15
However, there is another interesting case worth discussing. The dolmen of
Viera, a megalithic tomb of the mid-third millennium BC integrating the fascinating
group of prehistoric tombs in the Antequera Archaeological Park, recently declared
as a World Heritage site by UNESCO (Ruiz González et al., 2015), was fist explored
by Michael Hoskin in his extensive archaeoastronomical research in the Iberian
Peninsula (Hoskin, 2001, and references therein). The initial datum was not very
promising (Belmonte & Hoskin, 2002: 77–80) but later observations and, among
all, detailed photographic documentation of the dolmen alignment, preparing for the
UNESCO candidacy proved otherwise. All in all, Viera was considered, and heartily
proposed, as a monument orientated to equinox sunrise. Once more the dichotomy!
Figure 2 beautifully illustrates the problem. The photograph presented there
was taken at full-moon the night of the equinox when the declination of our satellite was c. 0°, and hence mimic the exact behaviour of the sun at δ ~ 0°. The alignment seemed perfect. However, the devil is in the details and having a close
inspection at the image, a small but still perceptible effect can be ascertained, proving that the photograph was taken slightly off axis (this precision would be impossible at sunrise when strong light and shadow contrasts would preclude such clear
perception). If the correct chamber and corridor axis is considered, the moon would
have been seen a whole disk diameter to the left of the axis. Actually, the horizon
window observable from the chamber would have permitted not only the equinoctial sun light entering the chamber, but also at the day midway between the solstices, and a couple of days before the spring and after the autumn equinoxes.
Fig. 2 ‘Equinoctial’
moonrise on March 21st
2019 on the axis of the
dolmen of Viera
(Antequera, Spain): The
full-moon had a value of
the declination of virtually
0°, thus mimicking the
behaviour of the sun at the
equinox. Photograph by
courtesy of Fernando del
Pino
What Equinox?
However, there is another interesting case worth discussing. The dolmen of
Viera, a megalithic tomb of the mid-third millennium BC integrating the fascinating
group of prehistoric tombs in the Antequera Archaeological Park, recently declared
as a World Heritage site by UNESCO (Ruiz González et al., 2015), was fist explored
by Michael Hoskin in his extensive archaeoastronomical research in the Iberian
Peninsula (Hoskin, 2001, and references therein). The initial datum was not very
promising (Belmonte & Hoskin, 2002: 77–80) but later observations and, among
all, detailed photographic documentation of the dolmen alignment, preparing for the
UNESCO candidacy proved otherwise. All in all, Viera was considered, and heartily
proposed, as a monument orientated to equinox sunrise. Once more the dichotomy!
Figure 2 beautifully illustrates the problem. The photograph presented there
was taken at full-moon the night of the equinox when the declination of our satellite was c. 0°, and hence mimic the exact behaviour of the sun at δ ~ 0°. The alignment seemed perfect. However, the devil is in the details and having a close
inspection at the image, a small but still perceptible effect can be ascertained, proving that the photograph was taken slightly off axis (this precision would be impossible at sunrise when strong light and shadow contrasts would preclude such clear
perception). If the correct chamber and corridor axis is considered, the moon would
have been seen a whole disk diameter to the left of the axis. Actually, the horizon
window observable from the chamber would have permitted not only the equinoctial sun light entering the chamber, but also at the day midway between the solstices, and a couple of days before the spring and after the autumn equinoxes.
Fig. 2 ‘Equinoctial’
moonrise on March 21st
2019 on the axis of the
dolmen of Viera
(Antequera, Spain): The
full-moon had a value of
the declination of virtually
0°, thus mimicking the
behaviour of the sun at the
equinox. Photograph by
courtesy of Fernando del
Pino
What Equinox?