3D-printed Newtonian Reflector Telescope

With this 3D-printed telescope, you can enjoy the wonder of space from your backyard. This is the 2nd iteration of my Newtonian Reflector Telescope, with a 6" primary mirror and a 750mm focal length. I have affectionately named this one Newton To See Here.

What's a Newtonian telescope?

A Newtonian telescope is a type of Reflector telescope invented by Sir Isaac Newton in or around 1668. This type of telescope is popular with amateur and DIY telescope makers because it is relatively easy to construct and is generally less expensive than comparable quality/size telescopes of other types. As a bonus, the views it produces are amazing!

You can read more about this telescope in this article I recently published.

Supplies

Almost everything is 3D-printed and can be downloaded from www.BigBigSpace.com. But, the two mirrors and the eyepiece (focuser) are not 3D-printed. You’ll have to purchase the mirrors or source them from a refurbished or discarded telescope. I purchased my mirrors new from AngenaAstro.com. This one is guaranteed to fit the dimensions of the telescope, and has the proper focal length (750mm) for the truss tube design in this project.

Additionally, you'll need 8 truss tubes. For strength and to keep it light-weight, I purchased carbon fiber tubes from Amazon.com (sold in pairs). You can substitute extruded aluminum tubes if you want to save a few bucks. Each tube must be 15mm in diameter (outer) and 480mm in length.

Step 1: Download the STL And/or Fusion 360 Files

To begin, download the provided STL files from www.BigBigSpace.com. We've also provided a Fusion 360 archive file that you can use if you want to customize any of the parts. The largest part (the primary mirror box) is approximately 240mm x 240mm. Make sure your printer can accommodate this size.

Start printing!

Step 2: Assemble the Primary Mirror Cell

The Primary Mirror cell holds -- you guessed it -- the primary mirror. As it turns out, the primary mirror requires very careful placement and alignment. The primary mirror cell's job is to make sure the mirror has proper plate and edge support.

Print the items below. All are provided in the STL files.

1. Primary Mirror Cell (1)
2. Edge Support Thumb Screws (9)
3. Mirror Clips (3)

Assemble the parts as shown. If you don't have a mirror yet, you can insert it later.

Step 3: Print and Assemble the Primary Mirror Box

The Primary Mirror Cell from the previous step will be housed in the Primary Mirror Box (PMB). The PMB protects the mirror and also has connectors for the truss tubes and the altitude bearings (more on that soon).

The is the largest item to be printed. It requires a build plate that is at least 240mm x 240mm. If your printer is not large enough, you can cut the box into two or four parts, then screw them together. On my printer, this piece took about 30 hours to print!

Once printed, place the Primary Mirror cell into the box. You'll see three curved retainer walls that will hold the cell in place.

Orientation:

Note that the mirror cell has three walls protecting the edge of the mirror. Two of the walls are closer together than the other. These two walls should be towards the side of the mirror box that will support the mirror when tilted. Think of it this way: when you tilt the telescope towards the horizon, the mirror will need to be supported along the side edge. That edge should be supported by the two closer edge walls.

Step 4: Upper Optical Assembly

Print and assemble the Upper Optical Assembly (UOA). This will hold our secondary mirror cell and the focuser. You'll need some screws and nuts for this. I used #10-32 / 1" screws (24) and #10-32 nuts (24).

Printable parts in this assembly include:

1. Lower rib (ring)
2. Upper rib (ring)
3. General Supports (3)
4. Focuser Support (1)

Note that the focuser support is designed for a Crayford-style focuser with a flat base and four 72mm (center-to-center) screws. Your focuser might be different. If so, you can design and print your own focuser support -- everything else will work as is.

Step 5: Attach Secondary Mirror Cell

The secondary mirror cell hangs down from the Upper Optical Assembly. It attaches to the top with a 40 M6 40mm thumb screw and a barrel nut. You can also add three socket head screws at the top to help with collimation.

To attach the secondary mirror to the cell, use a dollop of two-part epoxy. Insert the dollop into the recessed portion of the surface cut at a 45 degree angle. That way the epoxy will spread out when compressed but the mirror will stay flush with the non-recessed surface.

Step 6: Attach Truss Tubes

Print the truss tube connectors (8 of them) and insert them into one end of the purchased truss tubes. As noted earlier, you'll need to buy 8 tubes. I recommend the carbon fiber tubes found on Amazon. The tubes must be 480mm in length (the ones on Amazon are 500mm, so I cut off 20mm from each).

Insert the opposite end of each tube into the mirror box. Then attach the tubes to the upper optical assembly using M6 x 25mm Thread Thumb Screws.

Step 7: Altitude Bearings

The Altitude Bearings allow you to tilt the telescope up (to the zenith) and down (to the horizon). These are large and therefore need to be printed in 3 parts each. You can assemble them with two #10-32 / 1" screws + nuts at each joint. Finally, you can attach the assembled bearings to the primary mirror box using 4 M6 40mm Thread Thumb Screws.

Step 8: You're Done!

Here's a quick assembly video. If you'd like to learn more about this telescope and its design, read this article and visit the telescope's website.

Step 9: Enjoy the Views!

The views are incredible! Here are a few of my favorite Moon photos, taken with this telescope connected to an iPhone 11 Pro.

Comments

[Hadjipavlis]

I am sorry for my ignorance, seriously considering in making this telescope. I need to know to start with if by making https://www.thingiverse.com/thing:4705423 , Crayford Focuser 2inch as it shows no lenses, if this the case, or i will need some lenses for the focuser.

[joedude]

A friend recently got me interested in Astro photography. Can’t wait to get printing this! I already have full frame DSLR and mirrorless cameras. Is there a camera mount that is compatible with this telescope?

[rfiol]

Yes! I connected my Nikon DSLR to this telescope (actually really depends on the focuser you choose for the telescope, not the telescope itself). I purchased a T-Ring connector and it worked great *BUT* you will probably need to add a Barlow lens since the camera's focal point may be different that the eyepiece's focal point.

Here's my camera connected to this telescope:

[joedude]

Very cool! Thanks for the reply! I’ll look into a Barlow lens

[Legsmaniac]

I would have loved to build this with new Crealty Ender 3 printer coming on Christmas Day but sadly it's 220mm sq. - 20mm short of requirement for this project. 😒
I see too many projects here on Instructables that are too large for most general hobby printers. Such a shame. So sad.

[PjS13]

Take the fusion 360 file and break the part down into 4 smaller parts like he recommends doing in this instructable.

[rfiol]

I can sympathize. I had a small printer up until recently. So, I plan to update the project to include a version whereby the larger parts (mirror box, etc) are cut into multiple parts, which can be assembled together. If you know Fusion 360, I've provided the Fusion files so that you can do this yourself.

[Legsmaniac]

Hi and thank you for your kind reply. I would certainly be VERY interested if the project is adapted to allow for smaller interlocking parts so I would very much look forward to this if and when you do update it. Being very new to 3D printing (only getting my first ever 3D printer on Xmas Day!) I have yet to investigate and learn programs like Fusion 360 so I very much doubt I'll be able to adapt the project myself any time soon, sadly. I only wish all other Instructable posters would consider smaller parts adaptations for those of us with smaller printers as a matter of routine.
If you ever do adapt the project, please do let me know. And thank you so much.

[netcareca]

Wonderful project - congratulations! Any chance to adapt files for a 6 inch F/8 primary mirror? Please give me hope... Thanks for this great instructable!

[olanderd]

I just finished this using the 6" f/5 that was recommended but adapting the files to an f/8 wouldn't be hard to do. You would have to change the angle of the support tube holes on the primary mirror housing and then change the angle on the truss supports at the other end. You'd also have to change the length of your support tubes to about double the length, but you'd want to run the math to get the exact length. Good luck it was a fun project and well worth the effort.

[SwaglessHombre]

Super cool project! Quick question for comparison: Do you happen to know, if I were to purchase an equivalent telescope from a Commercial brand how much do you think I'd have to pay 😅?

[olanderd]

I have my printers in overdrive trying to get this ready for Christmas. My wife has always been fascinated with the stars and spends countless hours looking up at them on clear nights. This is going to be a great present. Thank you for putting this Instructable together. I'm going to order the mirrors and focuser that you've recommended but it looks like I'll also need to get an eyepiece. What do you recommend? There are so many options, I'm a complete NOOB when it comes to telescopes, but I love to make things.

Also, what basic settings did you use for your 3D prints? Wall thickness, top and bottom thickness, infill %, layer height, etc.?

[rfiol]

I am so excited to hear that you're printing this telescope. Please promise to contact me and share your results. With regard to the focuser, I purchased this one:
https://agenaastro.com/gso-crayford-focuser-reflec...
Be sure to get the flat base plate option. It's a great focuser for a reasonable price.

For printing, I used 15% infill and 4 top/bottom solid layers. Pretty much everything else I left a default settings. The telescope is pretty light overall. Enjoy!

[olanderd]

Thanks for the info on the printing.

As for the focuser, that is the one I got. I was curious about the eyepiece though. It seems that I have to purchase one of those as well and there are options for both 2" and 1.25" and this focuser can handle both. I just have no idea which one I should get.

I will share with you when complete. I think she is going to love it.

[rfiol]

I can't wait to see it completed! I just got some great pics of the conjunction with mine. Worked great!

[olanderd]

That's great. I've got my central mirror epoxied and drying at the moment. the carbon fiber tubes are supposed to be here tomorrow. That's the last thing I need to finish this up. And also to get the focuser mounted. It's coming together nicely though. Thanks again for sharing.

[rfiol]

Fantastic! I also recommend you get one of these. This will help you to make sure your mirrors are aligned perfectly.
https://www.amazon.com/gp/product/B00LX34ZH2/ref=p...

If you're not familiar with the process, Google "reflector telescope collimation", or check out this video:

[RichardGreene]

Way cool!
I'm curious how you were able to put the separately printed parts of the altitude bearings together. The Fusion file looks like it assumes a perfect fit at those lap joints in order for the screw holes to align (and their diameter is also a bit small for #10 screws). In the assembly video, are you using your drill driver force the screws to ignore any mismatch due to printing tolerances? Or did you maybe sand the parts to fit perfectly first?

[olanderd]

I'm in the process of building this right now. I have the last couple pieces on the printer right now. I've had to drill out all the #10s. if you're going to print this a couple things that I would recommend that I had problems with. Make sure all the printed screws are solid from where they attach to the head up and two or three layers below. Everyone of mine snapped off at the first go around with a 15% infill. Also all the #10 connections have tapered holes. I would change one sideof each connection so that it had a nut recess. This would allow you to have 3/4 in screws instead of one inch screws which would keep them from protruding. Besides that I really haven't had any issues with fit. I'm still waiting for all the parts to get here though. But I think I'm going to be good.

[rfiol]

Regarding the alt bearings, I used the push-pull tool in Fusion to add a .25mm clearance on the lap joints. That tolerance is include in the STL files on the site. With my printer, that worked out perfectly. I had no mismatch issues with any of the joints. In the video, I used a drill because I am lazy. :).