First light for a new Ronchi tester
One of the goals in improving my garage is to get back into building telescopes. I have a 12.5" f/5 Newtonian mirror that I just need to do some final figuring on which has been stalled for at least a decade, and I thought it would be great to get back into it. Step one would be to be able to test it properly. Over the years I've had an incredibly primitive Ronchi tester which was made from an old Radio Shack project box, some batteries and a bit of duct tape. But I hadn't managed to even find that one, and I would like to be able to test mirrors at home, without my weekly trip to the telescope makers workshop.
I had a 2D micrometer stage that I got years ago from Paul Zurakowsky, and thought that would make a great platform. I fired up OnShape to design a holder for the grating and a small prism. A little wiring to a small 4xAA battery box, and more time than was really necessary, and I had it done.
Pictured is the Ronchigram of a 6" aluminized mirror that I honestly don't remember how I acquired. It has an 88" radius, and appears that it might be slighly undercorrected. I suspect I looted it from a damaged telescope that I picked up at a garage or estate sale.
After I do some more cleaning in the garage, I'll dust off the 12.5" and remind myself what condition I left the mirror back in the day.
This picture was shot with my Canon T5i and a 75/300mm zoom lens, hand held. I also have constructed a small gantry that can hold a small machine vision camera that I can use to record images and snap them directly to my lapt..
I need to raise the level of the tester about six inches (my test stand is ridiculously high, but it does help keep my back from hurting).
Anyway, tiny bits of progress!