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Wallace the 6 inch f/2.8 telescope, building it, and hiking with it
147 points by chantepierre 4 days ago | 29 comments
  • zonkerdonker
    Very cool project and video documentation, really inspiring! As someone who is mechanically inclined and has a decent amount of tools/3D printer, is there any DIY telescope that you would recommend to build as a first foray into the field?

    I've never done much with optics, and after reading through a few of your posts, it looks both incredibly challenging and very rewarding.

    • chantepierre
      To me, there are two models that stand out from the crowd :

      - The Hadley, a 4"1/2 f/9 dobsonian telescope, which is a smaller aperture but easy to build and to find optics for, and very mature : https://www.printables.com/model/224383-astronomical-telesco...

      - The "open smallest telescope" from a friend, which I show here, a foldable 6inch f5 dobsonian : https://lucassifoni.info/blog/2025-best-6-inch-f5-150-750-po... and can be found on Printables : https://www.printables.com/model/1325533-ost-open-smallest-t...

      Both are very cool projects, the smallest shows more for deep sky but costs a bit more in optics, and the Hadley has a very mature community.

    • bluGill
      How into this will you get? If you just want to make your own a small telescope is easiest (see the other reply). As things get large expenses go up. Commercial lens are cheap for smaller telescopes, but as you get to large that becomes the cost and so making your own is the only way you can afford it. If you want a large telescope you should again start making a small one, but this time making your own lens - even though it isn't cost effective to make your own lens (vs buy), the experience means you have a chance to make a larger one (and finish, most people who set out to make one large telescope never finish, those set out to make a small and then a large are more likely to finish both).

      If you just want to see the stars, goodwill often has telescopes cheap. A refactor can see more than your eye. (or even the binoculars you likely already have!). And the bigger reflectors are seen once in a while.

    • GloriousKoji
      I built a Hadley 114 over the course of 3 weekends and I highly enjoyed it. Amazon has a convenient 2 piece mirror kit you can buy. The rest of the parts (springs, screws, rods) can be acquired anywhere and the stand can be as complex or as simple as you want.
    • giantg2
      Just go down the rabbit hole like I have over the past year...

      Find thick glass on Facebook, build a cutting jig, build a kiln to fuse it, etc. I'm still planning to build an 18".

  • mybbor
    Love this. Thanks for sharing. My friend and I pulled an old Dobsonian telescope of my Dad's from the garage when we were teenagers. We spent hours and hours out with it under the stars, and on cloudy nights I would read a book about telescope construction. Back then, cabinet makers were building the most impressive wood frames. Interesting to see how the technology has changed.
    • dylan604
      > cabinet makers were building the most impressive wood frames

      You say impressive, but my mind reads that as heavy even if they looked amazing

      • mybbor
        Yeah! I meant impressive more in the “big sturdy woodwork” sense, not lightweight. They had to hold a heavy mirror and still move smoothly enough to aim by hand. The Dobsonian design, plus Teflon on Formica bearings, made big aperture amateur telescopes way more accessible to hobbyists. From what I gathered it was definitely a “bigger is better” kind of thing, and weight seemed pretty secondary.
        • chantepierre
          We still do it ! But the designs have evolved, see : https://www.youtube.com/watch?v=SWhxCwHVPms

          I'm planning this kind of build for my 16". It's still a dob, still uses teflon against formica and a wood structure, but the ability to move it easily indeed became a desirable feature.

  • thenthenthen
    Very cool, any pictures of the images it produces?
  • rom16384
    Quite an impressive build. How hard is it to collimate the telescope? Does it hold the collimation?
    • chantepierre
      Hi ! It is quite easy, with 2 tilt screws at the secondary cage, and the primary cell floats on three heavy duty springs. I can shake it and nothing moves, this is my first criteria. I collimate with a cheshire tool but always finish on a star at medium power (since this telescope realistically does not reach high power, since it would need 2mm eyepieces which are the opposite of wide field views). I use it with Explore Scientific 17mm 92 degree, and a 13mm APM XWA 100 degree eyepieces, and do star collimation with a 6.7mm eyepiece.

      So most of the use is at 25x, to frame huge objects like NGC7000 or the largest extensions of M31

      • helij
        Barlow!?
        • chantepierre
          Well, I could, but checking collimation at 1-2D magnification for an instrument used at 0.16D provides no observable advantage once star collimation was done. My rule of thumb is to star collimate at a higher power than actually used to observe
  • petee
    Beautiful, like I needed a new crossover of hobbies; btw could this fill a 220 format frame?

    You also could save a lot of weight by boring out your plywood base and still be plenty rigid

    • chantepierre
      I'm sorry, I did not find what you meant by a 220 format frame. Is it a film photography type ?
      • platinum95
        220 is a roll film, essentially the same as 120 film, just a longer roll. It's 6cm wide, and picture format depends on the camera/lens, varying from 6x4.5 up to 6x7 (and beyond, for panoramic shots).

        So for use with your telescope, it'd need to produce an image circle that'd cover at least 6cm.

        • chantepierre
          Thanks for the clarification. I don't think so, my largest eyepiece has a field stop of 39mm, and I'm taking advantage of the fact that edge illumination falloff is not perceptible in visual astronomy when the f/D ratio is low.
  • robotswantdata
    Very cool project. Been taking my dwarflab mini on hikes instead of the 12” dob ;) , not the same at all but enjoy getting dark sky and some great astro shots.
    • hebrox
      I want to start looking at the sky with my kids. Would be nice to have something portable like the dwarflab mini. How would you rate it? Does it capture planets in some detail?
      • robotswantdata
        Not good for planets IMO as 150mm focal length and a small 30mm aperture. Binoculars or small desktop DOB is better with kids for planets. The mini is amazing for deep sky objects for the price
  • oAlbe
    How does one get started in the telescope building hobby?
    • helij
      https://stellafane.org/tm/index.html has good guides. There are astronomy forums such as CloudyNights with their own ATM sections. Edmind Optics has All About Telescopes by Sam Brown available online - https://www.edmundoptics.com/ViewDocument/All%20About%20Tele...

      There are so many books around this and many great website such as this one for example: https://www.bbastrodesigns.com/tm.html

    • danilor
      I wanted to know as well! The resources I found, though, don't mention anything about what is the safety precautions one should take about the dust generated in the process. What masks to use and such. I understand everything should be done wet, but I wanted to know, for example, if one should wear a mask when polishing with cerium oxide even when wet. Maybe I'm being too cautions of this? I do fear what I don't understand! It's hard to make decisions without numbers. If anyone has any info on this please let me know! :)
    • hackingonempty
      You might be lucky enough that a local museum regularly hosts a telescope making workshop. In the SF Bay Area you can go to the Chabot Space & Science Center on Fridays 7-10pm.
  • hackingonempty
    Very nice!!

    What are you using for interferometry?