Sh2-28 (RCW 145) in Sagittarius

© Velimir Popov & Emil Ivanov 2020
Size: 1800 px

Sh2-28 is a large but faint HII region next to the Trifid nebula.It is ionised by the O9Ib supergiant LS 4551 and the O-class LS 4538. It lies in the direction of the supernova remnant SNR G006.4-00.1 (W 28). Unfortunately SIMBAD (and therefore all plotting softwares) uses the incorrect original Sharpless coordinates for Sh 2-28 rather than the corrected BFS coordinates. This is a reason the nebula is off-centre on this image. Sh2-28 and RCW 145 are the same object. Perhaps because of the errors in the original Sharpless coordinates for Sh 2-28, the RCW catalog identifies RCW 145 as Sh 2-26. Sh 2-26 is a smaller even fainter nebula further from the galactic plane. The W 28 supernova remnant appears to be further away at a distance of 1800 to 3300 pc [Giuliani, A., Tavani, M., Bulgarelli, A., et al. (2010)] but, on the other hand, a 1978 paper by Crampton and Georgelin [Crampton, D., Georgelin, Y. M., & Georgelin, Y. P. (1978)] concludes that the nebula is the optical equivalent of W 28 and includes the supernova remnant. It appears to be associated with M 20, the Trifid nebula. Crampton and Georgelins conclude that Sh 2-28 is ionised by LSS 4551 and LSS 4538.


Image details:


Center of field RA 18:02:18 (h:m:s)
Center of field DE -23:30:56 (deg:m:s)
Size 1.59 x 1.17 (deg)
Pixel scale: 3.19 (arcsec/pixel)
Orientation: Up is 245 degrees E of N
Charts and image details obtained from
Optic(s): 12" ASA Astrograph at F/3.6
Mount: ASA DDM85 Standard
Camera: SBIG STL 11000 M
Filters: Luminance, Red, Green, Blue, Astronomik filters; Ha Baader filter
Dates/Times: 2.Sep. 2018, 11.Jul.2020
Location: IRIDA Observatory, BG, longitude: E 24 44' 18", latitude: N 41 41' 42"
Exp. Details: ;L:6x10min, R:6x10 min, G:6x10 min, B:6x10 min;Ha:6x15 min;; Bin 2 Total exp.time: 330 min. (5:30 hrs)
More details: Dark and flat frames reduction
Processing: PixInsight / PS
Copyright: Velimir Popov and Emil Ivanov 2020. All Rights Reserved
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