Introduction: 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.


Almost everything is 3D-printed and can be downloaded from 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 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 (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 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.


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.

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