The Crab Nebula

L:R:G:B:Ha 315:285:285:285:270, LRGB subs at 15 minutes, binned 1X1. Ha subs 30 minutes, Binned 1X1

The Crab Nebula (catalogue designations M 1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. The nebula was first observed in 1731 by John Bevis, and corresponds to a bright supernova that was recorded by Chinese and Arab astronomers in 1054. Located at a distance of about 6,300 light years (2 kpc) from Earth, the nebula has a diameter of 11 ly (3.4 pc) and is expanding at a rate of about 1,500 kilometres per second.

At the center of the nebula lies the Crab Pulsar, a rotating neutron star, which emits pulses of radiation from gamma rays to radio waves with a spin rate of 30.2 times per second. The nebula was the first astronomical object identified with a historical supernova explosion.

The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and more recently, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula.

Processing:

Calibration, aligned and stacked each channel in Images Plus, RGB Color combine in Photoshop CS3. Processed the RGB image using Curves to stretch, Star bloat reduction process described by Neil Flemming, unsharp mask in conjuction with layer masking, and noise touch up with the Noise Ninja Plugin.

The Luminace data was similarily processed and then brought into the RGB image as a Luminousity layer in Photoshop. The Ha data was processed as the Luminance data, again brought into the LRGB image as a luminosity layer.

Reprocessed the data using a similar work flow, this time using the H-alpha data in place of the red (LHaGB), finally merging the two images in photoshop using layer masking to produce the final image. Cropped to cut the evident dithering on the edges of the image and reduced image size to 66%.