Astronomy Cast Ep. 327: Telescope Making, Part 1: Toys and Kits

by Fraser Cain on December 23, 2013

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Why pick up a low quality, wobbly telescope from the department store when you can craft your own – just like Galileo, and all the great astronomers from history. For a minor investment, you can build a worthy telescope out of spare parts and high quality kits.

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Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

Jon Kirwan December 25, 2013 at 5:35 AM

It’s been a long time since I ground mirrors. At that time there were, I think, five periodicals that were dedicated to the practice (some were bimonthly or quarterly, though) and Sky & Telescope had regular sections for this. I believe I searched perhaps 20 suppliers or more of hobbyist quantities of pretty much any kind of glass you can name, in various “qualities,” as well. In short, the practice was served reasonably well.

Today? I’m not aware of any periodical dedicated to making a telescope mirror and/or lenses, providing construction articles and designs for those unable to design, and providing design tutorials for those who are learning. Last I checked, WIllmann-Bell was the only supplier of mirror blanks and their choices are almost nil. Where might I get a maksutov corrector blank today?

Coulter was pushing their Dobson, but they sold glass. Jaegers was pushing value added glass, but you could get raw glass if you asked politely. Willmann-Bell had a much larger selection, including if I recall at some point correctly, a few different Maksutov corrector blanks in the rough.

I sat glued to studying construction articles by author after author, month after month. I studied optics, purchased all the usual books including Texereau’s and the 3-volume Amateur Telescope Making. I studied Texereau’s book front to back and selected articles in the 3-volume set. And then I sat down and set up testing facilities including the simple Foucault test and Ronchi method using gratings.

I’ve wanted to teach my children and grandchildren some of the pleasures of first learning to make, test, recognize various aberrations of different orders, and correct them appropriately. But after some calls, with responses like “Well, how many tons of that do you want?”, I’ve run up against the modern “fact” that companies catering to small quantity, hobbyist buyers of different types of roughly shaped (low value-added) glasses of differing types is as dead as the dinosaurs. Used to be, plenty of businesses serving that area. No longer.

It’s my opinion you cannot really understand well what you are observing if you don’t know about aberrations, their causes and remedies, and have some personal, practical experiences. Just buying something off the shelf, no matter how good it is, will never teach you these things and you cannot well know what you are getting.

I’ll be watching to see if you folks can show me my errors and point out where I can buy a wide array of telescope making supplies in hobbyist quantities. For example, I’d like to consider making a maksutov binocular with objectives of about 150mm. (I’m consider either Gregory “spot” or Cassegrain.) Any ideas? Love to see them. And no, I will not buy a completed unit. I’ll design, grind, test, and figure myself. And construct the mechanicals, as well.

I’ll leave it there and watch with hope.

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