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eyepiece query
I have a little celestron mak 90mm, fl=1200 f/13.3 that I have been using here in the inner city to look at the planets and some brighter binary stars. Anyway a celestron 43mm plossel I use gives crisp pinpoint stars but when I drop my newly purchased widescan III 13mm into it the stars get a little 'airy' type diffraction ring around them and lose all the crispness. The brighter the star the worse the effect. I focus and focus but it's there to stay. The planets look ok, I can get plenty of detail out of them, even Jupiter's moons look ok. But bright stars?Is this a mismatch of eyepiece and scope perhaps? Would worn or defective coatings on the EP cause this?Thank you for your opinions.
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