Abell 21 – that’s how Medusa Nebula is named in the planetary nebulaes catalog created by George O. Abell. It is quite old nebula, already pretty diffused in the interstellar medium.
The piture below has been shot at the end of the year 2015. It is total a little bit over 10 hours of exposures, most of them made in the hydrogen alpha filter. Plus 3h of oxygen signal, and 2 hours of total RGB. Made with TS 130/910 0.79x refractor and Atik383 camera on EQ6 mount.
In the upper right part of the frame there is loose open cluster – NGC2395. And when you enlarge the picture there is small blueish star in the nebula center. That is WD0017+283 white dwarf, that originated this nebula.
Here there is only hydrogen frames stacked, inverted and stretched. You can see the faint outer part of Abell 21. Kind of “tail” that nebula left behind traveling through interstellar medium.