RCW 75 (also known as Gum 48a) is an emission nebula (HII region) in the constellation of Centaurus. The distance to RCW 75 is estimated to be about 6,500 light years. This complex is likely associated with the very young Galactic open cluster Stock 16. This region lies at the end of an “elephant trunk” shaped molecular cloud and may be a region with triggered star formation. The primary ionizing source for the H II region is the star HD 115455, with spectral type O7.5 III. The HII region surrounds and is ionised by the young cluster Stock 16, which is part of the Cen OB1 association and contains the reflection nebula complex VdBH 60a, VdBH 60b, VdBH 60c and VdBH 60d. The region is probably physically connected to the huge and diffuse m Cen nebula. The RCW Catalogue (from Rodgers, Campbell & Whiteoak) is an astronomical catalogue of Hα-emission regions in the southern Milky Way, described in (Rodgers et al. 1960). It contains 182 objects, including many of the earlier Gum catalogue (84 items) objects. The RCW catalogue was compiled by Alexander William Rodgers, Colin T. Campbell and John Bartlett Whiteoak. They catalogued southern nebulae while working under Bart Bok at the Mount Stromlo Observatory in Australia in the 1960s.

Telescope: Planewave CDK17 (FR) f4.5
Mount: Astro Physics 1600GTO
Camera: QHY16200A/ Integral FW
Guider: AP 155EDF f5.4 / FLI PL29050
Filters: Astronomik 36mm 5nm H-alpha

H-alpha: 87×10 mins = 870 mins

Total Imaging Time: 14h 30m

Data Imaged remotely over 5 nights during April 2022.
Imaged from Observatorio El Sauce, Chile, in partnership with Fred Espenak.
Data acquisition & Processing by David Churchill.

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