IC5146 “Cocoon Nebula”May 17, 2020
HaLRB image taken on 2016 with the GSO Telescope and the ATIK-One camera. Ha:14×900, L:10×900, R &B 6×600 each. Total exposition time 8 hr 20 min.
IC 5146 (also Caldwell 19, Sh 2-125, and the Cocoon Nebula) is a reflection/emission nebula in the constellation Cygnus. The NGC description refers to IC 5146 as an open cluster of 9.5 mag stars involved in a bright and dark nebula. The cluster is also known as Collinder 470. It shines at magnitude +10.0/+9.3/+7.2. It is located near the naked-eye star Pi Cygni, the open cluster NGC 7209 in Lacerta, and the bright open cluster M39. The cluster is about 4,000 ly away, and the central star that lights it formed about 100,000 years ago; the nebula is about 12 arcmins across, which is equivalent to a span of 15 light years.
When viewing IC 5146, dark nebula Barnard 168 (B168) is an inseparable part of the experience, forming a dark lane that surrounds the cluster and projects westward forming the appearance of a trail behind the Cocoon.