Hemisphere:  Northern  ·  Constellation: Cassiopeia (Cas)  ·  Contains:  The star 9Cas
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CTB-1 (Abel 85) - Faint Radio SNR in Cass, 


            Jon Rista
CTB-1 (Abel 85) - Faint Radio SNR in Cass
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CTB-1 (Abel 85) - Faint Radio SNR in Cass


Imaging Telescopes Or Lenses
Canon EF 600mm f/4 L II
Astrodon Tru-Balance 1.25" 3nm HA
Atik Electronic Filter Wheel EFW2
PixInsight PixInsinght · SharpCap 2.9
Guiding Cameras

Acquisition details

Sept. 8, 2016
Astrodon Tru-Balance 1.25" 3nm HA: 136x120" (4h 32') (gain: 200.00) -20C bin 1x1
4h 32'
Avg. Moon age:
6.50 days
Avg. Moon phase:
Bortle Dark-Sky Scale:
Mean SQM:

Basic astrometry details

Astrometry.net job: 1233880

RA center: 23h59m55s.2

DEC center: +62°2530

Pixel scale: 2.669 arcsec/pixel

Orientation: -89.176 degrees

Field radius: 1.006 degrees

Resolution: 620x450

Locations: Aurora South Backyard, Aurora, Colorado, United States


CTB-1 is one of the oldest objects on my list of things to image. I first became aware of it after Madratter posted his version on CN over a year ago (perhaps two years). I was fascinated with the object, because not only is it extremely faint and a true challenge to image, but it is also a Radio SNR, and emits resolvable structure in radio wavelengths. Such are the intriguing curiosities of the cosmos!

This image was both a bucket list object, as well as a test of my ASI1600MM-Cool. During early testing, many of us early adopters mused about the possibility of high gain short exposure narrow band imaging. In recent nights I've been experimenting with NB imaging at very high gain on this camera, with exposures as short as 45 seconds, although most are 90-120 seconds. The results have been nothing short of amazing. The high gain, low noise of this camera does wonders for narrow band imaging, and allows fairly deep integrations in less time than is usually required to get sufficient SNR to produce a reasonable image.

This particular image is 4h32m of exposure, 136x120s, Gain 200. Acquired with a Canon EF 600mm f/4 L II lens, using SharpCap for acquisition and control. Total time spent acquiring data was a little over 5h30m. The skies were horrid when I acquired this data...some of the worst transparency I've seen, on top of being in a red zone and having a half moon in the sky. I am hoping to take another crack at this guy once the new moon sets in, preferably on a night of much better transparency.



  • CTB-1 (Abel 85) - Faint Radio SNR in Cass, 


            Jon Rista
  • Final
    CTB-1 (Abel 85) - Faint Radio SNR in Cass, 


            Jon Rista

Sky plot

Sky plot


CTB-1 (Abel 85) - Faint Radio SNR in Cass, 


            Jon Rista