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How to Make an Eight Inch Reflector Telescope: Introduction

This is Part 1 of 2 tutorials on how to make a telescope. And in this tutorial we make a generous 8 inch newtonian reflector.

(Part 2 on how to make the Cabinet Mount for the telescope is here)

A newtonian reflector is a simple design that is easy to make and it was invented by Sir Isaac Newton.

The 8 inch means that is the size of the mirror inside. And that is a good size mirror. This will give you some very rewarding views of objects in the night sky.

As we build this telescope I will go over the various aspects of telescopes. And I also have a video tutorial on making this scope. It is at the bottom of the page.

Will has a youtube channel with over 700 videos on projects you can make. Check it out right here




The telescope we make

This picture gives you a bit of an idea of the size of the telescope (in comparison to my arm). It is ten inches in diameter and it is twenty-nine inches in length.



An important bonus about this tutorial: This isn't just a step by step on how to make this exact telescope. I also explain to you the why of the making. This means that you will be able to use this build technique to make any size newtonian telescope. You don't have to have the same exact mirror that I have. You can have a smaller mirror or a large mirror and it can be of a different focal length.

Would you consider a donation of $1 to support my work? Paypal makes it very easy and safe. Click here to donate $1 - Every little bit helps Will to keep making great tutorials and projects. Thanks!



Parts List and Tools:

  • I have a more complete parts list including product links here
  • Purchased optical Parts: These are the four major optical parts you have to purchase
  • The remaining common parts:
  • 1 quart of fiberglass mix, this includes the resin and the hardener
  • 1 square yard of fiberglass cloth. I used very light weight. No need for heavy weight. That is for boat making. Light weight is sufficient and cheaper.
  • The tube - 10 inch quikrete tube that is 48 inches long (Quikrete Concrete Forming Tube 10 " Dia X 4 ' L)
  • 1 piece of 1/2 nch plywood 2'x2'
  • For the diagonal mirror:
  • 18 inches of threaded rod - 8-32
  • nine 8-32 nuts for the threaded rod
  • 1 piece of one inch diameter dowel that is 2 inches long
  • For the Mirror mount:
  • 3 brass flat head bolts that are 1/4-20 and 3 inches long (Brass is optional but they have to be flat head bolts
  • 3 1/4-20 wing nuts
  • 9 1/4-20 flat washers
  • 3 1/4-20 hex nuts
  • 3 springs that will slide over the 1/4-20 bolts. About 1 inch in length. You can get a bag of various springs cheap. Or you can get one long spring and cut it into three pieces.
  • 4 wood screws to attach the mirror mount to the tube (can vary in size)
  • For the Focuser:
  • 4 bolts that are one inch long and 6-32 thread
  • 4 nuts (6-32)
  • 4 flat washers (6-32)
  • 3 small pieces of sheet metal
  • 3 small pieces of cloth or velcro
  • Paint:
  • Flat black for inside of tube
  • Your choice of color for outside of tube. I chose red.

Tools, Drills etc

  • Saw to cut the tube and the wood with. You are going to need some kind of power saw to cut the disk circles. A jigsaw or bandsaw will be good for this.
  • A couple of screwdrivers for the various nuts and bolts
  • A couple of wrenches for the various nuts
  • 2 inch hole saw
  • Various drill bits to create clearance holes
  • A respirator, latex gloves and long sleeve shirt if you are going to fiberglass your telescope tube - The respirator will cost you about 25 dollars.


Overview of the Newtonian Reflector:

This shows us the telescope that we will make.

You can see the four major parts. They are the eight inch primary mirror, The smaller secondary mirror, the focuser/eyepiece and holding it all together is the tube. So the whole task is to figure out where these parts go in the tube and how to make them adjustable.


An important thing is that all these parts line up very accurately so we guide the light correctly and not lose any light. To do this we make the two mirrors adjustable. So, when we want touse the telescope we can adjust them so they are just right and then use the telescope. This is pretty easy to do. We build it so it is adjustable.

We could build it so everything was exactly secured in place. But that is a difficult challenge. We have to get the accuracy down to fractions of an inch. But the way we build it we can turn some screws and get it just right very easily.


The mirror mount

We build a mirror mount that holds the mirror on springs. You turn those wing nuts and it adjusts the mirror exactly as you need it.

The secondary mirror mount

And we can adjust the smaller secondary mirror with the threaded rods and nuts.


The focus point of a parabolic mirror

Ok, we need to figure a few things out when it comes to the mirror we use for the telescope. This is pretty easy. I will show you how.

There is an important thing about a telescope mirror. It is not flat. It is curved.

let's take a look at the light path bouncing off a mirror.


On the left you see a regular mirror. The light hits the surface and bounces straight back. But the telescope mirror on the right is different. The light bounces off and comes to a focus point. Every point on the mirror will direct the light rays to the focus point.


The mirror focal point

This focal point is important. It is the distance from the mirror surface to that focal point that we need to make our telescope. That focal point is where we put our eyepiece.

NextLet's continue and find the focal point of our telescope mirror



Watch the Video Here:



If you would prefer to buy an eight inch newtonian telescope like the one we build in this tutorial here is one on amazon. Or at least you can get a sense for what they cost:

Orion 9738 SkyView Pro 8-Inch Equatorial Reflector Telescope





Meade LX85 Newtonian Reflector Telescope, 8in, Optical Tube Assembly Only, 217022 (only the tube you see here. No tripod or stand)




See It with a Small Telescope: 101 Cosmic Wonders Including Planets, Moons, Comets, Galaxies, Nebulae, Star Clusters and More - Available in paperback and kindle on Amazon right here