CTB1 “Supernova Remnant”May 17, 2020
This very difficult object is the result of the stacking of Ha 38 frames of 1800s exposition time each. The total exposition is 19 hr. The frame were taken with the FSQ telescope and the QHY90A CCD on July 2016.
This object is presently known as CTB 1. Previously it was cataloged as item 85 of the famous Abell catalog of planetary nebula (Abell 85). Recent research have discovered that CTB 1 (scientific designation G116.9+0.2) is actually a very faint supernova remnant, about the size of the full moon (33 arcmin). The hydrogen-alpha circular shell is extremely faint, and was just barely visible in a single 30-minute sub-exposure. For this reason the most used planetarium application don’t report its position in the Sky map and it must be located using the close NGC7788 open cluster on the left and the star 9Cas above it.
It is immersed in a dense cloud of ionised hydrogen and close in an area where several open cluster are present. In the left corner of the image below three of them are annoyed: NGC7788, NGC7790 and Harward 21.