IC 63 is a reflection and emission nebula located ~550 light-years away in the constellation Cassiopeia. It is shaped by the intense ultraviolet radiation of Gamma Cassiopeiae (γ Cas), a B-type star with a surface temperature of ~25,000 K and a variable magnitude of 2.2 to 2.5. The ionizing radiation from γ Cas excites hydrogen in IC 63, producing a significant red Hα emission („Cassiopeia`s Ghost“), while interstellar dust reflects its blue light (not captured due to the used Hα-filter – B-Filter captures will follow!).

Strange Spikes …

First of all, many thanks to Matthias Pfragner (from our StAV, the Styrian Astronomers‘ Association) for quickly answering my question about why my spikes suddenly looked so interrupted (by the way, Spikes are the striking line diffraction figures around the brighter stars that come from the secondary mirror mounts of the Newtonian telescopes).

In general, about the diffraction pattern caused by the secondary mirror struts: A larger aperture (or a faster optical system) results in more prominent, sharper, and brighter diffraction spikes. Longer wavelengths, such as H-alpha, produce less pronounced spikes compared to shorter wavelengths like blue light. In monochromatic imaging (using narrowband filters) an additional effect occurs: gaps appear within the spikes because the other wavelengths, which would normally fill these gaps in unfiltered or broadband images, are absent. Broadband images show the rainbow-like color gradient along the spikes. Striped spikes with interruptions therefore appear in captures with narrowband filters only.

An L-RGB session will follow …

…especially to catch the blue reflection nebula and correct the striped false color stars 🙂