Skies By Africa

Images of the Heavens By Eric Africa

SH2-155, The Cave Nebula

SH2-155, The Cave Nebula
This is a busy region in the constellation Cepheus. There are many cataloged objects in  this FOV, some of the more interesting or notable ones labeled in the annotated version (please hold cursor over the image to see the annotations). What is interesting about this wide field of view is that it contains samples of the three main types of nebulae: emission, reflection and dark.

SH2-155 is the 155th entry in a catalog of 313 "HII" regions (mostly emission nebulae made of ionized hydrogen) compiled by American astronomer Stewart Sharpless in 1959. This is a dim and diffuse emission nebula, and is nicknamed the "Cave Nebula" because of the dark nebula abutting the emission component, giving it the appearance of a cave when visually observed. Interestingly, there is another 155 in the image, vdB 155. This is the 155th entry in a catalog created by Sidney van den Bergh in 1966 of bright nebulae with embedded stars. There are many dark nebulae in this region as well. I've also labeled LDN 1215 (and hopefully not misidentified it!), a dark nebula included in the Lynds' Catalog of Dark Nebulae, published in 1962. I'm pointing it out because it reminds me of the aliens in the "Alien" movies.
Constellation: Cepheus
When Visible: August - January
Distance: Approximately 2800 light-years
Date: September 2013
Location: Rancho Hidalgo, New Mexico/td>
Exposure Details:
H-alpha: 26 x 30 Minutes binned 1x1
R: 19 x 10 Minutes binned 1x1
G: 19 x 10 Minutes binned 1x1
B: 19 x 10 Minutes binned 1x1

22.5 Hours total exposure time
Equipment Used:  Takahashi FSQ-106N on an Astro-Physics AP1200GTO mount. SBIG STL-11000 camera with 5-position filter wheel and Astrodon filters. Robofocus focuser. Externally guided with an SBIG Remote Guide Head on a Borg 50Ach refractor.
Acquisition Software:  MaximDL, TheSky6, CCDAutopilot
Processing Software: MaximDL, Photoshop CS5, IrFanView, HLVG Plugin, Carboni Actions