NGC 6826 (also known as Caldwell 15) is a planetary nebula located in the constellation Cygnus. It is commonly referred to as the “blinking planetary”, although many other nebulae exhibit such “blinking”. When viewed through a small telescope, the brightness of the central star overwhelms the eye when viewed directly, obscuring the surrounding nebula. However, it can be viewed well using averted vision, which causes it to “blink” in and out of view as the observer’s eye wanders.
A distinctive feature of this nebula are the two bright patches on either side, which are known as Fast Low-Ionization Emission Regions, or FLIERS. They appear to be relatively young, moving outwards at supersonic speeds.
Content retrieved from: https://en.wikipedia.org/wiki/NGC_6826.