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How to Make an Eight Inch Reflector
Part 8: finishing it and collimating it

In this part of the tutorial we finish off making the optical tube assembly and I show you how to collimate the telescope.

Collimating is the act of getting all the parts lined up so the image is correctly seen and to its best light gathering advantage.

Part 1 of this tutorial is here



install the mirror mount

Now you should install your mirror mount assembly with the mirror in it. Remember it goes into a position that is true to our focal length. In the case of my mirror and tube. The mirror surface should be 19.75 inches from the center of that diagonal mirror. If you need to review that math and calculation you can go back to part 4 here


How the collimation should look

Now everything is installed and ready to go. We just need to line up all the optical parts so they work correctly. This process is called collimating.

You collimate by looking in the focuser without an eyepiece installed.

And everything you see should be perfectly centered. This means the secondary is centered, the big mirror is centered and the reflection of the secondary on the big mirror is centered.


It is easy to collimate and you will get the hang of it quickly.

You do it by looking through the focuser and adjusting the wingnuts of the mirror and adjusting the threaded rods of the secondary. If you look through the focuser while you do this you will easily see how things move when you make adjustments.

turn wing nuts


 turn nuts

Get everything lined up and your telescope is ready to use! Congratulations.

Continue on (Part 2 on how to make the Cabinet Mount for the telescope is here) . That is where we make the stand for this telescope tube assembly.



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