M101 - The Pinwheel Galaxy
M101 - The Pinwheel Galaxy
M101 - The Pinwheel Galaxy
M101 is a large face on spiral galaxy that is about twice the size of our Milky Way Galaxy. This beautiful galaxy has a large number of H II regions - red hydrogen nebulae where star formation is taking place. In this image, one of M101's companion galaxies - NGC 5477 is easily visible in the upper left at about 10 o'clock.

In this photo, North is up. This image is cropped to 72% of the original full frame.

Exposure Details
Lens Celestron C-8 SCT with Celestron focal reducer
Focal Length 1160mm (measured from the image)
Focal Ratio f/5.8
Mount Schaefer GEM - 7 1/2
Guiding ONAG On-Axis Guider with PHD Guiding
Camera Canon 450D - Gary Honis modified
Exposure 192 subexposures of 180 seconds each at ISO 1600 - about 9 1/2 hours total
Calibration 30 darks, 30 flats, 30 bias
Date April 18, 2012 and April 22, 2012
Temperature 46F on 4/18, 57F on 4/22
SQM Reading 21.2 (Bortle 4) on 4/18, 21.4 (Bortle 4) on 4/22
Seeing 4 of 5 on both nights
Location Pine Mountain Club, California
Software Used Images Plus 4.5 for camera control, calibration, stacking, digital development, multiresolution sharpening, smoothing and noise reduction. Photoshop CS5 used for levels and curves, color balance, high pass filter, star shrinking, saturation adjustments, lab color, screen mask invert, and noise reduction. Gradient Xterminator for gradient removal. Carboni Tools for additional saturation adjustments, noise reduction, and smoothing. HLVG for additional color correction.
Notes I had imaged this object last year as the first object with my Canon 20Da. At the time, I was not autoguiding, so my subexposures were limited to 45 seconds. While my image last year turned out fairly nice, this year's version is much improved. Its satisfying for me to see clear evidence that my image acquisition and processing skills are advancing.

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