Gamma Cas Nebula

The Gamma Cas Nebulae complex, also known as Sharpless 2-185, is illuminated by the nearby star Gamma Cas and is about 190 parsec away from Earth.


recording data

object Sh 2-185
date of recording
August 5, 14 and 22, 2017
exposure 18.2 h, H-Alpha: 453x80", R: 607x20", G: 554x20", B: 298x20"
telescope Celestron RASA F2.2
focal lenght 620mm
filter Baader f/2 Highspeed 2" H-Alpha, Baader 2" R Filter, Baader 2" G Filter, Baader 2" B Filter
camera ZWO ASI1600mmc
gGuiding 250mm guide scope, MGEN
mount Celestron CGE pro
AstroBin click here

Cassiopeia's Ghost

IC63 (the bright, pointed object) and IC59 (the weaker object) are commonly called Sharpless 2-185 (Sh 2-185). Both are illuminated by the B0 IV star Gamma Cas. Both nebulae are near this ionizing star, but have very different visual appearances. IC63 can be described as a "comet cloud", refers to gamma cas and is narrower and sharper defined than IC59. Spectral measurements indicate that IC59 at 590K is slightly cooler and less dense than IC63 at 630K. Both are not separate nebulae, but part of a much larger nebulous region surrounding Gamma Cas. Both nebulae have spectroscopic mid-infrared detections of molecular hydrogen and polycyclic aromatic hydrocarbons (PAHs).


Experts are discussing whether the H-a signal we capture in our images is actually an emission from the nebula, or reflection of the H-alpha light emitted by Gamma Cas, which is scattered by the dust in IC59 and IC63. This light scattering and reflection is called ERE (extended red emission). Gamma Cas is the prototype of a B0 IV star that emits significant H-alpha light. As it is slightly cooler than a BO V star, it can only slightly ionize molecular hydrogen in its environment. Thus it is possible that the H-alpha we capture in our images is a mixture of both processes: direct H-a emission from ionization and ERE.

Baerenstein Observatory

private observatory
Marcel Drechsler





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