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Monday, January 11, 2016

Abell 85 (CTB1), a dim Galactic Supernova Remnant in Cassiopeia, project finalized

I started this imaging project at January 2015. This January 2016 I was able to shoot more exposures for this dim target to finalized my imaging project. It's always a pleasure to have the image ready after a long period of time. As usually, I compared my exposures from different years to see has anything happened up there during the year. Usually there are no difference other than seeing conditions but this time I spotted a suspected variable star in the image field. (NSV 26187) There is an animated image in this post to show the difference between the years 2015 and 2016. 

Abell 85 (CTB1) 
SNR G116.9+00.1 in constellation Cassiopeia, click for a large image.

Image spans about one degree of sky. The photo is in mapped colors from the light 
emitted by an ionized elements, red=sulfur, green=hydrogen and blue=oxygen.

Abell 85 in visual colors
Please, click for a large image

Natural color composition from the emission of ionized elements, R=80%Hydrogen+20%Sulfur, G=100%Oxygen and B=85%Oxygen+15%Hydrogen to compensate otherwise missing H-beta emission. This composition is very close to a visual spectrum.


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.

Suspected variable star

An animated image showing a suspected variable star, NSV 26187, brightness variation between the years 2015 and 2016.

Technical details

Processing work flow

Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 21 iterations, added at 25% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Celestron Edge HD 1100 @ f7 with 0,7 focal reducer for Edge HD 1100 telescope

10-micron 1000

Cameras and filters
Imaging camera Apogee Alta U16 and Apogee seven slot filter wheel
Guider camera, Lodestar x2 and SXV-AOL

Astrodon filter, 5nm H-alpha
Astrodon filter, 3nm O-III
Astrodon filter, 3nm S-II

Exposure times
H-alpha, 21 x 1200s =7h
O-III, 9 x 1200s binned = 3h
S-II,  6 x 1200s binned = 2h
Total 12h

A single uncropped, calibrated and stretched 20 min. H-alpha frame as it comes from the camera

This really is a dim target...

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