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Getting plate-solving status, please wait...


            Gary Imm


Technical card

Resolution: 7860x5619

Dates:Dec. 2, 2018Dec. 3, 2018Dec. 4, 2018Dec. 18, 2018Dec. 28, 2018Dec. 29, 2018

Astrodon Blue 31mm Gen2 I-Series: 160x30" (gain: 139.00) -20C bin 1x1
Astrodon Green 31mm Gen2 I-Series: 160x30" (gain: 139.00) -20C bin 1x1
Astrodon Ha 31mm 5nm: 96x300" (gain: 300.00) -21C bin 1x1
Astrodon OIII 31mm 3nm: 96x300" (gain: 300.00) -20C bin 1x1
Astrodon Red 31mm Gen2 I-Series: 160x30" (gain: 139.00) -20C bin 1x1

Integration: 20.0 hours

Avg. Moon age: 21.83 days

Avg. Moon phase: 39.11% job: 2444595

RA center: 5h 40' 52"

DEC center: +28° 0' 0"

Pixel scale: 2.387 arcsec/pixel

Orientation: 0.772 degrees

Field radius: 3.203

Locations: Backyard (Mag 20.8 - New Moon), Onalaska, Texas, United States

Data source: Backyard


This object is a huge faint supernova remnant (SNR) located 3000 light years away in the constellations of Auriga and Taurus. The remnant has a span of 150 light years and an apparent diameter of approximately 3 degrees, filling an apparent area the equivalent of over 30 full moons.

I love supernova remnants! Although this huge object required a lot of imaging and processing as a narrowband four panel mosaic, I really wanted to see firsthand what this one looks like. The large scale filaments of this structure are amazing. Numerous irregular dark clouds somewhat obscure the nebula, particularly at the lower center and in the upper right quadrant. Some extended lobes are seen, which could be due to various factors such as non-uniform density of the interstellar medium, or non-symmetric expulsions from the explosion. A pulsar near the center of this nebula, not visible in this image, is the progenitor star. The bright red HII region to the lower left is Sh2-242.

The image captures hydrogen filaments in red and oxygen filaments in cyan, with hydrogen the much more dominant gas. Most of the other SNRs I have imaged have a more equal balance of hydrogen and oxygen. The IC 443 nebula (Jellyfish Nebula)) is one SNR which has a similar hydrogen dominance to SH2-240. Another similarity to the smaller IC 443 nebula is that the spherical nature of the SNR is still mostly intact in both nebula.

This object is also known as Simeis 147 (S147). This identifier was established in a paper by Gaze and Shajn in a Crimean journal in the 1950's. The name Simeis originates with an older astronomy facility operated by the Crimean Astrophysical Observatory in the city of Simeiz. The only other popular Simeis object is Simeis 57 (The Propeller, sometimes referred to as DWB 111).



Gary Imm
License: None (All rights reserved)

Sky plot

Sky plot




            Gary Imm