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Click for hires
The
Coalsack is one of the most famous dark nebulae of the Southern
Hemisphere. It lies near Alpha Crucis (Acrux), the main star of the Crux
constellation, a double star with nearly equal blue components
separated by 4". At 2° to toward East (here at right) a small open
cluster is present, NGC 4609.
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| Optics | Pentax 75 apo refractor |
| Focal Length | 500 mm |
| Focal Ratio | f/6.7 |
| Exposure Time | 1 h 10 min
(single exp of 10 min) |
| CCD | Canon
EOS 5D with Baader filter |
| Sensitivity | 800 ISO |
| Location | Tivoli Farm
(Namibia) at 1350 m height |
| Date |
31 August 2011 |
| Mount | Kenko NES |
| Tracking | Lodestar with a small refractor (F.L. 100 mm, aperture 23 mm) |
| Temperature and humidity | T= +14°C, RH=27% |
| Sky brightness at zenith (with SQM-L) | 21.6 mag/arcsec^2 (Moon low on the horizon) |
| Notes | This
image is a collaborative effort of the Namibia 2011 expedition.
Processing: Lorenzo Comolli. Images by: Lorenzo Comolli, Luigi Fontana,
Giosuè Ghioldi, Emmanuele Sordini. |
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