Sh2-185 — Ghost of Cassiopeia

About

A large cloud of ionised hydrogen centred on Gamma Cassiopeiae, a bright star, and about 2° across by one source. Two cometary nebulae lie inside it, IC 63 and IC 59, and the brighter IC 63 is known as the Ghost Nebula.

Imaging tips

• The star outshines the clouds by roughly 9 magnitudes, so glare control matters.
• The field holds both a red emission glow and blue reflection light: one imager took 18 ten-minute frames each of L, R, G and B, about 12 hours.
• IC 63 sits closer to the star and shows stronger Hα emission, while IC 59 leans more toward reflection, so add Hα to broadband if you want both.
• One imager framed 1.8° by 1.21°. By one source the cloud spans about 2°, close to the width of a 156′ frame, so a wide lens or mosaic suits it.
• Best in September and October; it peaks near 79° altitude from 50°N.