Hemisphere:  Northern  ·  Constellation: Cassiopeia (Cas)  ·  Contains:  The star 9Cas
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CTB 1 (Abell 85) Supernova Remnant in Ha, 


            Mike Oates
CTB 1 (Abell 85) Supernova Remnant in Ha
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CTB 1 (Abell 85) Supernova Remnant in Ha

Technical card

Imaging telescopes or lenses: Takahashi FSQ-106 ED

Imaging cameras: Starlight Xpress SX-814 Trius Monochrome CCD

Guiding cameras: Starlight-XPress Lodestar Autoguider

Software: Sequence Generator Pro  ·  Photoshop CS6  ·  PIXINSIGHT 1.8

Filters: Ha 3nm

Accessory: Lakeside Astro Motor Focus System  ·  Starlight Xpress SX 'Maxi wheel'  ·  Starlight Instruments FTF3545B-A Focuser

Dates:Sept. 20, 2019

Frames:Ha 3nm: 42x1800"

Integration: 21.0 hours

Avg. Moon age: 20.56 days

Avg. Moon phase: 66.57%

Bortle Dark-Sky Scale: 8.00

Mean SQM: 18.32

Basic astrometry details

Astrometry.net job: 2936881

RA center: 23h 59' 42"

DEC center: +62° 28' 19"

Pixel scale: 1.434 arcsec/pixel

Orientation: 359.444 degrees

Field radius: 0.890 degrees

Resolution: 3414x2884

Locations: The Hills Observatory, Manchester, United Kingdom

Data source: Backyard


A very faint supernova remnant in the constellation of Cassiopeia. CTB1 was originally thought to be a planetary nebula and was given the name Abell 85. It is about the same size in the sky as the Moon.

Long exposure subs in Ha with Astrodon 3nm filter. The aim of this image was to show in detail the structure of the remnant. It also shows just how much Ha there is in the area.

Imaged over 5 nights from 12 - 20th Sept 2019 under Bortle 8 skies with an average SQM-L of 18.32 (averaged nightly readings of 18.0 - 18.55)

After processing another image to the north of this one (Sh2-170 (The Little Rosette) Nebula), I found that I was able to show fainter nebula, obtain lower noise and better contrast, so I re-processed this again from scratch.



  • CTB 1 (Abell 85) Supernova Remnant in Ha, 


            Mike Oates
  • Final
    CTB 1 (Abell 85) Supernova Remnant in Ha, 


            Mike Oates


Description: Complete re-process.

Uploaded: ...

Sky plot

Sky plot


CTB 1 (Abell 85) Supernova Remnant in Ha, 


            Mike Oates