Crux and Coalsack
Crux is a Southern Hemisphere constellation otherwise known as the Southern Cross. It is one of the most easily recognizable constellations, because its four main stars all have an apparent visual magnitudes greater than +2.8.Crux is one of the 88 modern constellations defined by the International Astronomical Union (Wikipedia).
Crux also contains the bright and colourful open cluster known as the Jewel Box (NGC 4755) and the extensive dark nebula, known as the Coalsack Nebula, in its southeastern corner. The Coalsack is the most prominent dark nebula in the sky and is easily visible to the naked eye as a dark patch or hole in the southern Milky Way. It measures about five by seven degrees, and is 600 light-years away. A portion of the nebula extends beyond Crux into the constellations of Musca and Centaurus.
Crux (abbrev. = Cru; genitive = Crucis) covers 68 square degrees or 0.21% of the celestial sphere making it the smallest of the 88 constellations. It contains 49 stars brighter than apparent magnitude 6.5, the brightest star being Acrux. See the Crux Star Chart for a figure illustrating this constellation including the identification of its brighter stars.
For more information see the entries for Crux at Wikipedia and U. Wisconsin. For a chart of Crux, see Cru (IAU).
Technical Details
- Object: Crux and Coalsack
- Date/Time: 2018 Apr 13 at 01:57 UTC
- Location: Atacama Lodge, San Pedro de Atacama, Chile
- Mount: iOptron iEQ30 Pro GEM
- Lens: Nikkor 200mm f/4
- Camera: Nikon D750
- Field of View: 10.3° x 6.9° at 8.2 arc-sec/pixel
- Exposure: 4 x 180s, f/4, ISO 3200 and 30s, f/4, ISO 3200 with Cokin A830 Diffusion Filter
- File Name: Crux18-02w.jpg
- Pre-Preprocessing (Starry Sky Stacker): Sub Exposures were Flat-Fielded, Registered and Stacked
- Processing (Adobe Lightroom): White Balance, Curves, Noise Reduction
- Processing (Photoshop CC): Layers, Opacity (Cokin A830 Diffusion Filter image)
- Original Image Size: 4016 × 6016 pixels (17.9 MP); 13.4" x 20.1" @ 300 dpi
- Rights: Copyright 2018 by Fred Espenak. All Rights Reserved. See: Image Licensing.