I have had a 10-inch Starfinder sitting unused for years, and am now for the first time trying to set it up correctly. It produces good results on deep sky subjects with a 24-inch Konig, but planets look consistently fuzzy with higher-power eyepieces (say 7mm UO Ortho). Even a little fuzzy with 15mm Panoptic.
I have a Ronchi grating (which i think came from Coulter, years back) but I can not make sense of the instructions.

So... I know this is a bonehead question, so I hope i am asking it in the right forum. How the heck do i use this little Ronchi screen to check out the optics on the Starfinder??

Thanks in advance

Bob