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The completed mirror tester is working out wonderfully. It takes a little time to set it up just right, at twice the Focal Length (not pictured), but this is an invaluable tool for checking your telescope mirror for parabolization while fine grinding, polishing and figuring. You can find the original design at Stellafane Observatory.

Setting up the tester
Setting up the tester

The Rocky telescope was named after a very special puppy that has since passed on.

Completed Tester
Completed Tester

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Modifications to Stellafane's Telescope Mirror Tester


I like to re use materials whenever I can. Stellafane Observatory's excellent mirror tester had a fantastic knife edge tester viewing window design to follow, but I wanted to use a few things out of the recycle bin.


The holder for the razor blade was made out of plastic food containers, as were the impact panels (for a later post). I covered the holder in electrical tape to reduce any glare. I used the backing of a legal pad for the slider, along with a piece of 1/4" plywood and hex bolts painted black. In making it fully removeable, I can change out or remove the knife edge tester to clear the way for the Ronchi gram. Of course, I can also just slide it out of the way, but I like options. :)

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The H.O.G.


I was walking around in the tesseract, when I thought of a way to use up the extra wood from making the telescope mirror tester (will post next week). Here is the unfinished version of my H.O.G. Machine (Hands on Graphing). Saves paper! I can split the cubes up in many different ways using wood skewers. I have 3D printer version using biodegradable PLA in a foldable pocket size in the works.


Prime time! Deepest apologies, I had to.


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