You can see 11th mag stars with a 60mm refractor and easily with a 80mm refractor or binos.
A 6" newt will give you stars about 13th mag I believe depending on you visual accuity and seeing conditions
http://www.twcac.org/Tutorials/limit...tude_table.htm
http://www.go.ednet.ns.ca/~larry/astro/maglimit.html