[HN Gopher] Amateur Telescope Making Main Page
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Amateur Telescope Making Main Page
Author : Tomte
Score : 196 points
Date : 2025-03-13 10:43 UTC (12 hours ago)
(HTM) web link (stellafane.org)
(TXT) w3m dump (stellafane.org)
| nextts wrote:
| Like the 90s style photos. Colour profile were different on those
| old cameras right? Adds some character.
| Hokulea wrote:
| The website layout is kinda 90s too ;)
|
| Impressive stuff though, coming from a former professional
| astronomer who never built a telescope from scratch.
| paulbrowne wrote:
| 14 requests, 500kb total size
| chantepierre wrote:
| 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 l/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 :)
| bhickey wrote:
| 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.
| itishappy wrote:
| Fascinating! How are you fabricating the diffractive
| elements?
| chantepierre wrote:
| That's awesome, are you using lithographic processes to
| produce the diffractive elements ?
| bhickey wrote:
| 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.
| chantepierre wrote:
| That sounds about in line with a microlithography vendor
| (UK) I ordered zoneplates from. 7-10um features were
| accessible and going to 0.7um was an order of magnitude
| higher (and went from film to chrome on glass IIRC). File
| size was also a factor for more complex patterns.
|
| Do not hesitate to post results on cloudynights or your
| club's website, I'll refresh it from time to time ! I do
| not think I have enough diffraction experience to help
| though.
|
| Best of luck for your endaevor.
| ipbrown wrote:
| Do you have any photomask vendors that you recommend. I
| am trying to do some homebrew lithography and the
| photomask is not coming out as crisp as I want.
| carefish wrote:
| Pretty cool, how did you come about to start this as a hobby?
| SAI_Peregrinus wrote:
| It's worth noting that you can also use an interferometer as a
| very accurate thermometer[1]. 3D printing filaments are much
| more sensitive to temperature variation than metals, which can
| be bad if you're trying to get repeatable results & don't have
| good temperature control.
|
| [1] https://www.youtube.com/watch?v=vupIq4epCQA
| michaelwilson wrote:
| 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.
| exitb wrote:
| Thank you for posting that. I own a Dobsonian telescope, but
| never wondered about the figure behind its name.
| michaelwilson wrote:
| People don't talk about it now but when he first started the
| "established" telescope making folks spoke derisively of him,
| his techniques, and his telescopes.
|
| Why?
|
| To start with "we" - he and his students - made the mirrors
| out of old portlights (the glass in portholes), so it was
| "assumed" they would flex (since they were thinner than
| store-bought mirror blanks) and would be subject to thermal
| issues.
|
| Then of course was the fact the telescope tube was made out
| of a heavy cardboard concrete form called a "Sonotube", which
| you'd waterproof and paint - paint color and pattern choice
| being one of the most creative parts of the project. The
| "diagonal" - the mirror which directed the light path
| 90-degrees out to the eyepiece - was mounted on a 1"-2" dowel
| with 3 slots cut into it and held in place by wood shingles.
|
| The mirror mount itself was a 3/4" piece of plywood with 3
| bolts in it, which you'd use to collimate the mirror once it
| was mounted in the tube.
|
| And then the mount. Not only was it "alt-azimuth", it was
| made of plywood. You built a box around the tube, and two
| circles on the box fit into 1/2 circles in the mount.
|
| There are more details on the Stellafane page -
| https://stellafane.org/tm/dob/index.html - but those are even
| fancier than the ones we made!
|
| But Dobson's ultimate heresy was his approach to figuring the
| mirror:
|
| Instead of using a "Foucault Tester" to measure and figure
| the mirror, he'd mount the polished mirror in the telescope
| and point it at a point source of light - usually the sun's
| reflection off a ceramic power line insulator.
|
| By moving the image in and out of focus and looking for
| bright rings in the image, you could tell the shape of the
| mirror and whether is had hills or valleys in the figure. The
| end result was a parabola accurate to 1/2 or 1/4 wave (he
| said he could get it to 1/10th wave, and I have no reason to
| doubt it).
|
| To the folks used to using much fancier foucault or even more
| advanced testing methods on much more expensive mirror blanks
| this was impossible and widely derided and, frankly, made fun
| of. People weren't very nice.
|
| But when they took the mirrors and tested them with their
| foucault and diffraction testers they got a big surprise -
| the curves _were_ accurate and of high quality. And, _big_ -
| people regularly made 16" telescopes this way, and the San
| Francisco Sidewalk Astronomers had a portable 24" for
| goodness sake.
|
| (I think people kind of forgot he used to be a physicist, and
| probably knew a thing or two about light).
|
| The other big beef was the alt-azimuth mount. Not only did it
| not have setting circles to find things in the sky by RA and
| Dec, it wouldn't automatically track, so it could never be
| used to take pictures (you can get Dobsonians which will do
| that today natch now that we have computer controlled
| stepping motors).
|
| But the point was _none of that mattered_: He wanted to make
| telescopes for people to look through, not take pictures
| with. So if he could build a telescope he could wheel out
| into Golden Gate park, set up in 15 minutes, and have 100
| people see stars, planets and nebulae, that was The Win.
|
| And teaching regular people - including kids - of both
| genders - how to make their own telescope, well that was
| almost as good. A big part of that was it was _affordable_,
| which meant many, many more people could make telescopes than
| otherwise. In Dot-Com vernacular, he grew the TAM (Total
| Addressable - or would that be Astronomical - Market), well,
| astronomically.
|
| (Bada-Bing, I'm here all week folks).
|
| But seriously, I can tell you from experience, no
| astrophotograph you take will ever, ever, compare to seeing
| Saturn, or M31, or any one of many other things with your own
| eye, and in a telescope you built.
|
| Sorry for the long screed - got started and stirred up some
| memories there.
| tejtm wrote:
| No worries, he got me too. No I do not subscribe to
| everything he thought on a cosmological level but the
| importance of vintage photons direct to brain for everyone
| resonated.
|
| Bringing telescopes out of the rarefied world of
| astronomers where they were "precious" to professional and
| amateur alike is what I see as his greatest legacy.
|
| I build "public friendly" scopes as a result. If anyone is
| thinking of a new mount for a Newtonian may I suggest
| looking up "Sudiball" mount as they allow you to
| accommodate a wider range of eyepiece heights for a given
| target. (so parents are less likely to put their kids in a
| half-nelson screeching "DON'T TOUCH DON'T TOUCH" as they
| poke them in the ear with your scope)
| gooseus wrote:
| 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
| gabeio wrote:
| 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. There are tons of
| things to do. They also have a competition which judges on
| various aspects of telescopes. I have really enjoyed growing up
| around this convention.
| alberth wrote:
| Slightly OT: there is a total lunar eclipse today/tomorrow for
| many around the world.
|
| https://svs.gsfc.nasa.gov/5473
| Joe_Cool wrote:
| 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.
| nvalis wrote:
| 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
| chasd00 wrote:
| 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.
| megadata wrote:
| 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.
| vibrolax wrote:
| I spent 25+ years in the precision optics industry, a large
| portion of which was building machines and instruments for
| fabricating and testing aspheric lenses and mirrors. Designing,
| performing, and validating null tests is technically
| terrifying. Not only is the clock ticking, but every operation
| on the artifact carries a risk of destroying it, or making it
| unusable.
|
| It's not life-and-death, but it's pretty satisfying nerd work.
| noelwelsh wrote:
| I saw this post today:
| https://bsky.app/profile/martin.kleppmann.com/post/3lkax2h5v...
|
| Real amateurs modify their whole house to fit in the telescope,
| apparently.
| nickvec wrote:
| JFYI, there's a total lunar eclipse occurring tonight that will
| be viewable across the continental United States. Don't miss the
| blood moon!
| jacknews wrote:
| You don't even need to grind your own mirror to get in on the
| action.
|
| Younger I made a 6" scope from a bought mirror set, and the first
| time I used it I caught one of Jupiters moons occulting in
| realtime.
| lifeisstillgood wrote:
| I'm almost afraid to ask on this thread but if a dad wanted to
| purchase a simple telescope that would be good enough to see say
| Jupiter, or Mars on a decent night in the UK to try and ref the
| kids excited, where does one start? I have dived into some sites
| but I think I am asking the wrong questions
| chantepierre wrote:
| If you want a purely visual experience (which I recommend), a
| dobsonian telescope has the best capability VS price ratio. The
| collapsible 150mm dobsons are already very powerful and quite
| compact. Avoid anything on a tripod under 500$, you'd be paying
| the "looks like a telescope" tax and have something deceptive.
| tejtm wrote:
| Perusing Stellafane's pages is likely as good as it gets for
| both a broad and thorough introduction. As with many things, it
| is an art of trade offs.
|
| Aperture rules until the work to set up means it sits unused.
|
| The objects you mention are bright (and small) and can be seen
| in anything, including nothing, which fills department stores
| with small scopes known to amateur astronomers as "Hobby
| Killers".
|
| So immerse yourself a bit, pick up some language and basics,
| then find a local club to try before you buy, clubs or generous
| members may have a loaners scopes so you can figure out where
| you want to be on the what you can see v.s how much effort you
| can put in scale.
|
| cheers
| relwin wrote:
| Ed Ting has a good beginner's guide:
| https://youtu.be/NvslqVTNEWs?si=VG5YIDzELf9iSOx0
| helij wrote:
| If you have a garden 8" Dobsonian or even larger if you can
| handle it. If in a flat a 4" Apochromatic refractor. Mars can
| be so so but good views of Jupiter, Saturn and Luna can be had
| in the UK. Both good for double stars as well and even deep sky
| objects if in a low light pollution area.
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