An Eagle and a Swan in HaRGB
An Eagle and a Swan in HaRGB
An Eagle and a Swan in HaRGB
Strattling the constellations of Sagittarius and Serpens, this widefield image features two beautiful emission nebulae, M16 (the Eagle Nebula) and M17 (the Swan Nebula). M16 is renowned for its beautiful Pillars of Creation that were made famous when the Hubble Space Telescope published its fascinating image of that region. Like M16, M17 is another region of active star formation. Also known as the Omega nebula, the Checkmark Nebula, and the Lobster Nebula, M17 is also the second brightest source of radio energy in the sky.

In this image, I blended 27 hours of Hydrogen Alpha data taken with a wide field 200mm lens along with detail images of M16 (8 hours) and M17 (13 3/4 hours) taken through my Celestron C8 at 1160mm. The detail images were RGB (color) images that I converted to greyscale and then layered into the H-alpha data. Then, I combined the enhanced Ha with 11 hours of RGB data of the wide field to create this HaRGB composite representing 60 hours of imaging.

In this image, North is to the left. This image is cropped to 83% of the original frame.

Exposure Details
Lens Canon EF 200mm f/2.8L II USM (Base image), Celestron C-8 w/Celestron focal reducer (M16/M17 detail images)
Focal Length 200mm for base image, 1160mm for M16/M17 detail images
Focal Ratio f/3.5 for base image, f/5.8 for M16/M17 detail images
Mount Schaefer GEM - 7 1/2 inch Byers gear
Guiding ONAG On-Axis Guider, Lodestar autoguider, PHD Guiding
Camera Canon 450D - Gary Honis modified (Baader Mod)
Exposure 160 x 600 sec @ ISO 1600 (26 2/3 hours) using Astronomik 6nm Ha clip filter + 131 x 300 RGB @ ISO 400 (11 hrs) for base image, 167 subs of 180 sec @ ISO 1600 (8+ hrs) for M16 detail image, 276 subs x 180 sec @ ISO 1600 (13 3/4 hrs) for M17 detail image
Calibration 30 darks, 30 flats, 30 flat darks, 30 bias
Date July 13, 14, 15, 16, 30, and July 31, 2013 for base images; May 16, 19, and 21, 2012 for M16 detail; June 24, 25, and 26, 2012 for M17 detail
Temperature 65F on 7/13, 62F on 7/14, 58F on 7/15, 7/16, and 7/30, 55F on 7/31
SQM Reading 21.35 (Bortle 4) on 7/15 and 7/16, 21.55 (Bortle 4) on 7/30 21.50 (Bortle 4) on 7/31
Seeing 4/5 on all 4 nights for base image
Location Pine Mountain Club, California
Software Used Images Plus 5.5 for camera control, calibration, stacking, and digital development. Images Plus 5.75 for feature mask, star masking, smoothing and noise reduction, and star shrinking. Photoshop CS5 used for levels and curves, hue/saturation colorizing, hue adjustments, lab color, selective color, high pass filter, and unsharp mask. Gradient Xterminator for gradient removal. Registar for registration and stack alignment. Carboni Tools for additional noise reduction and smoothing. Focus Magic for focus restoration. HLVG for additional color adjustment.
Notes I was very happy with my Ha image, but I had a lot of trouble trying to combine the Ha with the RGB color image. I had given up on it and was happy to have a beautiful greyscale Ha image. However, I let the data alone for a couple of weeks and then came back and took another stab at it. Eventually, I was able to combine the Ha and RGB and end up with colors with which I was happy.

I'm glad I gave it the second effort, as the resulting image looks pretty good to me. I guess the lesson I learned was that some times it pays to just walk away from the data for a little while.

This image won first place in's Easy-Widefield category for November 2013.

This image was published in the Fall 2014 issue of Amateur Astronomy Magazine in my article entitled "Processing Wide Field Images: The Taming of the Stars".