This was my second target at the Golden State Star Party 2015. Despite three nights of clouds, rain, and thunder, I got a clear night!
This is frame two of my three pane mosaic of the m16/17 region.
Orion Sirius Mount
Orions SSAG and st80 guidescope
Hotech SCA Flattener (still doesn't do shit)
11 x 510" iso 1600
Processed in Pixinsight.
One of the things I learned using Pixinsight is star masks. Using the masks, I was able to knock the stars way back, allowing for the really quite faint Ha data to pop. Remember, the d5500 is non-modified, so the filter over the sensor blocks a lot of hydrogen alpha light.