I think the most interesting part of homemade telescope making is that you can check the curve of your homemade mirror to an accuracy of a fraction of a wavelength of light with a handful of common household items. You can do this using the Foucault knife-edge test [1] [2].<p>> It measures mirror surface dimensions by reflecting light into a knife edge at or near the mirror's centre of curvature. In doing so, it only needs a tester which in its most basic 19th century form consists of a light bulb, a piece of tinfoil with a pinhole in it, and a razor blade to create the knife edge.<p>Of course you don't need a light bulb. A candle will do. This means that once you have a level of technology that can make glass discs, candles, something opaque with a way to make a pinhole in it, something opaque with a thin straight edge, abrasive grit in a range of sizes, and some way to coat a glass surface with a thin layer of metal, you can make telescope mirrors.<p>Much of that could be done in ancient times. The only things on that list I'm not sure about are abrasive grit and coating the mirror.<p>You want a series of grits from coarse to very fine, and I have no idea when grit making became refined enough to have such a range of sizes.<p>Coating a mirror can be done with silver. Here are some instructions for doing it at home [3]. You need silver nitrate, ammonium hydroxide, potassium hydroxide, detergent, acetone, and nitric acid if you follow this instructions, plus assorted hardware like stirring rods, absorbent cotton, beakers and bottles, and that kind of thing. I think all of that goes back at least a few hundred years.<p>[1] <a href="https://en.wikipedia.org/wiki/Foucault_knife-edge_test" rel="nofollow">https://en.wikipedia.org/wiki/Foucault_knife-edge_test</a><p>[2] <a href="https://en.wikipedia.org/wiki/Amateur_telescope_making" rel="nofollow">https://en.wikipedia.org/wiki/Amateur_telescope_making</a><p>[3] <a href="http://www.webstertelescopes.com/silvering.htm" rel="nofollow">http://www.webstertelescopes.com/silvering.htm</a>
When I was a kid, I borrowed Jean Texreau's How to Make a Telescope from the library and read it from cover-to-cover many times.[1] I never did have the resources as a child to go ahead and actually build a telescope, but by reading the instructions I had the opportunity to live out the experience in my imagination.<p>This might make for an interesting quarantine project today ...<p>[1] <a href="https://www.willbell.com/tm/tm3.htm" rel="nofollow">https://www.willbell.com/tm/tm3.htm</a>
<a href="https://en.wikipedia.org/wiki/Dobsonian_telescope" rel="nofollow">https://en.wikipedia.org/wiki/Dobsonian_telescope</a><p>I once worked with a woman who learned from John Dobson about lens grinding and telescope construction. Watched a Youtube video of John recently. This is too labor intensive for me, but happy others enjoy it.
Another amateur (these days professional) telescope maker who started in his teens and has written in length and detail about his projects, Allar Saviauk: <a href="http://www.allarscopes.com/telescopes/index_eng.htm" rel="nofollow">http://www.allarscopes.com/telescopes/index_eng.htm</a>
When I was in high school I spent an entire summer grinding my own mirror out in the barn for a 6" Newtonian telescope. It was the most fun and satisfying project a kid can do. I bought the mirror blanks and basic parts from a mail order company (it was 1972) called Edmunds Scientific. They are still in business but they sell toys now, they have a serious branch <a href="https://www.edmundoptics.com/" rel="nofollow">https://www.edmundoptics.com/</a> but I don't think very many people grind their own mirrors any more.
When I tried to do this as a kid, I was stymied by the impressive costs of the kit involved. Has it become cheaper, or does this kid have enabling parents?
Dobsonians scale well; here [1] is Dr. Hänssgen's 42" telescope, which can be de/assembled and un/loaded for transport by one person.<p>[1] <a href="http://www.cruxis.com/scope/scope1070.htm" rel="nofollow">http://www.cruxis.com/scope/scope1070.htm</a>
I'd love to do something like this with my kid when they get a little older, but am always hesitant on the health risks on grinding the mirror. Can anyone shed light on the health risks if any?
Oh brings me back memories :) I did that at his age too. Dobsons are awesome, would dev a tracking system if I were 17 now (with a raspberry pie) keep on the good work!
That’s great! Certainly better than huffing glue or supporting communism or whatever most kids are up to these days.<p>But it would be more correct to say he assembled his own telescope, since it seems like he purchased all the important components, including the mirror.
Wow, a 17 year old did something... Why do people point out age, like we are supposed to be impressed. If it was a 2 year old that did this, I would be impressed.<p>While the act of what this person did is neat, but pointing out the age seems like useless info for a title.