Telescope Optics Testing

This video covers the several different methods that can be used measure the shape of your telescope mirrors. It describes the underlying principles behind the null test along with the use of the Ronchi screen. It explains the conditions under which various mirror shapes will produce a null return. It defines spherical aberration and then studies how you can use it and a knife edge to reveal different characteristics about your mirror. It explores four tests that use a knife edge, or a variation of it, to measure the spherical aberration including: the Focault knife edge test, the Ronchi test, the wire test, and the caustic test. On the other hand, null tests provide the advantage of returning a single, immediate result. The video covers five null tests that are at the mirror makers disposal. It explains the Mobsby screen, the artificial star test, the Dall and Ross tests, the autocollimation test and finally the star test. By the end of this video, you will have a good understanding of the tests as they are being applied in the workshop.