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CTB-1 (Abell 85) Supernova Remnant (Starless)

Technical card

Resolution: 2272x2842

Dates:Aug. 13, 2018Aug. 23, 2018Sept. 3, 2018

Astrodon Ha 5nm: 216x240" (gain: 139.00) -20C bin 1x1
Astrodon Ha 5nm: 332x120" (gain: 201.00) -20C bin 1x1
Astrodon OIII 3nm: 733x120" (gain: 201.00) -20C bin 1x1

Integration: 49.9 hours

Darks: ~50

Flats: ~50

Bias: ~250

Avg. Moon age: 12.34 days

Avg. Moon phase: 48.06%

Bortle Dark-Sky Scale: 6.00 job: 2689192

Locations: Backyard Red Zone Observatory, Taylor, MI, Michigan, United States

Data source: Backyard


I don't believe all deep space images look good starless, but in this particular case there was a lot of background Ha partially obscured by a pretty thick star field. Unfortunately I had to reprocess everything all over gain, as I had originally ran deconvolution in PixInsight. Nikita's StarNet++ does not work so well with deconvoluted images due to the variations in how each person handles the process. So despite how well StarNet++ works, in my case it took some time.

CTB1 is a nearby supernova remnant (SNR) with an apparent diameter of about a half a degree (about the same size as a Full Moon). Upon early discovery, CTB1 was thought to be a planetary nebula, so Abell included it in his catalog of planetary nebulae as Abell 85. It was identified as a SNR by van den Bergh et al. in 1972 based upon its optical half-circular shape consisting of radiative filaments. Deeper images taken in H-alpha by Fesen (1993) show that it has a complete circular shape except for the unusual breakout structure toward the northeast, which also shows up in X-Ray images. Distance and age estimates are 10,000 light years, and 7,500 – 11,000 years, respectively. It spans nearly 100 light years.



Douglas J Struble
License: None (All rights reserved)


CTB-1 (Abell 85) Supernova Remnant (Starless), 


            Douglas J Struble