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0.45 m above the floor in the case of the long gallery in the atrium, or 0.65 m in the
case of the Room 3 gallery, then even at altitude 3.6° the sun would already have
been high enough for sunlight to reach to the bottom of the back wall. Otherwise,
the bottom of the wall would have remained in darkness at this point. As the sun
rose in the sky and moved slightly to the left, the top of the lit stripes would gradually
have descended the wall. At the same time, they would have narrowed somewhat
(while their centres remained equally far apart) and moved slightly to the left. They
would also have extended further down onto the floor.
At other times in the year, the height of the bright stripes at first glance would
have varied slightly because of the variation in the altitude of the eastern skyline,
distant 50 km, from a minimum of 3.2° at the equinoxes to a maximum of 6.6° at the
June solstice. A more noticeable difference would have occurred because sunlight
now entered the galleries from a direction no longer perpendicular to the back walls
and lines of pillars. The width of the bright stripes would have been noticeably narrower. Whether by accident or design, the width of the bright stripes shrinks to zero
more or less exactly at the time of the June solstice. In other words, the width of the
bright stripes offered another calendrical indicator, simple and direct, that operated
throughout the year.
Furthermore, at the equinoxes the displacement of the stripes was almost exactly
equal to the distance from one pillar (or space) to the next, meaning that a viewer
looking directly into the back gallery from the atrium or Room 3 patio would have
seen the bright stripes on the back wall aligning in the gaps between the pillars. This
only happened around the December solstice (no displacement), the equinoxes (displacement by one pillar) and the approach to the June solstice (displacement by two
pillars), by which time the stripes would have been very narrow. At other times, the
bright stripes would have been partially or completely hidden behind the pillars.
3.3.2 Effect of the Slits
Around the December solstice, each 1 m-wide dark stripe would have additionally
contained three bright rectangles produced by sunlight passing through the three
slits in the pillar concerned. These would have been most pronounced at the moment
of sunrise on days very close to the solstice, when the sun would have shone more
or less directly through the slits, producing full-size (0.20 × 0.08 m) rectangles of
light on the walls behind. As the sun rose in the sky the slits would have decreased
in height (and slightly in width) as well as descending the walls. A few days after
the solstice, the images of the slits would have become noticeably narrower, as sunlight began to enter the galleries at a significantly oblique angle. For the central
0.77 m long slit, once this horizontal angle had exceeded 5.9°, sunlight was no
longer able to penetrate the length of the slit. For the side slits, where the incision
may have decreased the effective length to, say, 70 cm, the angle was about 6.5°.
This occurs when the sun’s azimuth falls below about 110°, which happens around
30 days either side of the December solstice. In other words, the pattern of ‘bright
The Chankillo Solar Observatory and Ceremonial Centre: A Heritage for the World
0.45 m above the floor in the case of the long gallery in the atrium, or 0.65 m in the
case of the Room 3 gallery, then even at altitude 3.6° the sun would already have
been high enough for sunlight to reach to the bottom of the back wall. Otherwise,
the bottom of the wall would have remained in darkness at this point. As the sun
rose in the sky and moved slightly to the left, the top of the lit stripes would gradually
have descended the wall. At the same time, they would have narrowed somewhat
(while their centres remained equally far apart) and moved slightly to the left. They
would also have extended further down onto the floor.
At other times in the year, the height of the bright stripes at first glance would
have varied slightly because of the variation in the altitude of the eastern skyline,
distant 50 km, from a minimum of 3.2° at the equinoxes to a maximum of 6.6° at the
June solstice. A more noticeable difference would have occurred because sunlight
now entered the galleries from a direction no longer perpendicular to the back walls
and lines of pillars. The width of the bright stripes would have been noticeably narrower. Whether by accident or design, the width of the bright stripes shrinks to zero
more or less exactly at the time of the June solstice. In other words, the width of the
bright stripes offered another calendrical indicator, simple and direct, that operated
throughout the year.
Furthermore, at the equinoxes the displacement of the stripes was almost exactly
equal to the distance from one pillar (or space) to the next, meaning that a viewer
looking directly into the back gallery from the atrium or Room 3 patio would have
seen the bright stripes on the back wall aligning in the gaps between the pillars. This
only happened around the December solstice (no displacement), the equinoxes (displacement by one pillar) and the approach to the June solstice (displacement by two
pillars), by which time the stripes would have been very narrow. At other times, the
bright stripes would have been partially or completely hidden behind the pillars.
3.3.2 Effect of the Slits
Around the December solstice, each 1 m-wide dark stripe would have additionally
contained three bright rectangles produced by sunlight passing through the three
slits in the pillar concerned. These would have been most pronounced at the moment
of sunrise on days very close to the solstice, when the sun would have shone more
or less directly through the slits, producing full-size (0.20 × 0.08 m) rectangles of
light on the walls behind. As the sun rose in the sky the slits would have decreased
in height (and slightly in width) as well as descending the walls. A few days after
the solstice, the images of the slits would have become noticeably narrower, as sunlight began to enter the galleries at a significantly oblique angle. For the central
0.77 m long slit, once this horizontal angle had exceeded 5.9°, sunlight was no
longer able to penetrate the length of the slit. For the side slits, where the incision
may have decreased the effective length to, say, 70 cm, the angle was about 6.5°.
This occurs when the sun’s azimuth falls below about 110°, which happens around
30 days either side of the December solstice. In other words, the pattern of ‘bright
The Chankillo Solar Observatory and Ceremonial Centre: A Heritage for the World