NGC 246 (PK 118-74.1)
FS-128 (ag, ST-4)
ST-2000XM LRGB 5 minute subs
NGC 246 is a bi-polar pulsating planetary with ~72 minute pulsation rate.
A cavity within the nebula and an outer envelope shield the planetary from the
ISM resulting in cool photo ionization of planetary material. (Hoogerwerf,
et.al. - 2007)