Telescope making is much alive and there are communities of people (even young people) making their first mirrors right now. Most find their entry in the hobby via the forums (CloudyNights's ATM, Optics & DIY forum, Stargazerslounge, Astrosurf, Astrotreff.de) and amateur mirror maker Discord channels are popping up.
I also recommend anyone wanting to grind their first mirror to read about modern ways of testing in addition to all the classic books (Texereau, Sam Brown, Lecleire) about mirror making.
Bath interferometers changed the game and allow to reach λ/10 wavefront with certainty and repeatability compared to Foucault testing. They are affordable and there's a healthy community around DFTFringe, the de-facto standard interferogram analysis software at interferometry.groups.io
You can also find a Foucault + Ronchi + Bath combo tester's plans on Printables.com and a companion three-axis-table, allowing great testing ergonomics for a low cost if you have access to 3D Printing.
The best resources on how to setup a Bath Inteferometer can be found on the GAP47's website (french, but machine translatable) and GR5's YouTube channel.
My club, the Amateur Telescope Makers of Boston (atmob.org), holds weekly mirror grinding sessions at our clubhouse. Along with another club member I'm working on a diffracting telescope and hope to see first light this spring.
Yes, I'm using a photomask vendor to fabricate the objective. It's in the low hundreds of dollar to get 7um features, a bit more expensive to reach 4um and bloody murder to get 1um (~thousands).
Currently we have some tiny photon sieves, around 1.5mm aperture ~f/14. The next step is going up to 60mm @ f/6.5. The end goal, and I don't know how achievable this is, will be a very large aperture panelized scope. We've discussed making something unsteerably large, sticking it in a field and using the Earth's rotation to sweep the sky.
There's a little bit of trickery to reduce harmonics, though I'm not sure how it'll perform in practice. Please get in touch if you have experience doing diffraction simulation. After first light I plan to write everything up.
I made my first 10" telescope - rough and fine ground, polished, figured, and built the telescope and mount at 10 under the instruction famous (later) John Dobson in San Francisco. It's not hype to say he was one of the most significant figures in popularizing astronomy in modern history.
I later went on to make a 16" and then "fell off the wagon" and bought refractors, equatorial mounts and cameras. But I never could have gotten started without him.
There is a very detailed video documentation [0] about telescope building techniques, featuring insights from John Dobson, the inventor of the Dobsonian telescope mentioned on the page.
I worked at an educational robotics small business in DFW in the late 90s. My boss was super into amateur astronomy and made his own telescopes. Those guys remind me of the amateur rocketry people. Incredibly skilled and knowledgeable group of hobbyists.
I'm always amazed when I see a site that looks like it was built in the early 00s that is still being kept up to date with their Events and News pages.
I am a member of Stellafane (STMs). The convention every year is amazing. It’s so fun to be surrounded by people who are so interested in astronomy that they travel to a convention out of their own state!
The keynote speaker last year was talking about the James Webb Telescope build, absolutely fascinating.
I ground an 8" mirror in my living room using Jean Texereau's book as a guide (i.e., pre-YouTube). A plastic garbage bag on the floor handled any wet grit. I don't understand what grinding dust you experienced - the grit is always wet. It was a great experience and thrilling to see the view even before the mirror was aluminized.
I'm truly sorry for your experience. A first mirror can be a lot of process and can indeed get a bit messy. With experience (or guidance, which is even better) you can work cleanly and avoid glass dust contamination of your workspace.
A bit messy is understatement. And finishing such project without a good guidance is almost impossible. At final stage a few bad moves can destroy week of work!
It is setting up newcomers for failure and burnout.
We made our own mirrors, because there was no other option a few decades ago.
But today mirrors are cheap, and they come with aluminum coating and rest of the telescope!
It's not about price, but enjoying the process, or making instruments that just are not commercially available. Amateurs are constantly pushing the limits of optical designs.
Just because this was your experience does not mean others should not try, and frankly, your posts suggesting others not try is disgusting. You're on a forum for people with a hacking ethos. That's pretty much the "hold my beer" mindset with a facade of classiness in front of it.
Also, rather than saying such negative things like "don't do it", you could have wrapped up your negative experience into a parable for people to learn from before embarking upon their own journey. Just because you didn't prepare for the results of grinding something to a fine dust/powder doesn't mean others won't prepare for that. Especially after what could have been a much more positive outcome from your negative experience. Don't be a downer.
This would be haha funny if you were trying to stoke that "don't tell me no" as reverse psychology.
This is a bummer as I had been thinking about grinding my own for some time now. I'd like to know more about it and how I can protect myself.
The only part of the wikipedia for Silicosis that mentions glass is about manufacturing it and, even if it includes the grinding part, the reference it links to doesn't mention glass or grinding at all.
If you have more pointers or keywords about this subject, please let me know!
So don't have your pets in the workspace when it's not safe for them. What kind of lousy pet parent are you to not consider that? Also, wear the proper breathing equipment. This isn't some lame COVID anti-masking thread where wearing a mask says something about your politiks. It's working in a less than ideal environment, so take the proper precautions.
This is like telling people not to go outside because the dangers of UV radiation are too much. Deal with it. Wear protective clothing, don't hide in a cave. Some of us are brave enough and have the ability to judge risk/reward so that we left the cave, we crossed the oceans, we've left the planet. I'd hate to live in a world were nobody did anything risky because someone previously had a bad experience and stopped rather than looking at the bad result, making changes, improving the outcome the next time.
Telescope making is much alive and there are communities of people (even young people) making their first mirrors right now. Most find their entry in the hobby via the forums (CloudyNights's ATM, Optics & DIY forum, Stargazerslounge, Astrosurf, Astrotreff.de) and amateur mirror maker Discord channels are popping up.
I also recommend anyone wanting to grind their first mirror to read about modern ways of testing in addition to all the classic books (Texereau, Sam Brown, Lecleire) about mirror making.
Bath interferometers changed the game and allow to reach λ/10 wavefront with certainty and repeatability compared to Foucault testing. They are affordable and there's a healthy community around DFTFringe, the de-facto standard interferogram analysis software at interferometry.groups.io
You can also find a Foucault + Ronchi + Bath combo tester's plans on Printables.com and a companion three-axis-table, allowing great testing ergonomics for a low cost if you have access to 3D Printing.
The best resources on how to setup a Bath Inteferometer can be found on the GAP47's website (french, but machine translatable) and GR5's YouTube channel.
Have fun :)
My club, the Amateur Telescope Makers of Boston (atmob.org), holds weekly mirror grinding sessions at our clubhouse. Along with another club member I'm working on a diffracting telescope and hope to see first light this spring.
That's awesome, are you using lithographic processes to produce the diffractive elements ?
Yes, I'm using a photomask vendor to fabricate the objective. It's in the low hundreds of dollar to get 7um features, a bit more expensive to reach 4um and bloody murder to get 1um (~thousands).
Currently we have some tiny photon sieves, around 1.5mm aperture ~f/14. The next step is going up to 60mm @ f/6.5. The end goal, and I don't know how achievable this is, will be a very large aperture panelized scope. We've discussed making something unsteerably large, sticking it in a field and using the Earth's rotation to sweep the sky.
There's a little bit of trickery to reduce harmonics, though I'm not sure how it'll perform in practice. Please get in touch if you have experience doing diffraction simulation. After first light I plan to write everything up.
Fascinating! How are you fabricating the diffractive elements?
Slightly OT: there is a total lunar eclipse today/tomorrow for many around the world.
https://svs.gsfc.nasa.gov/5473
Sadly under the horizon for me. But it's raining anyways.
Better luck next time to anyone around here and happy eclipse to the people that can enjoy it.
Not amateurs, but a NASA contractor managed to mess up Hubble's mirror back in the day.
Involves chipped paint and household washers.
https://hackaday.com/2020/04/29/test-equipment-shim-washers-...
Simon Winchester also covers it in great detail in his book Exactly: How Precision Engineers Created the Modern World
If you're interested in precision making and how it all came to be it's a very joyful read.
I made my first 10" telescope - rough and fine ground, polished, figured, and built the telescope and mount at 10 under the instruction famous (later) John Dobson in San Francisco. It's not hype to say he was one of the most significant figures in popularizing astronomy in modern history.
https://en.wikipedia.org/wiki/John_Dobson_(amateur_astronome...
I later went on to make a 16" and then "fell off the wagon" and bought refractors, equatorial mounts and cameras. But I never could have gotten started without him.
Thank you for posting that. I own a Dobsonian telescope, but never wondered about the figure behind its name.
There is a very detailed video documentation [0] about telescope building techniques, featuring insights from John Dobson, the inventor of the Dobsonian telescope mentioned on the page.
[0] https://www.youtube.com/watch?v=snz7JJlSZvw
I worked at an educational robotics small business in DFW in the late 90s. My boss was super into amateur astronomy and made his own telescopes. Those guys remind me of the amateur rocketry people. Incredibly skilled and knowledgeable group of hobbyists.
I'm always amazed when I see a site that looks like it was built in the early 00s that is still being kept up to date with their Events and News pages.
Btw, for those very interested it looks like they have a yearly convention in VT, with registration opening May 1 — https://stellafane.org/convention/2025/index.html
I am a member of Stellafane (STMs). The convention every year is amazing. It’s so fun to be surrounded by people who are so interested in astronomy that they travel to a convention out of their own state!
The keynote speaker last year was talking about the James Webb Telescope build, absolutely fascinating.
Like the 90s style photos. Colour profile were different on those old cameras right? Adds some character.
The website layout is kinda 90s too ;)
Impressive stuff though, coming from a former professional astronomer who never built a telescope from scratch.
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I ground an 8" mirror in my living room using Jean Texereau's book as a guide (i.e., pre-YouTube). A plastic garbage bag on the floor handled any wet grit. I don't understand what grinding dust you experienced - the grit is always wet. It was a great experience and thrilling to see the view even before the mirror was aluminized.
I'm truly sorry for your experience. A first mirror can be a lot of process and can indeed get a bit messy. With experience (or guidance, which is even better) you can work cleanly and avoid glass dust contamination of your workspace.
A bit messy is understatement. And finishing such project without a good guidance is almost impossible. At final stage a few bad moves can destroy week of work! It is setting up newcomers for failure and burnout.
We made our own mirrors, because there was no other option a few decades ago.
But today mirrors are cheap, and they come with aluminum coating and rest of the telescope!
It's not about price, but enjoying the process, or making instruments that just are not commercially available. Amateurs are constantly pushing the limits of optical designs.
Here is a recent groundbreaking example from Rik Ter Horst, a 10" f/20 kutter with toroidal secondary : https://www.cloudynights.com/topic/935825-a-250-mm-f20-kutte...
I did not do anything that impressive but enjoy my own set of non-standard scopes :
- A 8" f/3.5 hyperbolic primary + ross corrector
- a 6" f/2.8 with permanently mounted 4-element corrector
and am working on a 16.5" f/3.3 that will have a permanent Paracorr II lens group.
The only messy moment was my first mirror when I learned to cut pitch, but grit and glass dust itself are no problem thanks to the wet process.
You are right though on the last bits of figuring, it's a psychological challenge and my first mirror took 3 attempts over 18 months.
I'm not in the loop, are 14 inch or larger mirrors affordable nowadays?
16" dobsonian in Germany, 2175 euro including taxes. It comes with EU warranty.
https://www.teleskop-express.de/en/telescopes-4/dobsonian-te...
Just because this was your experience does not mean others should not try, and frankly, your posts suggesting others not try is disgusting. You're on a forum for people with a hacking ethos. That's pretty much the "hold my beer" mindset with a facade of classiness in front of it.
Also, rather than saying such negative things like "don't do it", you could have wrapped up your negative experience into a parable for people to learn from before embarking upon their own journey. Just because you didn't prepare for the results of grinding something to a fine dust/powder doesn't mean others won't prepare for that. Especially after what could have been a much more positive outcome from your negative experience. Don't be a downer.
This would be haha funny if you were trying to stoke that "don't tell me no" as reverse psychology.
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Do you have a reference on the health hazard aspect you mentioned? I'd heard fiberglass dust is very bad, but not regular glass.
I guess it is about https://en.wikipedia.org/wiki/Silicosis
Silicosis, but also fine dust is toxic when ingested. It can literally kill your cat or dog!
This is a bummer as I had been thinking about grinding my own for some time now. I'd like to know more about it and how I can protect myself.
The only part of the wikipedia for Silicosis that mentions glass is about manufacturing it and, even if it includes the grinding part, the reference it links to doesn't mention glass or grinding at all.
If you have more pointers or keywords about this subject, please let me know!
So don't have your pets in the workspace when it's not safe for them. What kind of lousy pet parent are you to not consider that? Also, wear the proper breathing equipment. This isn't some lame COVID anti-masking thread where wearing a mask says something about your politiks. It's working in a less than ideal environment, so take the proper precautions.
This is like telling people not to go outside because the dangers of UV radiation are too much. Deal with it. Wear protective clothing, don't hide in a cave. Some of us are brave enough and have the ability to judge risk/reward so that we left the cave, we crossed the oceans, we've left the planet. I'd hate to live in a world were nobody did anything risky because someone previously had a bad experience and stopped rather than looking at the bad result, making changes, improving the outcome the next time.