NGC 6894 is a planetary nebula in Cygnus. It may be about 5.000 light-years distant. It was discovered by William Herschel on July 17, 1784. It is in the second H400 program. While many planetary nebulae are teal in color due to strong OIII emission this one is more red than teal. Whether this comes from H alpha or NII emission I don't know. They are very close emission lines and need a 3nm filter to separate these. Not having such narrow filters and not finding much in the literature I don't know the answer to this question. I'm going to guess it is both with NII being stronger but that is a pure guess with nothing to back it up.

Much longer exposures than mine show that it may be interacting with the interstellar medium. Gasses it emitted before the planetary nebula formed appear to have aligned with the magnetic field of the galaxy. If so this may help to understand the interstellar medium at least in this part of the galaxy.

This is another very early image that needs reprocessing if I ever find the time.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME