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Fleming's Triangle (Pickering's Triangle), 


            Kurt Zeppetello
Fleming's Triangle (Pickering's Triangle)

Fleming's Triangle (Pickering's Triangle)

Technical card

Resolution: 4598x3502

Dates:Oct. 8, 2019Oct. 14, 2019Oct. 16, 2019Oct. 18, 2019

ZWO B 1.25" optimized for ASI1600: 43x60" (gain: 139.00) -10C bin 1x1
ZWO G 1.25" optimized for ASI1600: 29x60" (gain: 139.00) -10C bin 1x1
ZWO Ha 7nm 1.25": 99x180" (gain: 139.00) -10C bin 1x1
ZWO O-III 7nm 1.25": 100x180" (gain: 139.00) -10C bin 1x1
ZWO R 1.25" optimized for ASI1600: 49x60" (gain: 139.00) -10C bin 1x1

Integration: 12.0 hours

Darks: ~12

Flats: ~15

Bias: ~20

Avg. Moon age: 15.39 days

Avg. Moon phase: 87.31%

Bortle Dark-Sky Scale: 5.00

Temperature: 13.00 job: 2997345

RA center: 20h 49' 38"

DEC center: +31° 34' 1"

Pixel scale: 1.204 arcsec/pixel

Orientation: 89.145 degrees

Field radius: 0.966

Data source: Backyard


This is the third part of the Cygnus Loop that I have imaged. The wispy clouds of hot gas and dust that make up this emission nebula are the result of a massive supernova explosion that occurred 5000 to 8000 years ago approximately 1500 light-years away in the constellation Cygnus. I have imaged Eastern Veil and Western Veil (Witches Broom), brightest and most popular parts of the Cygnus Loop, already and decided to try my luck with Fleming's Triangle (a.k.a. Pickering's Triangle) this time. It was discovered photographically in 1904 by Williamina Fleming at Harvard Observatory and originally named after Edward Charles Pickering who was director at the time.

I really love the wispy fibrous appearance of this whole area. I spent some pre-imaging time planning to frame it as I did not want to overlap with the Western Veil (Witches Broom) or Eastern Veil. It helped that this was the same orientation that I used when I was imaging the Pelican. I also wanted to get the luminous knots NGC 6979 and NGC 6974 located on the lower part of the image discovered by Lord Rosse (6974) and by William Herschel (6979). The designation NGC 6979 is often used to refer to Fleming’s Triangle. I managed to get over 11 hrs of total exposure over 11 nights imaging after the Pelican went behind some trees. Some more productive than others - one night invisible wispy clouds and another night the equipment gods abandoned me so nothing worked - fortunately they returned the next night. I enjoyed processing this image and I did have to get rid of a couple blown out star halos which I will post a video on in the near future. On that same line, the nebula was done with Hydrogen and Oxygen filters but the stars were composed of RGB data. I used a simple method of combining the star data in PixInsight - thanks Gary Imm!

Lastly, the first image is a typical HOO where Ha is in the red channel, OIII is in the green and blue channels. Just for giggles I did a second image where Ha is in the red channel, Ha and OIII are split 50-50 in the green channel, and OIII is in the blue channel. It gave a pretty neat looking color cast and I like the golden hue but I don't think it added any additional detail.

Imaging Dates: 9-16-19, 9-18-19, 9-21-19, 9-24-19, 9-25-19, 9-26-19, 9-27-19, 10-8-19, 10-14-19, 10-18-19



Kurt Zeppetello
License: None (All rights reserved)


  • Final
    Fleming's Triangle (Pickering's Triangle), 


            Kurt Zeppetello
  • Fleming's Triangle (Pickering's Triangle), 


            Kurt Zeppetello


Playing around with blends: Red - Ha 100%, G - Ha 50%, OIII 50%, B - 100%

Sky plot

Sky plot


Fleming's Triangle (Pickering's Triangle), 


            Kurt Zeppetello

In these public groups

Imaged with APT