The condensed process of making a tile tool that will be used to grind my 8.5 inch telpe mirror. Making a mould around the Pyrex disc, mixing and pouring...
Why would grind a mirror when you can buy one just as cheaply? When the North American amateur telpe making movement began in the 1920's, there were few alternatives - the only commercial telpes where extremely expensive and often where individually commissioned. Making your own was the only way for most people.
Read Jean Texereau, How to Make a Telpe, even if you do find a good mentor to work with. It's a classic, very well written and the methods he describes are still spot on, in year 2020. I would recommend NOT starting with a thin mirror, a really big mirror, or a really fast mirror. An 8 inch f/6 or even 6 inch f/8 is a great starting point.
Answer (1 of 5): A good friend of mine, and a member of our astronomy club, has ground and polished TWO 32″ diameter mirrors! Yikes! The first one he made was damaged by the coating company, and so he set about making a second mirror! I have looked through both of them, and the images are just st...
This page describes the rough grinding process. Before You Start. Use this checklist to make sure you are ready to start rough grinding: You have selected a mirror diameter and focal ratio, and have use these to calculate a target sagitta.; You have a way to measure sagitta.; You have an appropriate size mirror blank, you have selected a surface to grind, and you have beveled …
Pounding, scraping, knapping, grinding combined with fire, heat, melting leads us today to grinding telpe mirrors from glass. Making a telpe mirror is one of the most satisfying and sublime joys you will experience. It's also arguably the most accurate surface made by man or machine. If the mirror is expanded to the size of a football ...
It is a fine-looking, near full-thickness, 10 inch diameter blank that I intend to grind and polish into a 1st class telpe mirror. Here is a stack of my home-made 8 and 10 inch mirror blanks. The second from the bottom is the one above. I can use the thinner blank below it …
Preparing the Mirror Surface. Four stages of preparation are required before beginning to shape the mirror into a paraboloid. The purpose of the preparation is to make the surface of the mirror progressively smoother. Telpe mirrors have the smoothest surfaces ever made. The highest "peaks" and lowest "valleys" on the mirror surface must be ...
Mirror-O-Matic grinding machine. When I decided in 2009 after a ten-year 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.
Telpe mirrors are relatively thick. The concave shaped face is made by repeatedly rubbing the primary glass blank over another blank called the "tool". The tool is equal in diameter to the primary. To grind away the ... After fine grinding is complete, the mirror must be polished. It is
It probably took me 80-100 hours to simply grind the telpe mirror, but I was learning a lot and taking my time with the process. How are telpe mirrors ground? The primary mirror of most contemporary telpes is made of a solid glass cylinder whose front surface has been honed to a spherical or parabolic form, as seen in the illustration.
Nov 22, 2015 - Gordon started with a 2" thick telpe mirror that weighed about 70 pounds. By thinning the blank, he's lightened the mirror by about 20 pounds! This vid...
For large thin mirrors, say 12 inches [30cm] or greater and 1.5 inches [4cm] or thinner, the mirror back must be ground flat, or at least regular in shape before beginning fine grinding the mirror's face. Cast a tool specifically for the mirror's back, and grind with 220 grit, inspecting for low unground spots. Grind until they disappear.
Page 1 of 2 - Grind mirror blank flat on back - posted in ATM, Optics and DIY Forum: Im getting ready to start grinding my plate glass mirror blank. I"ve been reading and reading on procedures. A few times now Ive come across the comment to make sure to grind the back of the blank flat before starting to grind the curve in the front. One person said to grind it …
Thin Telpe Mirrors . Part 2 - Polishing . Abridged from an article appearing in Telpe Making #13 Provided: Courtesy of Astronomy Magazine Article's Author: Bob Kestner . I am going to start with some additions to topics covered in part 1, on grinding mirrors.
Share. Posted August 24, 2012. The natural mirror grinding process will create a sphere. The first part of making a mirror is to grind and polish to a sphere of the required focal length. Then the mirror is parabolised, by using special polishing strokes, that changes the figure from sphere to paraboloid.
The Stellafane Convention is a gathering of amateur telpe makers. The Convention was started in 1926 to give amateur telpe makers an opportunity to gather to show off their creations and teach each other telpe making and mirror-grinding techniques. All telpes, commercial and homemade, are welcome.
Gordon Waite shows some steps during fine grinding of the 20" mirror. As the grind progresses through the grades of abrasives, see the technique Gordon uses...
To Grind a Telpe Mirror (Three evenings) Authors; Authors and affiliations; M. G. J. Minnaert; Chapter. 134 Downloads; Abstract. This exercise is not intended to make a perfect piece of optics, but just to show the principle of the methods used in practice and to convince our students that amateur telpe making is surprisingly simple and ...
Just input the Sagitta (depth of curve) and Mirror Diameter, and this page will calculate the Focal Length, Focal Ratio and Radius of Curvature. If you want to calculate many other telpe and mirror parameters, use our Telpe Formulas and Design Comparator page.
Rough Grinding The first milestone is putting a curve into the mirror face. The curve's depth dictates the mirror's focal length. The curve should be spherical. Creating the curve can be done by several methods: The curve is ground into the mirror face using a grinding tool. The curve is pre-generated for you.
Grinding an 8″ F/10 Telpe Mirror. For this project (my first time ever grinding a mirror) I ordered an 8″ Black Vitrified Ceramic (BVC) blank without a pregenerated curve from ASM Products in Ste-Basile PQ. Ordering from Canada is always cheaper once you factor in all the taxes – all told the kit cost about $185.
How to grind a mirror blank into the well-figured basis for a Dobsonian telpe. How to grind the glass, how to carry out a focus test, how to polish with ...
It probably took me 80-100 hours to simply grind the telpe mirror, but I was learning a lot and taking my time with the process. A 6″ or 8″ mirror should take between 40 and 80 hours of work to complete. Despite the fact that this is a significant period of time, the mirror may be completed in a few months, and most likely within a year.
It probably took me 80-100 hours to simply grind the telpe mirror, but I was learning a lot and taking my time with the process. How do you polish a telpe? Place the mirror face-up on a towel and, with the drain open, spray the mirror's surface with room-temperature water for a few minutes to remove any lingering residue.
Welcome to my channel - in this video, we will begin to make a telpe mirror from scratch! I'll be showing you the basics of telpe mirror grinding!Her...
Add the usual half teaspoon of grit, sprinkle with water and grind for a couple of minutes, rotating tool and mirror often. Rinse the mirror and inspect the grid lines. If the grid is worn out evenly, you are doing fine. If you grinded with TOT, the edges will be more worn than the center, and vice versa if MOT. This is okay.
I made my first mirror when I was 14, a 6" f/9 (it was supposed to be an f/8, but I had trouble getting the curve deep enough), by myself using Thompson's Making Your Own Telpe. It probably came out no better than 1/2 wave - I don't know - I really didn't know how to test well yet.
Grinding down a telpe mirror can be a lot of work but if you follow these steps you will be able to get it exactly sa you like. Please be careful and use at your own risk None of the authors, contributors, administrators, or anyone else connected with StarryNova, in any way whatsoever, can be responsible for your use of the information ...
The theory behind grinding is that you can remove glass as long as you use a material with a higher hardness. Telpe makers use silicon carbide powders (a.k.a. carborundum) for this task. It is cheap and comes in various size (can range from #36 to #500).
Gordon will know more about the math for different mirrors and different sizes. I recall for mine it was about a 70% tool diameter. The bucket Gordon used to make the tile tool was 8 15/16", 70% of 12.5" ends up at 8 3/4". Looking back at my notes I used the tile tool primarily at the 70% zone of the mirror.
Thin Telpe Mirrors . Abridged from an article appearing in Telpe Making #12 Provided: Courtesy of Astronomy Magazine Article's Author: Bob Kestner . Part I - Grinding . For many years, amateur astronomers and telpe makers thought it essential that glass for telpe primary mirrors be at least one-sixth as thick as its diameter.
Grinding an 8″ F/10 Telpe Mirror. For this project (my first time ever grinding a mirror) I ordered an 8″ Black Vitrified Ceramic (BVC) blank without a pregenerated curve from ASM Products in Ste-Basile PQ. Ordering from Canada is always cheaper once you factor in all the taxes – all told the kit cost about $185. ...
How long to grind and polish a 12 mirror ? - posted in ATM, Optics and DIY Forum: Hello everyone ....I have a 12 precurved mirror blank. Its an f/5 made of 1.25 thick plate glass. I also have a matching dental plaster tool with tiles on it. The tool is a bit thick and weighs close to 5 lbs. Its a subdiameter tool thats almost 10 inches in diameter.
Start with one of our telpe mirror kits. Each kit comes with a telpe 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. Please note that our kits do not include a grinding tool or pitch lap.
It probably took me 80-100 hours to simply grind the telpe mirror, but I was learning a lot and taking my time with the process. How do you silver a telpe mirror? Refining the Reflective Surface. Remove the mirror dam from the mirror and discard the distilled water. The primary solution should be applied to the mirror's surface.
Page 1 of 2 - Grinding your own mirror - How is it possible to get accuracy in the nm? - posted in ATM, Optics and DIY Forum: So I have read forum questions & answers on topics such as whether it is possible to use a 3D printer to design and print out a telpe mirror, or design an array of paraboloids this way for a segmented design, and the answers have been, …
The first thing I built was an extension that sits in the middle of the turntable to raise the working surface above the height of the dam. It was made from an 18 inch diameter tabletop and some scrap lumber. I drew concentric circles on the top of the tabletop in the sizes of common telpe mirror blank diameters.
It would be best if you began by sprinkling the abrasive on the mirror face to make it wet. Avoid being too abrasive. Then place your tool down with the edge first and start grinding. Ensure you are rotating the device by walking around the barrel.
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