CTB1 - Abell 85 (Luca Marinelli)

CTB1 - Abell 85

CTB 1 (Abell 85, SNR G116.9+0.1) is a faint supernova remnant in the constellation Cassiopeia. It was originally cataloged by George Abell as a planetary nebula as Abell 85 but was identified by van der Bergh, Marscher and Terzian in 1972 as a supernova remnant based on its appearance in the optical as an almost perfect half-circle of radiative filaments. CTB 1 is approximately 10,000 light years away and physically spans roughly 100 light years in diameter. It is dated to be ~7,500-11,000 years old. (Hailey and Craig, Astrophys. J. 434:635, 1994).

The brightest arcs of the hydrogen shell can barely be seen in a single exposure with my optical train, while the OIII signal is significantly fainter. This image was the result of one of the first datasets collected in my brand new backyard roll-off roof observatory. The ability to squeeze every minute of clear sky was crucial to generate quality data for this faint deep-sky object.

The acquisition is primarily bi-color narrowband (Ha and OIII) and star color is replaced from RGB data. Calibration, stacking, and linear processing of the data in Pixinsight, star separation with Starnet (PI plugin). Non-linear processing in Photoshop CC with denoising using Topaz Denoise AI.

Original
B
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D
E

B

Description: Slight curves adjustment.

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C

Description: Shrunk stars slightly to emphasize nebula.

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D

Description: Progressive buildup of signal to noise ratio as a function of number of subs used in the image integration process, from 1 to 292 subs in a small crop of the Ha channel.

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E

Description: Noise measured as the standard deviation of the signal in a small window of pure background sky as a function of number of subs in image integration. The square root dependence on number of subs is apparent.

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Status	Basic failed
Started	...
Astrometry.net job	4150757
PixInsight job	n/a
PixInsight queue size	n/a
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CTB1 - Abell 85

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