RCW 75, also catalogued as Gum 48a, is an emission region characterized by the strong influence of the young open cluster Stock 16 (just below and right of center), which fuels and ionizes the whole nebula.
The exact distance to this nebula still has to be precisely determined. Current estimates locate it at a distance between 5200 ly and 7800 ly (1640 and 2400 parsecs, respectively) with an accepted average distance of 6500 ly. This nebulosity is interspersed with dark nebulae (especially the one giving name to the “Elephant Trunk”) and a faint reflection nebula (VdBH 60, located in the center, and fueled by the star LSS 3027, the star on the right).
This image was taken with narrowband filters and mapped to natural color. The bluish reflection nebula easily popped up from the shorter RGB images, taken to give more natural color to the stars.
Name(s): RCW 75 (Gum 48a) with Stock 16
Type: Emission Nebula with open cluster
RA: 13h 19m 31.9s
Dec: -62º 33’ 26”
Size (arcmin): 10×10 (uncertain)
Distance: 6,500 ly
Date: 2018-04-08 thru 2018-04-10
Location: iTelescope.net, SSO near Coonabarabran, NSW Australia
Size (arcmin): 36×36
Telescope: Planewave CDK 20” f/6.8
Camera: SBIG STX16803 (4096x4096pix)
Guiding: Astrodon MonsterMOAG off-axis guider
Total exposure: 21h (Ha: 12 h; OIII: 7.5 h; RGB: 1h 30m)
Processing: CCDStack, Photoshop CC 2018