What is an Emission Nebula?
Emission nebula are clouds of high temperature ionized gas. Atoms are excited by high energy light from a nearby star and emit photons as they fall back to lower energy states.  Most emission nebula are red because Hydrogen is the most common gas. They emit light at the hydrogen alpha wavelength. These types of nebula are often the brightest of all nebulas and can be active star formation regions.
In these cases massive gas clouds collapse under their own weight, and then due to the conservation of angular momentum, begin to spin, flatten, and contract. Over a few million years, the temperature at the core with rise until it’s sufficient for nuclear fusion to occur and a star is born.
Good examples of emission nebula include the Orion nebula (M42), the Rosette nebula (Caldwell 49), and the Lagoon nebula (M8).
Crescent Nebula NGC6888
Celestron 9.25 SCT with Hyperstar
Heart Nebula IC1805
Skywatcher Esprit 100ED Refractor
Lagoon Nebula M8
Celestron C9.25SCT/Hyperstar
California Nebula NGC1499
Celestron C9.25/Hyperstar
Thor's Helmet NGC2359 in Narrowband
C9.25 with Hyperstar
Elephant's Trunk Nebula IC1396
C9.25 with Hyperstar
M78
Celestron C9.25/Hyperstar
IC2944 Running Chicken Nebula in Narrowband
Remote CDK24" Telescope in Chile
North America Nebula NGC7000
Celestron C9.25/Hyperstar
IC 5070 The Pelican Nebula
Celestron 9.25 SCT with Hyperstar
Orion Nebula M42
TEC140ED Refractor
Tulip Nebula
C9 Hyperstar
Eta Carina Nebula in Narrowband
Remote CDK24" Telescope in Chile
NGC2070 The Tarantula Nebula
Remote CDK24" Telescope in Chile
Trifid Nebula M20
TEC140ED Refractor
Running Man Nebula
TEC140ED Refractor
Lagoon & Trifid Nebula M8 & M20
Skywatcher Esprit 100ED Refractor
Elephant Trunk Nebula in RGB/HaOIIISII
RASC 16" Reflector
Heart Nebula IC1805 in Narrowband
Remote FSQ-106 Telescope in Australia
NGC3324 Nebula in Narrowband
Remote CDK24" Telescope in Chile
Rosette Nebula in Narrowband
Takahashi FSQ-106
M16 The Eagle Nebula in Narrowband
Remote CDK24" Telescope in Chile
Tadpole Nebula IC410
TEC140ED Refractor
Statue of Liberty Nebula in Narrowband
Remote CDK24" Telescope in Chile
NGC 6823
TEC 140
IC 63 Ghost of Cassiopeia
Celestron 9.25" SCT with Hyperstar
NGC 6888 Crescent Nebula in Narrowband
Takahashi FSQ106 in Narrowband
Soul Nebula IC1848
C9.25 with Hyperstar
NGC 6165 in Narrowband
Remote CDK24" Telescope in Chile
PacMan Nebula
TEC 140ED Refractor
North America Nebula
Radian 75 APO
Horsehead Nebula IC434
TEC140ED Refractor
Lobster Claw Nebula
C9.25 with Hyperstar
Bubble Nebula and M52 in Narrowband
Takahashi FSQ-106
Crescent Nebula NGC 6888 in Narrowband
CDK24 in Chile
Wizard Nebula NGC 7380
TEC140ED Refractor
Orion's Belt in Hydrogen Alpha
Takahashi FSQ-106
Tadpole Nebula IC410
Celestron 9.25 with Hyperstar
Monkey Head Nebula
Celestron 9.25 with Hyperstar
Seagull Nebula in HSO
Takahashi FSQ-106
Sadr Nebula
Celestron 9.25 with Hyperstar
Rim Nebula NGC 6188 in Narrowband
Takahashi FSQ-106
Central Orion nebulas
Ha modified Sony A7iii DSLR
Orion and Running Man Nebulae
Celestron C9.25/Hyperstar
Eta Carina Nebula
Remote Chile Telescope
Rosette Nebula
Remote telescope
Jellyfish Nebula IC443 in BGGR
Celestron C9.25 with Hyperstar
IC 1396
Remote Chile Telescope
M16 Eagle Nebula
TEC 160FL
NGC 6334 Cat's Paw Nebula
TEC 140ED
M17 Swan Nebula
TEC 140ED
Gum 65
Takahashi FSQ-106
SH2-119 Clamshell Nebula
Takahashi FSQ-106
CED214
Takahashi FSQ-106
Dolphin Head Nebula
C9.25/Hyperstar
North America and Pelican Nebulas
Sony A7iii DSLR with 150mm lens
Heart, Soul, Double Cluster
Sony A7iii/IRIX150mm
Orion Complex
Sony A7iii/IRIX 150mm
Flaming Star Nebula
C9.25/Hyperstar
Heart Nebula
C9.25/Hyperstar
Seagull Nebula
Sony A7iii/IRIX 150mm
Crescent Nebula
Radian 75 APO
M42/Running Man Nebulas
C9.25/Hyperstar
Thor's Helmet Nebula
C9.25/Hyperstar
Rosette Nebula
C9.25/Hyperstar
Running Chicken Nebula
Remote CDK24" Telescope in Chile
IC1314
C9.25/Hyperstar
IC1396
C9.25/Hyperstar
M16 Eagle nebula
TEC140
Seagull Nebula
Askar FRA400
Sagittarius Star Cloud
Sony A7iii
M20 nebula
C9.25 Hyperstar