Penne, October 2014. The twelfth century fortified castle, which once withstood the assaults of the Crusade against the Albigensians and of the Hundred Years War, now seems to be the target of a spatial raid : arrows of different colors and light intensities, but of equal size, seem to be thrown in its direction indeed. More than arrows, these are actually starry bows or trajectories traveled by dozens of stars of various magnitudes in the sky of the Tarn during the five minutes of exposure which this shooting required. These starry bows testify the rotation of the Earth on itself. This diurnal motion whose periodicity equals 23h56min04sec leads to the successive risings of stars (including our Sun) in the eastern sky, to their culminations in the local meridian and to their disappearances beneath the western horizon. The fact that the sidereal day is substantially lower than the solar day of 24 hours moreover explains the differences between the summer and winter skies: constellations follow one another in the sky indeed, without ever remaining there - with the exception of the circumpolar constellations (Big Dipper, Little Dipper, Dragon, etc.), of course.
Information relating to this photography:
- Photographic conditions :
- [Sky] Fuji X-E2 + Fujinon Lens XF 35mm F1.4 R - F/1.4 - 300 seconds - ISO 200
- [Earth] Fuji X-E2 + Fujinon Lens XF 35mm F1.4 R - F/1.4 - 1/5 second - ISO 200
- Processing tools of the photographies : RAW file converter EX powered by Silkypix 126.96.36.199 + GIMP 2.8.10
- Optimization of displaying colors on screen : Firefox 30.0 + Module Color Management 0.5.3
Keywords : space raid, starry bows, castle of Penne, Tarn, Crusade against the Albigensians, Hundred Years War, Earth rotation, diurnal motion, succession of the constellations, summer sky, winter sky