How to visually tell the difference between a planetary nebula and a supernova remnant? If we see a nebula by looking through a powerful telescope, how can we tell whether we are looking at the remnant of a supernova or at a planetary nebula?
Thanks
A Supernova Remnant contains a Black Hole or a Neutron Star while a Planetary Nebula contains a White Dwarf. 

Also, Supernovae Remnants are likely to have great velocities, so Doppler is another plausible choice. - Not through telescope though.