Its also arguably the most accurate surface made by man or machine. Making a homemade mirror grinding machine posted in atm, optics and diy forum. Telescope mirror blanks providing telescope mirror blanks and kits to telescope makers. Our intent is to provide a source for lower cost, mirror blanks, and supplies for grinding your own telescope mirror. United lens company supports both the professional and amateur astronomical community. Use a sand mixture and another piece of glass to grind away the middle of a concave shape. Dennis rechs mom designs finally inspired me to just get up and do it. For hand grinding, the coarse grit sequence of 40, 60, 80, 120, 220 is typical start at the grit size appropriate for your mirror diameter as given in the section above. Secondary mirror offset to avoid a loss in optical path at the edge of the secondary mirror that pointed towards the primary mirror, some atm ers find it necessary to mechanically shift the secondary mirror away from the focuser and towards the primary mirror. King telescopes, telescope mirror blanks, using both. I made my polishing tool for my 12 mirror out of three layers of 34 particle board glued together. Ranging in aperture from 6 to 16 and offered in various fratios, these mirrors are made from optical grade bk7 glass.
Grinding a mirror using an abrasive and a smaller tool over 300 mm mirror atm korenica 2006, in korenica, croatia since the newtonian reflector is the most common telescope built by amateur telescope makers, large sections of the literature on the subject are devoted to fabrication of the primary mirror. Making a homemade mirror grinding machine atm, optics and. Jan 18, 2017 the giant magellan telescope will feature seven enormous mirrors and one spare each a precisely engineered piece of glass 27. Most amateur astronomers believe, i can buy a better telescope than i can build. Please email or call for information, pricing confirmations and shipping prices. The strehl ratio compares the mirrors actual performance in terms of its ability to focus light into the diffraction disk, as predicted by interferometry. The mirror is now on the bottom, dont forget to rotate the mirror. All mirrors are made inhouse on our commercial fabrication equipment no home built rickety machines. The mirrors were tested on a distant object and then tried on the.
For these mirrors, as you near the depth, you can alter the strokes to be offcenter. Cutting it into smaller sections can be difficult but scoring it with a glass cutter and tapping t. 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. Simple tools, grinding materials and time allow amateur astronomers to make properly curved astronomical mirrors and to build large reflector telescopes for a fraction of the cost of similarly.
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. 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. May 28, 2016 documenting the telescope build, including mirror grinding and figuring, and construction of the renegade telescope body. Fig 1 this is a large piece of glass a woman off craigslist gave me. Part two of my description of the essential steps in making a telescope 2. Sep 23, 2012 after hogging the mirror blank to depth, the rough grinding stage begins. This will get you on a great start to building your own telescope. A 10inch telescope mirror has a 10inch or 250mm primary mirror. However, the price of the mirror increases as the mirror gets larger. It is cheaper, it is softer and grinds faster, needing less abrasives and with these small sizes, the low expansion glass like pyrex has no practical visible at. Pounding, scraping, knapping, grinding combined with fire, heat, melting leads us today to grinding telescope mirrors from glass. Im thinking of making my own fixed post mirror grindingpolishing and curve generating machine. All about telescopes, by sam brown found at orion telescope and binocular center also has good instructions.
Back in the 60s and 70s i bought most of the sam brown booklets from edmund scientific along with a 6 inch mirror grinding kit. Please see the buy telescope mirror blanks page for low prices on plate glass mirror blanks. At present we have a supply of high quality pyrex mirror blanks. Making a mirror grinding tool by allen malsburry the average person would never think, i can make my own telescope. If you make the centre deep, you will end up with a fast telescope e. Browse an extensive selection of astronomy equipment at telescopes.
Optic wave laboratories offers a standard line of parabolic or newtonian telescope mirrors. Since the mirror is already good to about one half wave we feel that the ronhi test at the center of curvature will only help until the mirror is better than one 14 wave, or so. Agi also supplies schott supremax 33 mirror blanks. A small, flat, frontsurface mirror called the diagonal or secondary mirror is mounted inside the telescope tube near the front end. The center will deepen during the first stage of fine grinding as contact is achieved across. Mirroromatic mirror making machine atm pages of berthold. Welcome to king telescopes not an impressive website. One of the most often mentioned is the hubble space telescope. 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. Much is also unchanged mirror grinding techniques are very similar to those written up by porter and ingalls in the 20. Dave barosso demonstrates the technique, but to do it yourself, try to visit one of the telescope makers workshop s classes on friday nights in oakland. For many decades now, amateur astronomers have been building their own telescopes.
Practical calculations for designing a newtonian telescope. Youall learn the stepbystep method for grinding and polishing the mirror, building the mount, and assembling a complete telescope. We offer a telescope mirror re coating service for both primary and secondary telescope mirrors. How to make your own telescope mirror instructables. For mirrors under 19, i would not use glass under 1 thick. Supremax 33 is a borosilicate pyrex equivalent, and is an excellent alternative for telescope mirror blanks. However, no amount of grinding can produce a surface smooth enough or sufficiently transparent to meet the needs of a firstclass telescope objective. 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. 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. It seems that lap on top polishing with short strokes actually shortens the mirror radius. You will learn about john dobson and his reflector telescope, as well as how these telescopes work. May 30, 2014 this is how you make a telescope mirror out of a hunk of glass. Astronomy clubs many can offer help with your project. How i do it is explained elsewhere on this web site.
All about telescopes how to build how to use mirror. This kit includes an 8 inch telescope mirror blank, all the silicon carbide grits, white aluminum oxide powders, gugolz pitch picture shows 2 lb container, and cerium oxide polish you will need to grind and polish an 8 inch telescope mirror all bundled in one spot. Throughout the grinding and final lapping stages, the objective has been to reduce pits and scratches to the smallest possible size. Johns amateur telescope making page lots of useful atm info, particularly on mirror making and testing for the beginner atm stepbystep mirror making flowchart with links victors home page all the info youll need on grinding your own mirror. Corning no longer produces pyrex for optical use, however advanced glass industries has a limited stock of pyrex in house. The curves depth dictates the mirror s focal length. If the mirror is expanded to the size of a football.
This step is about making one side of the glass concave. It deflects light from the objective to the side of the tube where the image may be more easily examined with an eyepiece. Renegade telescopes include premium, handfigured, waite research mirrors, topend starlight instruments. Primary, secondary, and tertiary mirrors, tools, abrasives and material used from grinding to polishing.
Grinding and polishing the mirror is the most difficult part of making a telescope. Generations of amateur telescope makers have been taught to proceed by. Well, nothing is ever perfect but we plan to polish our 30 year old mirror until the mirror figure is better than can be used under most seeing conditions. Page 1 of 2 making my own fixed post mirror grindingpolishing machine posted in atm, optics and diy forum. I have been casting my own telescope mirror blanks for a few years now. A telescope mirror is designed to form a diffraction limited image of a point source. There are many reasons for grinding your own mirror. Ideally, a certain percentage of the light in the image will fall within the diffraction disk diameter. This is the first mirror of a pair that will become a 22 binocular scope. There are many articles and web pages on this, which you really should look at. Since the original version of this program we have learned a bit more about polishing lap on top. We are your source for astronomy telescopes, eyepieces, astroimaging cameras, and more. Making my own fixed post mirror grindingpolishing machine.
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. Over the years, id been collecting motors, gear boxes, pulleys, etc. Weve sold classic test plate and mirror blanks for nearly as long as ulc has been in business. If youd like to buy a complete mirror grinding kit, with all abrasives and grinding tool included, please see the buy telescope mirror kits. Mirror blanks are individually tested for internal strain. Heady stuff for a 14 year old to take on single handed, but tremendously educational in ways that still help me in my job. Save money and time by purchasing a telescope mirror kit. Henry draper 18371882 started by grinding metal mirrors but soon changed to silvercoated glass mirrors. Gordon started with a 2 thick telescope mirror that weighed about 70 pounds. The strehl ratio compares the mirror s actual performance in terms of its ability to focus light into the diffraction disk, as predicted by interferometry.
They are great for beginning and expert amateur telescope makers. I want to make a motorized mirror grinder, any good info on this, i have a couple geared motors, low speed high torque. Mirrors are much easier to make than lenses and as a result amateur astronomers can build large aperture telescopes after grinding their own mirrors. The drama of that fiasco is a human and organizational tapestry perhaps more complex than the technology involved.
It probably came out no better than 12 wave i dont know i really didnt know how to test well yet. The quality of reflector telescopes depends a lot on the perfection of the mirror surface. Gsos parabolic primary mirrors are perfect for those who want to build their own telescopes or replace mirrors in older ones. From diamond curve generation, grinding, polishing, figuring, testing and coatings we control the entire process.
Also, victors telescope making page has step by step instructions for mirror making. Cox, then coeditor of the gleanings for atms column. For many years, amateur astronomers and telescope makers thought it essential that glass for telescope primary mirrors be at least onesixth as thick as its diameter. On larger mirrors, the ring tool may leave the zones part way to the edge a little underground.
A lot has changed since russell porter wrote those words today the average workman can afford to buy an already made telescope and dobsonian mountings are very popular. Part 1 includes prepping the mirror for grinding, spherometry on the. The large aperture mirror array lama is a novel concept for an extremelylarge telescope. Rough grinding the first milestone is putting a curve into the mirror face. Fd 8 will be performing very well on planets and the moon. If you are interested in grinding and polishing your own mirror, we suggest you pick up john dobsons video listed under sources below as a start. The curve is ground into the mirror face using a grinding tool. Executive overview space exploration has had some serious setbacks. This video shows preparations for grinding a 22 f4.
Hogging out means making your mirror blank have roughly the proper concave shape for the focal length or fratio that you want. 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. The center will deepen during the first stage of fine grinding as contact is achieved across the mirror face and fine grinding tool. Most atm books and websites recommend a pyrex mirror blank, but in my opinion, annealed plate glass is better for this first, learn and practice mirror. The casting process leaves the blanks slightly oversize, and the edges of the blanks rough, and not quite perfectly round. 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. A reflecting telescope also called a reflector is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. King telescopes, telescope mirror blanks, using both quartz. I made my first mirror when i was 14, a 6 f9 it was supposed to be an f8, but i had trouble getting the curve deep enough, by myself using thompsons making your own telescope.
Either you want a unusual size, or focal length, or to satisfy your curiosity, or to have the pride of achievement by fabricating something as precise as a telescope mirror. All mirrors have a reflective aluminum coating with a reflectivity of 9293%. Additionally, we provide highend custom solutions including the application of durable thin film mirror and antireflective coatings. All our mirror kits contain a pilkington float glass mirror blank and grinding tool. Page 1 of 2 grinding your own mirror how is it possible to get accuracy in the nm. Herschel used no scientific approach to test his mirrors. The thickness you choose, if you have a choice, is determined by the diameter of the mirror and how you plan to mount the mirror in the telescope. For a long time ive wanted to build a machine for grinding telescope mirrors. This mirror is mounted at a 45 degree angle to the tubes axis hence its name. Basically there are two types of grinding polishing machine. Mobsby of blandford forum, dorset, england, describing a method of testing medium and long focus mirrors with a special inverse grating that can be interpreted with the ease of a null test.
Technicians spend hours and hours of precise and painstaking work grinding and polishing the mirrors to achieve the concave curve that they need. I have tried various methods of cleaning up the edges of. These mirrors or any telescope we may supply with these mirrors is not supplied with a full zygo report. Professional professional grade optics primaries are produced from quality low expansion suprax glass from schott germany. Our i nnovative telescope design and optics offer exquisite night views of saturn, jupiter, and the moon, as well as open clusters, nebulae and galaxies. Telescope mirrors, blanks, secondaries, grinding materials. Making the giant magellan telescopes massive, incredibly. How i built an edge grinder for telescope mirror blanks. Our blanks have the following standard characteristics. Waite research is building renegade telescopes with premium primary mirrors 10 and up. I have tried various methods of cleaning up the edges of the blanks. 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.
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