Hi Tony,
I think the 50x guide is reasonable and not quite in the hogwash category! I have had a few (and ONLY a few!) memorable nights with Jupiter at 400x in my 8" Dob...they were fantastic - good enough even for a half decent I-phone 5 photo! But mostly, 200x is much more pleasing...that's with Jupiter...not every planet, DSO is the same of course, but I find my 6mm EP is lovely for Jupiter, Saturn, Uranus and Venus...and the Moon of course! Sometimes I'm very naughty with the moon and up the mag to 800x...and yes, on those rare occasions, it looks great! But then I peg it back to 200x and you know what? More pleasing than a great big 800x moon 99% of the time! I guess the answer then is, just experiment and take it night by night! I usually use my 6mm EP and my 32 because they cover most bases and are decent EP's. My others come out on rare occasions!
Keep pointing up!
