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Homemade telephoto lens / telescope idea


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<p>Hello all, I am thinking of making my own lens, yes my own lens and not as simple as pinhole lens or something.<br>

I have researched some and find some videos as well showing how hard (or easy) process it is to make a lens. Mot looking for top notch quality anyway closer to deal itself...</p>

<p>Dos anyone know what king of lenses do microscope have ? ( additive, positive, ...) It is definitely combination of lenses with different specifications. I am interested in this because the easiest way for telephoto optics is Galileo telescope (upside down telescope) in the way it works you have 2 lenses with different magnification : one small, for example 2x and other big, for example 6x then you combine then in different distances, I am thinking of using the small one from a microscope, may sound ridiculous but difference in magnification and tube length is the main thing that affects the resulting focal length and so on, other ways as well...<br>

So, do anyone have experience with building home made telephoto lenses ? Not talking about pinhole, holga or macro tubes.<br>

Any info will be useful so as this is the first time I will be trying something like this.</p>

<div>00dGfk-556558384.jpg.b8a3a5a60a97cc1923bd2e833b276617.jpg</div>

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<p>Your picture shows a reflector telescope, whereas telephoto lenses for cameras are of the refractor (also known as Gallilean) variety. There are lots of sources for materials out there to make either. Most inexpensive ones are achromatic, that is, they only focus 2 wavelengths of light at a point - so there is often a colored fringe around objects having high contrast with the background, whereas more expensive ones are apochromatic, focusing 3 wavelengths of light to a point. Before wasting your money....do a lot of research....optics seem simple in concept, but the nuances make a gigantic difference between a trashy result and an acceptable one. FWIW, you're much better off, for camera use, buying a good used telephoto lens....older manual focus ones are inexpensive and will run circles around anything you construct on your own....because sophisticated optical designs have been incorporated. Telephoto lenses for camera usage incorporate variable diaphragms, which often aren't part of simple telescope designs.</p>
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<p>+1 on Stephen's comments. From high school on I collected a variety of surplus optical assemblies, achromats, and aerial camera lenses. While these objective lenses worked fine as finder scopes on my telescopes, they were failures as telephotos. Look at cutaway diagrams of telephotos and compare with a basic telescope design which is an objective lens at one end of the tube and an eyepiece (or sensor) at the other end. The telephoto, in contrast, has a number of elements down the tube designed to reduce aberrations and produce an image that covers the entire film frame. Even the inexpensive Soligor and Spiratone lenses from 50 years ago will surpass most simple objective lenses for camera work. Of course, you can buy a multiple-element fluorite apochromat tube assembly, but that will cost you about as much as a 400/2.8 telephoto lens.</p>
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<p>Akbar, if you are intent on building a telescope and mount a camera to it, great. But do not consider it useful outside of astrophotography. On telescope building, look up Dobsonian telescopes. The style of mount they use is far superior to the pipe mount on your photo which will suffer from excessive vibration.</p>
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<p>A reflecting telescope such as pictured won't have any chromatic aberration, but it will suffer from varying degrees of coma, depending on how fast it is. Also, unless the focuser has a very long "travel" it won't be able to reach infinity focus with the camera if it can focus to infinity with an eyepiece. A long focal length mirror (around f8 to f10) might work, say for moon photography, but would be inconvenient for land photos. Also, unless well-baffled, contrast will suffer. Fast mirrors (f4 to f5) will have coma and by design will have a larger secondary mirror which will reduce contrast.</p>
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I have my first degree in physics and you are a man after my own heart when it comes to projects like this. The simple

mechanics are real simple but the devil

Is in the subtle details. The index of refraction

Is a very approximate number and varies over the electromagnetic spectrum. Thus with primitive systems you get that

rainbow effect with your images. There very best engineers in their respective times have never completely solved the

issue for all circumstances. Also if can can not allign the lenses perfectly parallel and along the apex you will have a

disaster with a telephoto lens. Then you need a competent mounting system to have the lens perpendicular to the film

bed. Then you need to deal with focal length and stop. I thought of this once and realized that it is not realistic. If you look

at some of my previous ideas you will see I have tried to improvise some very unique failures. Just go to Ebay and get the

cheapest lens you can find, It will work better than anything

 

 

you make and your time is worth a lot more than what you pay.

A pinhole will produce s much better result..

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<p>There is another current thread "Moon Shots" in the nature forum with the first image taken with the venerable Spiratone 400/6.3 lens. Acuity and contrast is good and, considering the cost of that lens on the auction sites, you will not save any money by building your own telephoto.</p>
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<p>Last I knew, there were still amateur telescope makers, usually reflectors. The process for grinding spherical mirrors is well understood. I believe it isn't so hard to make one good enough for amateur astronomy, but not good enough for telephoto photography.</p>

<p>I haven't thought about this recently, but I believe you adapt a camera to either a microscope or telescope without additional lenses. The focus is different, but it works fine. Maybe good enough for astrophotography, such as moon photography. </p>

<p>But there are so many quality telephoto lenses at rock bottom prices. I bought a Nikon AI 80-200 zoom for about $10. (Manual focus, but AF lenses aren't all that expensive either.)</p>

<p>The 500mm and 800mm mirror lenses from not so many years ago will do some that you might think about doing with a telescope, and you can add a 2x or 3x teleconverter. Again, find them on the usual auction sites. I recommend shopgoodwill.com, find your local store to avoid shipping costs.</p>

-- glen

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<p>+1 on the film-era telephotos.<br>

Take a look at the technique known as "Eyepiece Projection" with telescopes and cameras.<br>

Also take a look at using a mirrorless digital camera with a spotting scope (also refereed to as "Digi-Scoping"). </p>

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