Fast mirror grinding and polishing the atms workshop. Waite research is building renegade telescopes with premium primary mirrors 10 and up. Mirror grinding machine posted in atm, optics and diy forum. United lens company supports both the professional and amateur astronomical community. I have plans for the mir o matic but would like to do something a bit more modern. Technicians spend hours and hours of precise and painstaking work grinding and polishing the mirrors to achieve the concave curve that they need. Some coatings last only a few years, while others will. There are many reasons for grinding your own mirror. Mar 04, 2011 basically there are two types of grindingpolishing machine. Grinding high accuracy surfaces with low subsurface damage reduces subsequent polishing time. 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.
Weve sold classic test plate and mirror blanks for nearly as long as ulc has been in business. Throughout the grinding and final lapping stages, the objective has been to reduce pits and scratches to the smallest possible size. This step is about making one side of the glass concave. Part two of my description of the essential steps in making a telescope 2. Executive overview space exploration has had some serious setbacks. 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. If you would like to grind your own telescope mirror, or build a telescope the dobson way, these notes should be very useful. Making a telescope mirror is one of the most satisfying and sublime joys you will experience. Could somebody please point me to a source where i can purchase a kit for grinding a 6 mirror for a newtonian type telescope.
The center will deepen during the first stage of fine grinding as contact is achieved across the mirror face and fine grinding tool. Pounding, scraping, knapping, grinding combined with fire, heat, melting leads us today to grinding telescope mirrors from glass. Some of these techniques have been devised for the specific purpose of making the mirror grinding and polishing operations easier or faster. The grinding machine had been built to the design of the mirror omatic design of dennis rech.
Telescope mirrors, blanks, secondaries, grinding materials. This is part 2 of my video series documenting grinding and polishing a inch telescope mirror. This telescope had two alternative mirrors weighting over a ton. There are five steps in the making the primary mirror. It used the working principle of the machine illustrated at a fig.
How to build a telescope go here for squirrelmail indian institute. Sep 07, 20 this one was right after i finished the fixed post grinder. Generations of amateur telescope makers have been taught to proceed by. The center will deepen during the first stage of fine grinding as contact is achieved across. Mirrors are much cheaper, per unit area, than detectors. 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. Additionally, we provide highend custom solutions including the application of durable thin film mirror and antireflective coatings. Telescope mirror blanks providing telescope mirror blanks and kits to telescope makers. 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.
Telescope mirrors, blanks, secondaries, grinding materials, testers, aluminising, making advice. All mirrors are made inhouse on our commercial fabrication equipment no home built rickety machines. 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. When you first start a new and smaller abrasive, this shows up as a tendency to form a large bubble in the center. 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. Mirror grinding machine construction log i started thinking about building my own mirror grinding machine several years ago. Zambuto optical company is a full service custom manufacturer of premium newtonian primary telescope mirrors from 7 through 24 diameter. I used a chisel and a belt sander to put a curve on the. He loves anything having to do with science or bicycling. King telescopes, telescope mirror blanks, using both quartz. 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.
We do this to insure that every obsession telescope customer receives the finest optics and customer support available. Practical calculations for designing a newtonian telescope. Gordon started with a 2 thick telescope mirror that weighed about 70 pounds. Another work in progress although its complete enough to make a mirror at this time. Im thinking of making my own fixed post mirror grindingpolishing and curve generating machine. Optic wave laboratories offers a standard line of parabolic or newtonian telescope mirrors. 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. Such glass is usually used for tabletops and window displays. Grinding metrescale mirror segments for the eelt ground. 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. For looseabrasive grinding and polishing we use the same stressed lap.
The quality of reflector telescopes depends a lot on the perfection of the mirror surface. One of the most expensive mirror makers around is r. One of the most often mentioned is the hubble space telescope. 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. From diamond curve generation, grinding, polishing, figuring, testing and coatings we control the entire process. Making my own fixed post mirror grindingpolishing machine. Our i nnovative telescope design and optics offer exquisite night views of saturn, jupiter, and. A solid tool traps abrasive in the center of the mirror and resists grinding the mirror spherical.
Telescope mirrors, blanks, secondaries, grinding materials, testers, aluminising, making advice information. I read several telescope and mirror making books and visited many amateur telescope making or atm websites to learn how to build a 14. Dennis rechs mom designs finally inspired me to just get up and do it. Mirror blank kit posted in atm, optics and diy forum. Dec 16, 2014 gordon started with a 2 thick telescope mirror that weighed about 70 pounds. Hogging out means making your mirror blank have roughly the proper concave shape for the focal length or fratio that you want. 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. Small mirrors are generally ground and polished by rotating the tool, fastened to the turntable, and working the mirror blank by hand. In conventional telescope mirror grinding standards it is required to maintain thickness to diameter. Welcome to king telescopes not an impressive website. The lens at the other end of the telescope is called the objective lens. Further technical details may be found in many books on amateur telescope making.
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. Introduction mirror or lens grinding by hand can be a labour of love. By thinning the blank, hes lightened the mirror by about 20 pounds. 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. The machine can also work smaller mirrors if the drip pan is moved to the fast shaft on the side of the machine. By slipping on and off a couple of belts, the machine can quickly be reconfigured for spinning work or for stroking work. Mirroromatic mirror making machine atm pages of berthold. Heres another way to do the work along with some digressions on doing things related to making mirrors. More importantly, the glass tool can be saved and used later as a mirror blank for a second project. At present we have a supply of high quality pyrex mirror blanks. The optical characteristics of a telescope diameter and focal length should. Fabrication of large secondary mirrors for astronomical telescopes bryan k.
Constructing grinding and polishing machines nasaads. Grinding a telescope reflector with toolgrinding device by george f. Therefore, we take a mechanical measurement of the sagitta, or depth of curve, and using some simple formulas calculate the focal length. I can at least understand the process of grinding or lapping a surface flat. George willis ritchey built this mirror grinding machine at the yerkes observatory in williams bay, wisconsin, in the late 1890s. Here is a 25 inch 635cm mirror being rough ground followed by a beautiful grinding stand from the delmarva mirror making seminar. The casting process leaves the blanks slightly oversize, and the edges of the blanks rough, and not quite perfectly round. There are many articles and web pages on this, which you really should look at. 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. I designed and built a grinding machine for mirrors up to 42 inches 1. Renegade telescopes now available with 10 to 27 primary mirrors. These mirrors or any telescope we may supply with these mirrors is not supplied with a full zygo report.
How i built an edge grinder for telescope mirror blanks. 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. For a long time ive wanted to build a machine for grinding telescope mirrors. I have read that telescope mirrors require periodic realuminizing. Find telescope mirror grinding tools related suppliers, manufacturers, products and specifications on globalspec a trusted source of telescope mirror grinding tools information. I have been casting my own telescope mirror blanks for a few years now. How i do it is explained elsewhere on this web site. For these mirrors, as you near the depth, you can alter the strokes to be offcenter. Making a reflector telescope a quick word about mirrors. 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. Glass tools can stick and cause scratches in larger sizes.
Its also arguably the most accurate surface made by man or machine. You might purchase a mirror grinding kit, and have everything you need included. King telescopes, telescope mirror blanks, using both. Page 1 of 2 making my own fixed post mirror grindingpolishing machine posted in atm, optics and diy forum. Precision grinding for rapid fabrication of segments for. If you make the centre deep, you will end up with a fast telescope e. Tauchmann grinding telescope reflectors of 15inch diameter and over makes it necessary to employ a motordriven turntable. 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. 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. Thin plate glass mirror blanks are lighter than standard mirror blanks, which allows you more flexibility in designing your telescope tube assembly and mount. I have tried various methods of cleaning up the edges of the blanks. Telescope tube, mirror cell, diagonal and eyepiece. Mirror blanks are individually tested for internal strain. These notes were taken during john dobsons telescope making class in san francisco, fall 1996.
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. Nov 15, 2001 there are numerous techniques that have been described over the years for grinding and polishing mirrors. 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. You can order a 19 mm thick disc at your local glass shop. Page 1 of 2 grinding your own mirror how is it possible to get accuracy in the nm.
Pdf study of thin telescopic mirror fabrication and mirror cell. I have some ideas about using a ac drive and a large aluminum disk for the turntable and have made a parts list for. Henry draper 18371882 started by grinding metal mirrors but soon changed to silvercoated glass mirrors. How to grind a mirror blank into the wellfigured basis for a dobsonian telescope. Over the years, id been collecting motors, gear boxes, pulleys, etc. 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. Pdf techniques of eighteenth century telescope makers, pt. I have tried out many of these ideas and techniques at one time or another. Martin university of arizona, steward observatory mirror lab 527 n. 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. The table below can be used as a rough guide in obtaining the grit, polish and pitch necessary for a small mirror project. The distribution between less and more is spherical. Under the sponsorship of george ellery hale, the machine was used to grind a series of telescope mirrors starting with a 24inch and then a 60inch mirror for a telescope initially intended for the yerkes observatory.
Buy telescope mirror grinding and testing on free shipping on qualified orders. Fixed post mirror grinding table designed with 123d design. This efficient grinding process provides the capacity to grind 1. Mirror blank kit atm, optics and diy forum cloudy nights. How do you turn a chunk of glass into a telescope mirror, with a surface accurate to a. Telescope mirror making frontier homepage powered by yahoo. Our intent is to provide a source for lower cost, mirror blanks, and supplies for grinding your own telescope mirror.
During mirror making, a very high strehl measurement can be case of luck. 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. How will you know when you telescope mirrors need re. Mirror grinding machine construction log james crombie. Grinding and polishing the mirror is the most difficult part of making a telescope. Fabrication of large secondary mirrors for astronomical. 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. 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. If such a kit is unavailable, you need to do some scrounging.
Measuring sagitta depth of curve during grinding, the mirror is too rough to measure the focal length optically to any reasonable precision. Royce does not let his mirrors out unless they have a strehl of at least 96%. Testing and correcting the mirror until the sweet spot is achieved. Zambuto optical company newtonian telescope mirrors. I made my first mirror grinding and polishing machine over thirty years ago. Either you want a unusual size, or focal length, or to satisfy your. 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. 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. Ritchey mirror grinding machine national air and space. Fd 8 will be performing very well on planets and the moon.
Grinding metre scale mirror segments for the eelt ground. 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. One must have optics made from precision pyrex or a similar material. How do you turn a chunk of glass into a telescope mirror. This web page provides an overview of my large homemade telescope making project.
After hogging the mirror blank to depth, the rough grinding stage begins. I have some interest in building a grinding machine for possible up to an 18 mirror, but something that will also do a 6 or 8 mirror. 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. On larger mirrors, the ring tool may leave the zones part way to the edge a little underground. 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. 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. Pyrex is commonly used for the primary mirror because of its thermal stability, but for small mirrors, plate glass will work fine too.
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