This is a portion of the famous supernova remnant in Cygnus. It's a combination of long exposures through narrowband filters yielding a false-color image of the emission regions (red hydrogen, green sulfur, blue oxygen) with a conventional color image of the stars, calibrated for accuracy.

The dimmer nebulosity through the narrowband filters required 5-minute exposures at a high gain; the stars, 30-second ones at low. Just shy of 6 hours of integration time total.