The images in this gallery were taken using a Ha (hydrogen alpha) narrowband filter. This filter blocks all light except for a very small slice, centered at 656.3nm in the light spectrum (see the graph I've uploaded). Hydrogen alpha light is in the "red" part of the spectrum, and is very often seen in gas clouds associated with nebulae. The use of a narrowband filter makes it easy to image many types of nebulae from a suburban location, since all light pollution is completely blocked by the filter. With extended exposure times now possible very subtle details of the gas cloud can be imaged from my location. Notice the difference between the two images of M17, the Swan Nebula.
