The Great Nebula in Orion, M42.
This image is a stack of 16 four minute exposures shot through a Hydrogen-alpha filter.
The exposures were acquired using an SXV-H9 CCD camera on a Tele Vue NP-101 4" refractor.
The exposures were calibrated, defect-corrected and stacked using AIP4WIN.
This image has been resampled down from its original size of 1392x1040.