DIY Telescope: Building a Foucault Tester

I’ve been polishing this mirror for a few weeks now and now that it’s completely polished out it’s time to start checking its shape. And to do this, I need to build a device known as a Foucault tester. Although it may look crude, this is actually an extremely sensitive contraption that can measure inaccuracies in the mirror of thousands of a centimeter #DIYTelescope #FoucaultTester #Telescopes