I dont see as eps are an issue really, my ep case is a motley lot.
Some plossls from Orion, one UO plossl, two celestron silver tops, a few kelners.Nothing high end trust me,lol.

more IMPORTANTLY the clear spot was probably very transparent, that helps a lot with M51, as Tony said above M51 with companion should have appeared as a bit more than point like,I see M51 as a rather easy to spot grayish round fuzzy,the companion is the same.

At no time time have I seen arms, or details mind you.
Just the grayish fuzzys.

Heres a link to another thread on M51 also here in the CN deep sky forum , in it youll find a drawing bye cloudy nights own Caol L, understand shes observing from a really dark sky, and has tons of experience.

http://tinyurl.com/npzc2q