NGC 6818 -- Planetary Nebula in Sagittarius
The Little Gem (NGC 6818) is a tiny Planetary Nebula that resides 35 arcminutes north of
Barnard’s Galaxy (NGC 6822). Both are visible in the same low-power eyepiece field-of-view.
While low-power works best for Barnard’s Galaxy a much higher magnification is needed to
tease out details in the Little Gem.
The central stars (a binary system) are too dim for me to see in the little refractor, but the
inter-ring of the planetary nebula is doable at high magnification. An OIII filter did nothing to help
bring out additional details in the nebula (but did make it brighter). I found it not necessary to
use the nebula filter in the drawing. To me the ends of the ring appear thicker than the rest of the
loop. The inter-ring along the sides was very fleeting and difficult to confirm with certainty.
It is worth taking time studying the color of the nebula. I see it as a very pale blue-green. The
Little Gem is also called the “Green Mars Nebula” since the size of the nebula and Mars (at
opposition) are close. However, it was hard for me to call it green or to see, in anyway a
resemblance to Mars beyond size. I will stick to calling NGC 6818 the Little Gem.