M33 - The Pinwheel Galaxy

Spiral Galaxy in Triangulum

Uploaded 12/3/05

Select an image size for a larger view: 800 x 600 (smallish) 1200 x 800 (getting there) 1600 x 1200 (Best!)

 How does one begin to describe such an incredible object in mere words? This image of the Pinwheel Galaxy is my deepest image yet of this splendor, and from an image processing standpoint required developing some all new techniques. The last time I shot this galaxy with a CCD was in 2001 and used my ST7E. Now lets get down to the details:

The Galaxy

Located in a relatively star poor constellation, M33 has an integrated photographic magnitude of 6.3, but is spread out over a degree of sky, and thus is low surface brightness. Despite this, it is a very easy naked eye object on any clear night, when Triangulum rides high in the fall and early winter skies. An interesting fact is that the B-V index is .55, which is getting quite reddish. You can see in my image above why that would be the case, the entire galaxy is covered with an enormous amount of red hydrogen (HII regions), and the blue part of the arms does not really start until a fair distance out from the center, thus the more yellow core is the dominant light source here. This galaxy actually has a measurable inclination, of about 4 degrees and is classed as an SA(s)cd galaxy.

There are literally hundreds of reddish - pink HII regions in this image. While most atlases identify maybe half a dozen of the more prominent ones, Simbad and the Aladin online Atlas has thousands of objects. Look closely and you will see that a majority of them surround blue stars and associations. When I first put this image together, I couldnt believe how many HII regions contained the source of thier illumination, mostly hot O/B stars and clusters. I invite you to explore the largest image and take in the knots, faint tendrils and wreaths of nebulosity, and countless resolved blue supergiants here seen in another galaxy.


2 hours of unfiltered Luminance data (IR included), and one hour of H-alpha data were combined to make a detailed L channel. This was combined with one hour of RGB data in Photoshop using layers, with the RGB layer set to "color". The H-alpha data was next processed separately, and the stars removed by subtracting the blue channel. The color was added by using the color of the brightest nebulosities in the RGB data to tint the image. Next, this final H-alpha only image was layered in PS with the LRGB created earlier and combined with Lighten.

Instrument: 12.5" f/5 Home made Newtonian Platform: Astrophysics 1200 QMD CCD Camera: SBIG 10XME NABG with Enhanced Cooling Guider: SBIG ST4 Exposure: HaLRGB = 60:170:20:20:20 (RGB Binned 2x2) RGB Combine Ratio: 1: 1.05: 1.11 Filters: AstroDon RGB Tricolor, H-Alpha, Clear Location: Payson, Arizona Elevation: 5150 ft. Sky: Seeing FWHM = 6.5 arcsec (Maxim DL - 10min subframe), Transparency 8/10 Outside Temperature: 40 F CCD Temperature: -30 C Processing Tools: Maxim DL, Photoshop, PixInsight, CCDOps Debloomer. HOME GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS


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