M33 - The Triangulum Galaxy - 2015 version
M33 - The Triangulum Galaxy - 2015 version
M33 - The Triangulum Galaxy - 2015 version
M33 is the third largest galaxy in our Local Group of galaxies which includes M31 (the Andromeda Galaxy), and our own Milky Way Galaxy. Visually, the galaxy is quite large - about 70' x 40'. This makes the galaxy about 3 times larger than the Full Moon. However, unlike the Full Moon, M33 has a very low surface brightness, so it is quite challenging to see as well as to photograph.

The Triangulum Galaxy has many HII (Hydrogen Gas) regions. In this picture, you can see these HII regions as the magenta colored areas. Similar to the Orion Nebula and Lagoon Nebula, these regions are areas of star formation. Many of these HII regions are identified in the annotated version of this image along with over 20 background galaxies.

In this image, North is to the Left. This image is cropped to 52% of the original full frame.

Exposure Details
Lens Nikon 600mm f/4 ED IF
Focal Length 600mm
Focal Ratio f/6
Mount Schaefer GEM - 7 1/2 Byers gear
Guiding William Optics 50mm guide scope, Lodestar autoguider, PHD Guiding
Camera Hutech modified Canon 6D
Exposure 174 RGB subexposures of 300 sec at ISO 1600 (14 1/2 hrs) plus 154 Ha subs of 600 sec at ISO 1600 (25 2/3 hrs) - 40+ hours of total exposure
Calibration 30 darks, 30 flats, 30 bias
Date 10/9, 10/10, 10/11, 10/20, 10/30, and 10/31/2015
Temperature 67F on 10/9, 60F on 10/10 and 10/11, 48F on 10/20, 56F on 10/30 and 10/31
SQM Reading 21.35 (Bortle 4) on 10/9, 10/10, 10/11, 21.20 (Bortle 4) on 10/20, 21.15 (Bortle 4) on 10/30 and 10/31 (brighter when Moon was up)
Seeing 3 of 5 on 10/9, 10/11, and 10/30; 4 of 5 on 10/10, 10/20 and 10/31
Location Pine Mountain Club, California
Software Used Images Plus 5.75 for camera control. Images Plus 6.0.5 for calibration, stacking, ArcSinH stretching, star size reduction, smoothing and noise reduction, vertical band suppression, adaptive Lucy-Richardson restoration, color channel splitting and recombination. Photoshop CS5 used for levels and curves, screen mask invert, high pass filter, lab color, saturation adjustments, selective color, and match color. Gradient Xterminator for gradient removal. Carboni Tools for additional noise reduction and smoothing. HLVG for additional color correction. Registar 64 for subexposure alignment and color channel alignment. Pixinsight 1.8 for multiscale median transformation and morphological transformation.
Notes This is the third time I've imaged this beautiful galaxy. The good news is that I feel it is improving with each new version, so at least my efforts aren't for naught! In my second try at M33, I had added Ha data to fill in the colorful HII regions. While I did the same thing with this version, I have learned better how to control this process, so I ended up with a very good representation of these star forming regions. All in all, I'm very happy with how this image looks.

If you liked this picture, you might also want to view:

SUPERCEDED-NEWER VERSION AVAILABLE---M33 - The Triangulum Galaxy - 2011 version

SUPERCEDED-NEWER VERSION AVAILABLE---M33 - The Triangulum Galaxy - 2012 version