Whirlpool galaxy thru a 12” Dobsonian?

[FLO]

Somebody asked me today:

When viewing the Whirlpool galaxy (M51) thru a 12” Dobsonian, how much detail should he expect to see?

[Astroman]

As always, it depends on your skies. That said, under fairly dark, clear skies, you should easily see structure in the spiral arms of M51 and the satellite galaxy, Ngc 5195. Under really dark skies, you should see individual clumps in individual spiral arms of M51, plus the "bridge" between the two, which is made up of two slightly brighter arms and a dark dust lane between.