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beamsplitter no astigmatism!???
I set up the OAG with the beamsplitter on the ED80 and used my old focault tester and a Ronchi screen.
No visible astigmatism....
My beam splitter is only 0.7mm thick. I can only suggest if you were using a very thick beamsplitter and maybe it was being "bent" in the holding device you might see a problem, but I think for general use it works well.
If you have a good OAG in the first place, there's really no need for a beamsplitter. I only use mine due to the difficulty of positioning ( and keeping) a star image on a 20 micron wide slit.
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