A very nice glowing gas bubble excited by a young hot star in its center, located in constellation Cassiopeia about 7500 light years away.

The star is member of young star cluster Stock 18, also in the center of the nebula partly obscured by darker dust clouds.
The names of the nebula arise from its appearance: it looks really like a minor version of the well not Rosetta Nebula and it is part of a much larger nebula structure which resembles in wide field images a huge cosmic question mark … with this nebula as the dot of the question mark.
Just right on top of this image there is another small faint nebula, Sh1-118 from the first Sharpless catalogue, classified as a planetary nebula and/or as HII region.
The first image is colored in some kind of Hubble palette (SHO), while the second image is more a HOO palette with the SII signal mixed to the red and green channels.
The colors of the stars are always natural RGB colors.

Borg 90FL
1.08 Flattener
ZWO OAG
ASI 2600MM Pro
ZWO EFW
Baader Ultra-Narrowband 3.5/4nm filters, Baader RGB filters
H: 36x300s
OIII:35x300s
SII:36x300s
R: 20x60s
G: 20x60s
B: 20x60s

Total Integration: 9h55m over 2 nights
Bortle 4-5, no moon

PixInsight