2 How to Make a Telescope Jean Texereau How to Make a Telescope Jean Texereau FOREWORD to the American Edition. In this book Jean Texereau tells the entirely uninstructed amateur how to make a first-class astronomical telescope from start to finish-from the important concave mirror to the tube and telescope mounting read}' for use on the heavens. It is an especially well organized book which sticks entirely to the sequence of logic. That is, the entire discussion pertaining to each stage of the work is completed before the book proceeds to the next stage, hence you will not get lost on the way. Because some of that discussion contains a little physical optics it may tend to scare the novice away. Yet you don't have to master all these parts before you begin. Instead, set to work on the mirror and then nibble at them between spells of grinding. Because you will then be actually immersed in the interesting work, the important appertaining theoretical side will then seem more to the point. When you have completed your telescope and become familiar with the general literature on telescope making you will be better able to place Jean Texereau's book on the scale of things. It is not a book for the skitterer who is content with a lick and a dab and a promise, but leans in the direction of the steady, painstaking worker who will become what is known in the hobby as an advanced amateur-one who can turn out an essentally perfect mirror. Month by month, as a series of articles on telescope making, now translated in this book, appeared in 1'Astronomie, the monthly magazine of the Astronomical Society of France, it became evident that Jean 7'exereau's approach to the art was noteworthy. When his acquaintance was scraped by mail it proved that as early as 1938 he had begun as an amateur with Ellison's The Amateur's Telescope and the Amateur Telescope Making books. Like many American advanced amateurs he had turned professional without turning his back on the amateurs, and was therefore what Pat Driscoll of Rochester has patly termed as an Download How to Make a Telescope...pdf Read Online How to Make a Telescope...pdf
Amateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional. Amateur telescope makers (sometimes called ATMs) build their instruments for personal enjoyment of a technical challenge, as a way to obtain an inexpensive or personally customized telescope, or as a research tool in the field of astronomy. Amateur telescope makers are usually a sub-group in the field of amateur astronomy.
Texereau How To Make A Telescope Pdf Free
Before the advent of modern mass-produced telescopes, the price of even a modest instrument was often beyond the means of an aspiring amateur astronomer. Building your own was the only economical method to obtain a suitable telescope for observing. Many published works piqued interest in building telescopes, such as the 1920 book The Amateur's Telescope by Irish telescope maker Rev. W. F. A. Ellison.
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. The mirrors start as a flat disk of glass, typically plate glass or borosilicate glass (Pyrex).[4] The disk is carefully ground, polished and figured to an extremely accurate shape, usually a paraboloid. Telescopes with high focal ratios may use spherical mirrors since the difference in the two shapes is insignificant at those ratios. The tools used to achieve this shape can be simple, consisting of a similarly sized glass tool, a series of finer abrasives, and a polishing pitch lap made from a type of tree sap. Through a whole series of random strokes the mirror naturally tends to become spherical in shape. At that point, a variation in polishing strokes is typically used to create and perfect the desired paraboloidal shape.
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. Other tests used include the Gaviola or Caustic test which can measure mirrors of fast f/ratio more accurately, and home-brew Interferometric testing made possible in recent years by affordable lasers, digital cameras (such as webcams), and computers.
Dear Bernard:Here are the titles of some books that you can order through Amazon.com on telescope making. The first book byJean Texereau is the current standard reference book for beginning telescope makers. You can also find a lot ofother book titles on our AstroMax Book Store.Texereau, How to Make a TelescopeThe Dobsonian Telescope : A PracticalManual for Building Large Aperture TelescopesThe complexity of your project will depend on whether you want to grind your own mirror, or just buy a mirror andbuild the mounts. You can also buy telescope kits from Stargazer Steve,in Canada.Galaxy Optics in California sells large telescope mirrors, thatare probably out of the scope of your project.Edmund Scientific Corporation has several good pamphlets on telescopesand telescope making. These books are a bit out of date, but the basic information is good. They may also sellsmaller mirrors.Don't forget to get the Boy Scout's booklet for the Astronomy Merit Badge!Ed Flaspoehler, Vice PresidentAmerican Association of Amateur AstronomersBack to Top 2. Astronomy Clubs and SocietiesSubj: Astronomy Clubs and SocietiesDate: 5/18/99 11:43:03 PM Central Daylight TimeFrom: redfern@jobseast.asn.au (David Redfern)Sender: redfern@jobseast.asn.au (David Redfern)To: eflaspo@aol.com
The Schiefspiegler (lit. oblique mirror in German), also called tilted-component telescopes (TCT) and off-axis reflecting telescopes, are a type of reflecting telescope featuring an off-axis secondary mirror, and therefore an obstruction-free light path. This is accomplished by tilting the primary mirror so that the secondary mirror does not block incoming light.[1] William Herschel was one of the first to have tilted the mirror of his telescope in order to avoid light loss due to the low reflectivity of his speculum-metal mirror.[2]
When people ask, "How do you make a telescope mirror?" my answer is usually, "You take two circles of glass and rub them together for a long time with sandpaper grit in between." That is what you will be doing. For a while. When the tool is on top (usually abbreviated TOT), the curve in the mirror becomes deeper. When the mirror is on top (MOT), the curve becomes shallower. Take your roughest grit, typically #60 or #80, and put a spoonful on the mirror, which will be on the bottom for the first part. Add some water, use a spray bottle or a squirt bottle. ALWAYS WORK WET - if you don't add water, you can make a bunch of silica dust from the mirror which is terrible for your lungs and health.
You should do a number of wets and start to see the surface of the mirror get kind of frosty from the sanding you are doing. Once it frosts all the way to the edge, take a quick measurement of your sagitta. There are a number of ways to do this. When I made my first mirror I had little money and access to tools. You can buy a feeler gauge set, which is just a bunch of strips of metal of predetermined and indicated thickness. Or you can make or buy a spherometer, a tool that measures the sagitta with high precision with a dial gauge - for a telescope I'm making now, I 3D printed this one.
Once you have finished with a grit, clean, clean, clean everything. Take a toothbrush and soap and water, remove your cleats and throw out the cardboard/newspaper, and make sure that Every. Single. Piece. of old grit is washed off the mirror, work surface, etc. Get it out of the screw heads for your cleats, wash the bucket super well, etc. Honestly, this is the most frustrating and annoying part of making a telescope - you have to clean everything very, very well between grits so that a grain of larger grit isn't between your mirror and tool when you are working with a finer one to scratch the mirror. I found that I would spend as much time cleaning up after a grit size as grinding with it, but it's important so take care with it!
Once your pitch is nice and gooey, take your mirror and coat it with your polishing compound and water (usually cerium oxide). Don't coat the tool - in fact, take some alcohol or acetone or turpentine and wipe the surface off - we want the pitch to stick to it very well, finger oils can prevent that. Then, take your pitch and pour it slowly in a circle on your tool, working towards the center. We want to work while this is all warm so you have to work somewhat quickly here. Then, take your mirror and put it on top of your tool and squish it down a bit. You'll want to end up with a layer of pitch that's about 1/8" thick. Funny story here: I was doing this with the guidance of my good friend who's a telescope maker, I was being a little to cautious here squishing them together. He told me to stand back and then just STEPPED on my mirror and tool. And it worked great. It's good to have friends you can trust!
You'll need to test your mirror to see how spherical it is and if there are any issues, then polish it to a parabola. Stellafane has good resources on navigating this - it's a tricky thing to do but if you keep a log (recommended) of the process, you can get to a good result. I had help from a seasoned telescope maker, and am grateful for that. It takes patience and perseverance, but if you've come this far through this Instructable you have what it takes to finish it off!
Right? The first person I met that had made his own telescope (similar in design to mine, actually) I was like, "Wait, you can grind your own mirror? Tell me more!". I like the reflecting telescope with a shaving mirror - kudos for making a reflector! I've messed around with a few designs for kids to make them, finally settled on a refractor that uses cheap magnifying glasses, some surplus optics lenses and a 3D printed cowling to fit cardboard tubes (one of which is a toilet paper tube). See here: -Paper-Tube-Te... 2ff7e9595c
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