The tiniest yet real telescope I've built

Posted by chantepierre 5 hours ago

Comments

Comment by ramblin_ray 9 minutes ago

Nice!! I printed a very similar (but larger) telescope back in 2018 with similar results... I didn't research my mirrors well and ended up with bad ones. Plus, it wasn't very stable at that size. I'd imagine a smaller version would be much more stable... Thanks for sharing!!

https://yesteryearforever.xyz/ABSDBS

Comment by chantepierre 5 minutes ago

This is the first time I've seen a build of the ABSDBS in the wild, thanks for sharing ! Sadly an 8" f/4 mirror has a very narrow range of acceptable optical quality :/. It's too bad you ended up with a bad one. Maybe refiguring it would be a great followup project though

Comment by chantepierre 5 hours ago

Hello, author here ! Other interesting builds or projects going on in the french amateur telescope maker community :

  - Sunscan, by the STAROS team : a fully integrated open-source solar imaging kit : https://www.sunscan.net/fr  

  - Eric Royer's binocular 24" dobson : http://www.astrosurf.com/topic/124758-bino600/  

  - The Slim400 by Laurent Bourrasseau : https://www.cloudynights.com/forums/topic/920950-the-slim400/  

  - Astrowl, an electronically enhanced astronomy kit : http://www.astrosurf.com/topic/151807-projet-astrowl-de-visuel-assist%C3%A9/  

  - The smallest, an open-source 6" portable dobson : http://www.astrosurf.com/topic/176898-un-dobson-150-f5-facile-%C3%A0-imprimer-et-assez-compact/

  - A dedicated astrophotography power supply : https://github.com/Antiath/Open-Power-Box-XXL

Of course there are many others but those are the one on the top of my head now

Comment by waerhert 3 hours ago

Very cool, thanks for sharing! Any ideas of adding 2 gimbal motors to this for GOTO? MS6010v3 or something lighter would seem like a good fit.

Comment by fransje26 4 hours ago

Thank you for the links and the write-up!

I'll share them with a friend who loves astronomy and who loves to organize star-gazing events that he livens up with his Unistellar telescope.

Comment by 9Mfhf34U 4 hours ago

Do you have an RSS feed just for the astronomy posts on your blog?

Comment by chantepierre 4 hours ago

No, but that should be quite straightforward to add with Astro, I will check that.

  Edit : it seems that I now do have one : https://lucassifoni.info/blog/tag/astronomy/rss.xml

I am not an RSS user myself, I tested it with an online reader and it should be working.

Comment by Nition 5 hours ago

I always love the moment in blog posts like this, where the writer with their esoteric knowledge of the project will say something like "I almost considered reflaboring the exahenge, but of course it would be a ridiculous prospect for a project of this type". And then always, inevitably, there is the followup edit; "I reflabored the exahenge."

Too rarely in life are things made better than practical consideration would dictate, just because of dedication to the craft.

Comment by chantepierre 5 hours ago

Your comment brings me back to my first mirror making adventure, I was absolutely overwhelmed by the jargon and acronyms used by the mirror making community... a few years later I internalized it and use it as if it was common knowledge. I should put little explanations or details in my posts.

Comment by Nition 4 hours ago

There was enough there for me to get the basic idea, which is fine I think. Can't really expect every niche post to have all the details necessary for a general audience and it's fun to get a glimpse into these worlds anyway.

Thanks for sharing the post!

Comment by awesome_dude 5 hours ago

A friend of mine once told me - learning a new field is all about learning the language of that field

Comment by macintux 1 hour ago

A friend of mine asked me why we have such precise terminology in IT; I asked her why English has so many different words for "chair".

Comment by eru 4 hours ago

That's a big part of it, but far from everything.

Comment by awesome_dude 3 hours ago

I'm not really sure - I deliberately stopped there because the concepts related to that field are a part of the language learnings.

Comment by jiggawatts 3 hours ago

What they hear:

"Exorcise the lattice hoard to siphon the new incarnation."

What we said:

"Purge the web cache to download the new version."

Comment by aa-jv 1 hour ago

I just love the fluent use of terms, and the whole ontology of the subject itself just seems so appealing to me. For a moment, I felt like others feel when listening to me and my colleagues discuss kernel build issues or other software challenges - befuddled, bemused, enchanted.

I guess, if/when I retire to that remote mountain hideaway, I might just get into this hobby. The idea of grinding my own mirrors to look at dew on the spiderwebs of the neighborhood is just so appealing.

Comment by isolli 4 hours ago

Very nice! But you won't beat this ;)

> Optical Engineer Rik ter Horst shows us how he makes very small telescopes (at home) which are intended for use in micro-satellites.

https://www.youtube.com/watch?v=HxwhCmO90UQ

Comment by chantepierre 4 hours ago

Rik's monolithic Cassegrains are the perfect example of the blend of amateur and high-end professionnal work in astronomical optics, thanks for linking it ! His amateur work is incredible, like this 16" CDK : https://www.cloudynights.com/forums/topic/558284-a-400-mm-f1...

Comment by jiggawatts 3 hours ago

Dayyum, those shots are incredible! I've seen worse pictures from professional telescopes.

Comment by tejtm 3 hours ago

This coming year ... if the crik don't rise (as it does with some regularity). Some of you may be able to take a picture of yourself with one of Ril ter Horst lenses as it will be launched in a 2U cubesat named OreSat1 by Oregon's Portland State University undergrads.

https://www.oresat.org/home

pictures would be captured by hand held groundstations

https://www.oresat.org/technologies/ground-stations

Comment by danhau 4 hours ago

Came here to link this, but you beat me to it :)

Comment by seanrrr 30 minutes ago

Very cool project! I always wanted a telescope as a kid but kind of forgot about that desire as an adult. Didn’t know you could build your own like this.

Comment by chantepierre 28 minutes ago

If you want to commit to a build, this one is thought to be user-friendly and a great first instrument : https://www.printables.com/model/1325533-smallest-telescope-...

Comment by seanrrr 25 minutes ago

Thank you! Will check it out!

Comment by 2b3a51 3 hours ago

Roughly similar in size to the ones Newton made for the Royal Society as demonstration instruments.

https://en.wikipedia.org/wiki/Newton%27s_reflector

Very nice and I might look for one of these mirror kits.

Comment by ggm 4 hours ago

When did buying a mirror on Ali overtake grinding your own? I guess when Ali became Edmund scientific ie mirror grinding hasn't been a thing since I was in shorts (the 70s)

Comment by buescher 42 minutes ago

If you just want a serviceable telescope, you haven't been able to really save any money by grinding a mirror for decades, unless you're a madman like Dobson who scrounged blanks in the form of things like porthole windows. But that's not why people do it. I haven't built a non-trivial telescope but it is not too unusual for amateur telescope makers to figure mirrors to precision that you can't easily buy, i.e. not for amateur prices. Where he talks about Ali mirrors being l/6 or better? That's really good for randomly buying something unspecified cheap on Ali. l/6 is lambda/6 which means the surface error of the mirror is less than 1/6 a wavelength of light. Utility optics are typically l/4. Really fine stuff is l/10 or l/20.

Comment by chantepierre 33 minutes ago

I will correct the article, I've found great λ/6 or better spheres on Ali, but have yet to get a well corrected mirror. But starting from a λ/6 sphere instead of a flat glass blank saves so much time !

For this specific mirror, I was a bit disappointed, because it was specifcally advertised as parabolic, which made this project suitable, because coating costs trump all other costs for very small builds. Well it was 1.7x too much parabolic, and now I have to pay a coating :)

Comment by mapt 57 minutes ago

Mirror grinding is still a thing. Just not a thing that young people generally do. Distribution got easier and real estate got more scarce. Those of us who have garages, have filled them up.

In my understanding it's gotten considerably easier over the years with better availability of diamond and CBN abrasives, and with more electronic control of the grinding hardware. Slumping glass and bonding a thin sheet to ceramic foam reduced the costs and weight a great deal as well. Mastering these techniques make it easy to start a small business rather than to do a one-off in your garage, though.

As a sidenote: The Celestron RASA astrographs are so effective and so inexpensive of a wide-field instrument that it's a lot harder to justify the DIY activity that existed in the 2000's.

Comment by chantepierre 35 minutes ago

There is quite a vibrant community of young people grinding mirrors, it just has displaced to Discord. The "Observational astronomy" discord server has a lot of late-teenagers and young adults grinding. Our french Astro-FR server has people in their thirties grinding. But as you pointed out, garages are sparse and people seem to take shortcuts : finding bad pre-polished mirrors as blanks, slumping glass sheets to shape and continuing with fine grinding...

Comment by chantepierre 4 hours ago

We buy pre-dug mirrors on Ali to refigure them, or dig and figure our own all the time. See Ali as a supplier of prepolished blanks :) . The l/6 I mentioned in the post are l/6 spheres, so they also need figuring.

Comment by LtdJorge 2 hours ago

Very cool blog, not just post

Comment by upvotenow 4 hours ago

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