Here is link about using a LED to build an artificial star, it does not seem to require more than about 100 ft of distance.
http://observatory.mvastro.org/library/Star_Test/ArtStar.html On 10/18/11, Hutchings, Mat (H USA) <mat.hutchings@siemens.com> wrote:
Aw, come on, you can brave the cold at night in the winter!
Yeah, to a point, but then again, I am designing a heated observatory, so that's gotta tell you something... ;)
Re: Ronchi testing
With much experience, you can tell a lot with the Ronchi test. I used to hang-out with a local optical manufacturer, and we'd look at mirrors through the Ronchi. I would point-out problems that he had to stare and stare at, and most of the time he'd say "yeah, maybe..." until we star-tested it. Then he'd admit that I detected it with the grid.
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