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3.2.4 Viewshed from the WNW Entrance of the Observatory Building
to the Fortified Temple
The Observatory Building (OB) had an entrance facing WNW, symmetrical with
the WOP facing ESE. The adjacent later building, Structure 5 (here referred to as
‘OB2’) is also likely to have had an entrance facing WNW, although that part of the
structure has been destroyed. Symmetry principles operating elsewhere on the site
suggest the possibility that astronomical observations were also made from the OB
entrance or both entrances. The WNW entrances to the two buildings faced the
Fortified Temple, which stands out prominently on the horizon. The NNE wall of
the OB (301.7° azimuth) is aligned upon the centre of the circular Southern Keep
(301.8° azimuth) as seen from the WNW entrance. Similarly, that of OB2 (300.8°
azimuth) is aligned upon the centre of the circular Southern Keep as seen from its
entrance (301.0° azimuth). However, the declination (+29.0° from OB1NW, +27.7°
from OB2NW) is well outside the solar range.
In fact, a second century BC viewer standing at the OB entrance in the late afternoon at the June solstice would have seen the sun above the southern wall of the
Temple of the Pillars moving slightly to the left while descending, eventually setting
into the gap immediately to the left of the Temple. The right-hand side of the solar
disc, at declination +24.0°, would just have touched the base of the outer side of the
Temple’s southern wall. At all other times of year, the sun would have set further to
the south: in other words, it would never (quite) have been seen to set behind the
Temple itself.
The declination of the Southern Keep does, however, correspond closely to the
theoretical northernmost setting point of the moon (δ = +28.9° around 200 BC, falling slightly to +28.6° by the early second millennium AD). While the rising or setting position of the moon (unlike that of the sun) changes a great deal from day to
day (further complicated by the moon’s changing phases), the significance of this is
that the full moon close to the December solstice, towards which the Chankillo site
is broadly oriented, would have set as far north as this in favorable years within the
18.6-year lunar node cycle (a time known technically as the ‘major lunar standstill’).
Added to this, the declination of the foot of the outer side of the outer enclosing
wall as seen from the entrance to the OB, +18.6°, corresponds almost exactly to the
northern minor standstill limit (+18.6° around 200 BC, falling slightly to +18.3° by
the early second millennium AD). This limit (being the minimum of the monthly
maximum limits of the moon’s motions over the course of an 18.6-year lunar node
cycle) is extremely unlikely to have had cultural meaning in itself outside a modern
Western cultural context (Gonzales-Garcia, 2014), but the fact that the highest part
of the Temple profile spans the range between the northern major and minor standstill limits could be significant. This represents the range of positions (over an 18.6year node cycle) where the full moon would have been seen to set at dawn around
the time of the December solstice, the very time when the sun would be seen to rise
out of the top of Tower 13 as viewed from the opposite entrance (WOP). Most often,
the full moon would have been seen to set close to the Southern Keep (at around the
The Chankillo Solar Observatory and Ceremonial Centre: A Heritage for the World
3.2.4 Viewshed from the WNW Entrance of the Observatory Building
to the Fortified Temple
The Observatory Building (OB) had an entrance facing WNW, symmetrical with
the WOP facing ESE. The adjacent later building, Structure 5 (here referred to as
‘OB2’) is also likely to have had an entrance facing WNW, although that part of the
structure has been destroyed. Symmetry principles operating elsewhere on the site
suggest the possibility that astronomical observations were also made from the OB
entrance or both entrances. The WNW entrances to the two buildings faced the
Fortified Temple, which stands out prominently on the horizon. The NNE wall of
the OB (301.7° azimuth) is aligned upon the centre of the circular Southern Keep
(301.8° azimuth) as seen from the WNW entrance. Similarly, that of OB2 (300.8°
azimuth) is aligned upon the centre of the circular Southern Keep as seen from its
entrance (301.0° azimuth). However, the declination (+29.0° from OB1NW, +27.7°
from OB2NW) is well outside the solar range.
In fact, a second century BC viewer standing at the OB entrance in the late afternoon at the June solstice would have seen the sun above the southern wall of the
Temple of the Pillars moving slightly to the left while descending, eventually setting
into the gap immediately to the left of the Temple. The right-hand side of the solar
disc, at declination +24.0°, would just have touched the base of the outer side of the
Temple’s southern wall. At all other times of year, the sun would have set further to
the south: in other words, it would never (quite) have been seen to set behind the
Temple itself.
The declination of the Southern Keep does, however, correspond closely to the
theoretical northernmost setting point of the moon (δ = +28.9° around 200 BC, falling slightly to +28.6° by the early second millennium AD). While the rising or setting position of the moon (unlike that of the sun) changes a great deal from day to
day (further complicated by the moon’s changing phases), the significance of this is
that the full moon close to the December solstice, towards which the Chankillo site
is broadly oriented, would have set as far north as this in favorable years within the
18.6-year lunar node cycle (a time known technically as the ‘major lunar standstill’).
Added to this, the declination of the foot of the outer side of the outer enclosing
wall as seen from the entrance to the OB, +18.6°, corresponds almost exactly to the
northern minor standstill limit (+18.6° around 200 BC, falling slightly to +18.3° by
the early second millennium AD). This limit (being the minimum of the monthly
maximum limits of the moon’s motions over the course of an 18.6-year lunar node
cycle) is extremely unlikely to have had cultural meaning in itself outside a modern
Western cultural context (Gonzales-Garcia, 2014), but the fact that the highest part
of the Temple profile spans the range between the northern major and minor standstill limits could be significant. This represents the range of positions (over an 18.6year node cycle) where the full moon would have been seen to set at dawn around
the time of the December solstice, the very time when the sun would be seen to rise
out of the top of Tower 13 as viewed from the opposite entrance (WOP). Most often,
the full moon would have been seen to set close to the Southern Keep (at around the
The Chankillo Solar Observatory and Ceremonial Centre: A Heritage for the World