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Sunday, February 16, 2020

CTB1, a supernova remnant in Cassiopeia

This has been a very cloudy imaging season up here 65N. Last Friday we had about five hours for clear weather before the clouds rolled in. I managed to get just enough exposures for this dim supernova remnant in Cassiopeia. I have shot this target before with much longer focal length instrument. It's nice to see CTB1 in large context when imaging with Tokina AT-x 300mm f2.8 camera lens. 

CTB1 (Abell 85)
Please, click for a large image, it's worth it.

Image is in mapped colours, from the emission of ionized elements, R=Sulphur, G=Hydrogen and B=Oxygen. 

A closer look
Please, click for a large image

An older longer focal length image back from 2016
Please, click for a large image

More info about this photo here,


Abell 85 is a very faint supernova remnant in constellation Cassiopeia. It's difficult to image with any details due to extremely low surface brightness. Abell 85 has a largish diameter, about half a degree, it has a same apparent diameter as a full Moon. The physical diameter is about 98 light years across. This SNR locates about 9800 light years from the Earth. CTB1 was originally thought to be a planetary nebula and it was included the Abell catalog of planetary nebulae under a name Abell 85. It was confirmed to be a supernova remnant by Willis & Dickel at 1971.

Technical details

Processing workflow
Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 33 iterations, added at 50% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Tokina AT-x f2.8 camera lens

10-micron 1000

Cameras and filters
Imaging camera Apogee Alta U16 and Apogee seven slot filter wheel
Guider camera, Lodestar x 2 and an old spotting scope of Meade LX200
Astrodon filters,
5nm H-alpha 3nm S-II and 3nm O-III

Total exposure time
H-alpha, 9 x 1200 s, binned 1x1 = 3 h
O-III, 1x 1200 s, binned 2x2 = 20 min.
S-II, 1 x 1200 s. binned 2x2 = 20 min.

A single calibrated and stretched 20 min. H-alpha frame as it comes from the camera (Downscaled)

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