strehl measurement can be case of luck. When you first start a new and smaller abrasive, this shows up as a tendency to form a large bubble in the center, especially in the larger abrasives. Page 1 of 2 making my own fixed post mirror grindingpolishing machine posted in atm, optics and diy forum. George willis ritchey built this mirror grinding machine at the yerkes observatory in williams bay, wisconsin, in the late 1890s. How i do it is explained elsewhere on this web site. Mirror grinding machine atm, optics and diy forum cloudy. Additionally, we provide highend custom solutions including the application of durable thin film mirror and antireflective coatings. When i decided in 2009 after a tenyear break to get into mirror making again, it quickly became clear to me that i would need to construct machine, as hand grinding big mirrors is not something very beneficial for the hands of a musician. Shipping prices are to the usa not shipping outside the us, sorry combined shipping is possible write for a complete mirror making kit, with all abrasives, polishing compounds, pitch, and grinding tool included, please see our buy telescope mirror kits. There are many articles and web pages on this, which you really should look at. The majority of these primaries we make are bought by amateur telescope makers or just customers who want to upgrade the optics in their imported, usually chinese branded telescope. One must have optics made from precision pyrex or a similar material.
Generations of amateur telescope makers have been taught to proceed by. Mirror grinding machine construction log i started thinking about building my own mirror grinding machine several years ago. Measuring sagitta depth of curve during grinding, the mirror is too rough to measure the focal length optically to any reasonable precision. Telescope mirror making frontier homepage powered by yahoo. I designed and built a grinding machine for mirrors up to 42 inches 1.
How do you turn a chunk of glass into a telescope mirror, with a surface accurate to a. Executive overview space exploration has had some serious setbacks. The center will deepen during the first stage of fine grinding as contact is achieved across the mirror face and fine grinding tool. Our i nnovative telescope design and optics offer exquisite night views of saturn, jupiter, and. I can at least understand the process of grinding or lapping a surface flat. Precision grinding for rapid fabrication of segments for. Constructing grinding and polishing machines nasaads. Royce does not let his mirrors out unless they have a strehl of at least 96%.
Mirror grinding machine posted in atm, optics and diy forum. I read several telescope and mirror making books and visited many amateur telescope making or atm websites to learn how to build a 14. The grinding machine had been built to the design of the mirror omatic design of dennis rech. Mirroromatic mirror making machine atm pages of berthold. Welcome to king telescopes not an impressive website. You can order a 19 mm thick disc at your local glass shop. Tauchmann grinding telescope reflectors of 15inch diameter and over makes it necessary to employ a motordriven turntable. There are a lot of misconceptions about making a mirror read this even if you dont plan to make a mirror, but just want to know how it is done with your bare hands and a few simple tools, you can grind and figure a fine mirror with a surface accurate to a few millionths of an inch. How will you know when you telescope mirrors need re. Grinding a telescope reflector with toolgrinding device by george f. For looseabrasive grinding and polishing we use the same stressed lap.
This telescope had two alternative mirrors weighting over a ton. One of the most expensive mirror makers around is r. Telescope mirrors, blanks, secondaries, grinding materials. The casting process leaves the blanks slightly oversize, and the edges of the blanks rough, and not quite perfectly round. At present we have a supply of high quality pyrex mirror blanks. Optical telescope integration and test ittexelis mirror manufacturing beryllium mirror blanks brush wellman mirror machining axsys technologies mirror grinding and polishing ssgtinsley laboratories webb telescope operating in space nearly a million miles from earth and protected by its tennis courtsized, fivelayer sunshield, the webb. Either you want a unusual size, or focal length, or to satisfy your. If such a kit is unavailable, you need to do some scrounging.
This step is about making one side of the glass concave. The traditional type which involves the mirror rotating at a relatively slow speed, a few rpm for a big mirror 1620 inches with the tool moving across the mirror, from side to side, at a higher rpm depending on the size of the mirror andor tool. There are five steps in the making the primary mirror. The quality of reflector telescopes depends a lot on the perfection of the mirror surface. Each kit comes with a telescope mirror blank and all the abrasives silicon carbide grits and white aluminum oxide powders, cerium oxide polish and pitch to grind and polish it to your specifications. I made my first mirror grinding and polishing machine over thirty years ago. How i built an edge grinder for telescope mirror blanks. Fixed post mirror grinding table designed with 123d design. Please make use of this fill out form to report any problem urls or suggest new ones amateur telescope making atm links these links were collected mainly from postings to the atm mailing list. Grinding metrescale mirror segments for the eelt ground.
Searchable archives of this list is here and a number of astronomy related mailing lists here be sure to also visit my astronomy links page. Grinding high accuracy surfaces with low subsurface damage reduces subsequent polishing time. How to build a telescope go here for squirrelmail indian institute. Further technical details may be found in many books on amateur telescope making.
Over the years, id been collecting motors, gear boxes, pulleys, etc. A solid tool traps abrasive in the center of the mirror and resists grinding the mirror spherical. Part two of my description of the essential steps in making a telescope 2. Fabrication of large secondary mirrors for astronomical telescopes bryan k. Practical calculations for designing a newtonian telescope. How do you turn a chunk of glass into a telescope mirror. Telescope tube, mirror cell, diagonal and eyepiece. Martin university of arizona, steward observatory mirror lab 527 n. Grinding metre scale mirror segments for the eelt ground. Im thinking of making my own fixed post mirror grindingpolishing and curve generating machine. Zambuto optical company newtonian telescope mirrors. Mirror blanks are individually tested for internal strain. These mirrors or any telescope we may supply with these mirrors is not supplied with a full zygo report.
Gordon started with a 2 thick telescope mirror that weighed about 70 pounds. It used the working principle of the machine illustrated at a fig. The center will deepen during the first stage of fine grinding as contact is achieved across. Building a telescope theory a b objective science and mathematics standards materials in a telescope, the lens held next to your eye is called the eyepiece and is usually a short focal length lens or a combination of lenses. Thin plate glass mirror blanks are lighter than standard mirror blanks, which allows you more flexibility in designing your telescope tube assembly and mount. Mirror grinding machine construction log james crombie. Its also arguably the most accurate surface made by man or machine. For grinding the back of my 12 mirror, i used an 8 disk of 34 particle board, glued tiles to the front with epoxy, and coated the back and sides with polyurethane. Testing and correcting the mirror until the sweet spot is achieved. Introduction mirror or lens grinding by hand can be a labour of love.
Renegade telescopes now available with 10 to 27 primary mirrors. King telescopes, telescope mirror blanks, using both quartz. Henry draper 18371882 started by grinding metal mirrors but soon changed to silvercoated glass mirrors. One of the most often mentioned is the hubble space telescope. But has anyone diy grinded an aspherical mirror like one to be used in a multi mirror setup. Engineering, design and construction of portable newtonian telescopes, advanced telescope making techniques volume 1 optics, advanced telescope making techniques volume 2 mechanica, a manual for amateur telescope makers, amateur telescope making, the best of amateur telescope making journal, build your own telescope, the dobsonian telescope, how to make a telescope, introduction. Therefore, we take a mechanical measurement of the sagitta, or depth of curve, and using some simple formulas calculate the focal length. When grinding a telescope mirror, you will find that plate glass takes less time to grind and polish than a mirror made from borosilicate glass. After hogging the mirror blank to depth, the rough grinding stage begins.
I have tried various methods of cleaning up the edges of the blanks. Ive got loads of questions regarding the design so ill just start firing away do i need an eccentric moving tool to be able to polish a mirror spherical. The mirror machine came to me as a result of astronomical horsetrading, swapping a large gem mount and a 8 newtonian ota for the machine as it was and a start kit consisting of two 6 blanks and the grit, rouge and pitch to manufacture a mirror. Dennis rechs mom designs finally inspired me to just get up and do it. So if you want to gather a lot of radiation, it makes sense to build a big mirror to gather all the radiation into a small spot, and put a detector there. I have read that telescope mirrors require periodic realuminizing. Practical calculations for designing a newtonian telescope jeff beish rev. While its true that the aluminized surface of a telescope mirror will deteriorate over time, there is no hard and fast rule about how long this will take. Such glass is usually used for tabletops and window displays. Mirror grinding tutorial how do you turn a chunk of glass into a telescope mirror, with a surface accurate to a couple millionths of a millimeter.
The lens at the other end of the telescope is called the objective lens. For these mirrors, as you near the depth, you can alter the strokes to be offcenter. If one of our standard telescope mirror blanks isnt exactly what youre looking for, advanced glass can custom make a telescope mirror blank to your specifications. By thinning the blank, hes lightened the mirror by about 20 pounds. Pyrex is commonly used for the primary mirror because of its thermal stability, but for small mirrors, plate glass will work fine too. Mirror making is a hobby that has been around for many years, and many people have put their hands to the task, but it is time consuming, requiring a great deal of skill, patience and perseverence. For a long time ive wanted to build a machine for grinding telescope mirrors. Some of these techniques have been devised for the specific purpose of making the mirror grinding and polishing operations easier or faster. Zambuto optical company is a full service custom manufacturer of premium newtonian primary telescope mirrors from 7 through 24 diameter. He loves anything having to do with science or bicycling. Sep 07, 20 this one was right after i finished the fixed post grinder. Be aware that buying small quantities of is often difficult and expensive, and the first time mirror maker usually does best to purchase a mirror making kit which includes the necessary set of abrasives and pitch.
Unfortunately, the cost of mirror grinding kits and pyrex blanks has increased significantly in recent years to the point where any savings from making a mirror versus buying one are minimal at best. Heres another way to do the work along with some digressions on doing things related to making mirrors. Telescope mirrors, blanks, secondaries, grinding materials, testers, aluminising, making advice. Pdf techniques of eighteenth century telescope makers, pt.
King telescopes, telescope mirror blanks, using both. Throughout the grinding and final lapping stages, the objective has been to reduce pits and scratches to the smallest possible size. I used a chisel and a belt sander to put a curve on the. There are many reasons for grinding your own mirror. How to grind a mirror blank into the wellfigured basis for a dobsonian telescope. This is part 2 of my video series documenting grinding and polishing a inch telescope mirror. Nov 15, 2001 there are numerous techniques that have been described over the years for grinding and polishing mirrors. Optic wave laboratories offers a standard line of parabolic or newtonian telescope mirrors. These notes were taken during john dobsons telescope making class in san francisco, fall 1996.
Pdf study of thin telescopic mirror fabrication and mirror cell. Waite research is building renegade telescopes with premium primary mirrors 10 and up. Diy mirror grinding aspherical i understand that people have been able to grind a mirror thats spherical with a very simple grinding disk set on an arm that just moves in a repeating fashion. Making a telescope mirror is one of the most satisfying and sublime joys you will experience. The optical characteristics of a telescope diameter and focal length should. Mirror blank kit posted in atm, optics and diy forum.
Our intent is to provide a source for lower cost, mirror blanks, and supplies for grinding your own telescope mirror. Pounding, scraping, knapping, grinding combined with fire, heat, melting leads us today to grinding telescope mirrors from glass. Telescope mirror blanks providing telescope mirror blanks and kits to telescope makers. All mirrors are made inhouse on our commercial fabrication equipment no home built rickety machines. I have tried out many of these ideas and techniques at one time or another. Mirrors are much cheaper, per unit area, than detectors.
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