The Crab Nebula

Enhanced Hydrogen Comparison

Super Nova Remnant in Taurus

Uploaded 1/21/09

Normal RGB Image (G2V) Select an image size for a larger view: 800 x 600 1290 x 960 1600 x 1200
Hydrogen Enhanced Image (G2V) Select an image size for a larger view: 800 x 600 1290 x 960 1600 x 1200

This pair of images represents the most detailed I've taken of this object so far with my 12.5" f/5 from Payson. Extreme care was taken to ensure a proper visual G2V color balance on both images. The technique will be discussed below.

The Object:

The Crab Nebula in Taurus is a super nova remnant that exploded in in the year 1084AD and has been rapidly expanding ever since. It is located a degree from the easternmost star in the Bulls horns, and glows dimly at a magnitude of 8.4. While small at 6 arc minutes, it is typical of the size of many galaxies in my telescope, and thus made a good target for my galaxy hydrogen enhancement technique. Look carefully at the lower left of this image, you will see a passing asteroid Anahita. It was 12.2 magnitude at this time, and was the 270th asteroid ever found.

The Colors in this Image:

The diffuse core of the Crab is produced by the light of high energy electrons and is called synchrotron radiation. It will photograph as nearly a continuum, white in color, sometimes with a very pale blue tint. Surrounding this core are the filaments of hydrogen, a pink hue extending over the entire nebula and beyond the inner core. The outermost edges, seen primarily on the left side of the right hand image has a bluish cast or rim. This is from OIII emission, with some H-Beta and Sulfur II light. The stars across the frame show the full spectral range, from deep red M stars to blue super giants.

Producing these images:

As most of you know, I am an extremist when it comes to doing my best to produce accurate colors as the eye might see them when imaging deep sky objects. The CCD filters were calibrated on several G2V sun like stars for producing a white image. Once this white point was set, most images will record with true coloration - with some offsets of coarse from emission lines falling near band stop edges. The LEFT image was a standard 2 hour Red, Blue, and Green set of exposures combined with the exact G2V ratios to produce a fairly accurate representation of the crab in visible light.

The image on the right is the same image with an additional 3 hours of hydrogen alpha light exposure data added in a very specific way. While the technique is detailed in my AIC article from last year, essentially it is to add the hydrogen data using screen to each color channel in a proportion of 100%, 8%, and 4% to the RGB. Then the MOST important part - I then re combine the original G2V color balanced RGB image over this hydrogen enhanced image using HUE. This fully restores that hard earned color balance to the nebula, the filaments and core. This technique allows the common astro imager to bring in new details that were previously hidden in the old RGB techniques. Now we can show much more than ever before in the nebulas faintest structures.

Instrument: 12.5" f/5 Home made Newtonian Mount: Astrophysics 1200 QMD CCD Camera: SBIG 10XME NABG with Enhanced Water Cooling Guider: Meade DSI Pro w/Lumicon Newt Easy Guider Exposure: RGB = 40:40:40 Ha+RGB = 170:40:40:40 AstroDon RGB Combine Ratio: 1: 1.05: 1.3 Location: Payson, Arizona, Elevation: 5150 ft. Sky: Seeing FWHM = 5 arcsec (Maxim DL - 10min subframe), Transparency 9/10 Outside Temperature: 35 F CCD Temperature: -30 C Image Processing Tools: Maxim DL: Calibration, deblooming (Starizona Debloomer), aligning, stacking Gralaks Sigma: Stacking PixInsight: Curves, Deconvolution, noise reduction Photoshop CS2: Curves, Color Correction, Gradient removal (Grad Xterminator), Cleanup HOME GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS