| Table 2. Temporal Spans of Uncalibrated Radiocarbon Measurements. Sites are ordered by oldest radiocarbon measurement. Sources are available in Table 3, a complete list of the radiocarbon measurements used (a separate rich text format file). | |||
| Monument | Valley/orient | Oldest Measurement | Most Recent |
| Huaca de los Idolos | Supe | 4900 ± 160 | 3970 ± 145 |
| Moxeke | Casma | 4655 ± 95 | 3070 ± 85 |
| Tortugas | Casma | 4540 ± 200 | 3750 ± 65 |
| Bandurria | Huaura | 4530 ± 80 | 4300 ± 90 |
| Huaca Prieta | Chicama | 4380 ± 270 | 2631 ± 300 |
| Huaca de los Sacrificios | Supe | 4260 ± 150 | 3950 ± 150 |
| Las Haldas | Casma | 3960 ± 80 | 2360 ± 90 |
| Cerro Sechín | Casma | 3820 ± 50 | 2100 ± 160 |
| Chupacigarro (Caral) | Supe | 3815 ± 90 | |
| Chupacigarro Chico | Supe | 3815 ± 140 | |
| La Florida | Rimac | 3810 ± 170 | 3645 ± 120 |
| El Paraíso | Chillón | 3790 ± 100 | 3020 ± 60 |
| Cerro Obrero | Santa | 3690 ± 60 | |
| Huaca de los Reyes | Moche | 3680 ± 80 | 2800 ± 60 |
| Salinas de Chao | Chao | 3600 ± 90 | |
| Mina Perdida | Lurín | 3520 ± 100 | 2870 ± 90 |
| Huaca Herederos Chica | Moche | 3450 ± 70 | 3040 ± 80 |
| Sechín Alto | Casma | 3400 ± 100 | |
| Garagay | Rimac | 3340 ± 70 | 2730 ± 70 |
| Huaca Lucia | La Leche | 3273 ± 163 | |
| Cardal | Lurín | 3120 ± 90 | 2690 ± 90 |
| Purulén | Zaña | 3120 ± 80 |
The heliacal rising of the star is when it is visible just before sunrise for the first time, after sharing the sky with the sun for some time. Typically this would be some ten degrees ahead of the sun, so that the dawn light does not hide it. It depends, of course, on how bright the star or object is. Dawn is considered to start when the sun is twelve degrees below the horizon, and night to start when the sun has dropped six degrees, the difference being due to the greater sensitivity of the eye to the faint light of dawn.
As the sun travels 360 degrees in 24 hours, (or rather the earth rotates) this is 15 degrees per hour, so a star might be visible 40 minutes before sunrise or even 24 minutes.
At the end of June, the sun rises shortly after 6 am. So we should be looking to the North East from 5.20 am to see the heliacal rising of the Pleiades. A planetarium simulation gives us 8th of June, as the day when the Pleiades rises over the ideal horizon at 5.20 am, and 10 or 11th June, when the Pleiades rises at 5.00 am.
If it were visible within six degrees of the sun, we would be able to see it five days earlier, on 3rd June.
In both cases, I am imagining a flat horizon. If the Pleiades is rising above mountains, then it may not be visible until it is are several degrees above the horizon. This will affect the day when they first become visible, because the sun will still have to be six degrees or more below the horizon, and the separation of Pleiades and sun will need to be that much greater. The angular separation between the Pleiades and the sun increases by about one degrees per day, so a ten degree horizon would delay the heliacal rising by ten days.
To put it another way, the Pleiades rises four minutes earlier every day, so a ten degree horizon would be forty minutes later. Clearly, the rising of the Pleiades could be from 3rd of June in optimum conditions to 16th of June in hilly country with poor viewing.
To see a good rising Pleiades, like a great sunrise, you want to stand on a cliff by the sea, or on a mountaintop.
Looking from the southern end of the rock of the Llama Trains, we will see the Pleiades rise above the shoulder of the mountain slopes descending into the valley. The elevation of the mountain side from here is about eighteen degrees. The Pleiades would cross the invisible horizon, on a bearing of 065 , or 65 degrees east of north, and with good visibility it might be seen in the first week of June. But it will not be visible above the mountain slope until a week or two later, when it will have shifted several degrees to the north – 60 degrees east of north, rather than the 65 degrees east of north that it appears on the horizon.
The platform on the stony hillside above the orchard is some thirty metres higher. From here, the elevation to the shoulder of the mountain is just fourteen degrees. The Pleiades will be visible four days earlier from this vantage point, at 61 or 62 degrees east of north. It will rise, according to simulations on Google Earth, from the cleft on the horizon formed by the mountain side of the valley, and the lower rising hillside in the background where
lie the ruins of the town of Huancani.
The same simulation tells us that it is still visible above the absolute, invisible horizon at 7 pm, shortly after sunset, on 28th of April, after which it disappears into the sun’s light. Behind the elevated horizon of the mountains, this again might occur a week or two earlier.
This allows the orientation of U temples a wide latitude, if they are pointing towards the Pleiades or another star formation rising above the mountains. But the Pleiades rising no longer offers a useful record of the seasons, as it now varies by many weeks and even two months from the mountain to the valley.
The effects of precession using Kstar are to increase the bearing to 69 degrees 1000 years earlier, and to 73 degrees 2000 years ago.
The flat top mounds around the present day Parque de los Leyendas in Lima are thought to have been created at different periods. The most westerly, just outside the Park are believed to be from the Lima people, whilst the smaller mounds within are from the Ychsma period, 1000 AD up to the coming of the Incas. These mounds are so close together that they are observing the same horizon. But the orientations differ from 028 degrees East of north, for the Huaca San Marcos and to 018 degrees for Huaca Tres Palos, which dominates the walk towards to park entrance from the main road. If the change was due to adjusting the new structures to point towards the same sky feature, which had shifted due to precession, the time difference would be 2000 years. But the earlier Maranga buildings are thought to be from 200 AD, less than a thousand years before the Ychsma mounds. The line of sight could be towards the horizon point of Alpha Cetai or Eta Cetai.
The Earth’s axis rotates slowly westward about the poles of the ecliptic, completing one circuit in about 26,000 years. This movement, known as precession, causes the coordinates of stationary celestial objects to change continuously, if rather slowly. Therefore, equatorial coordinates (including right ascension) are inherently relative to the year of their observation, and astronomers specify them with reference to a particular year, known as an epoch. Coordinates from different epochs must be mathematically rotated to match each other, or to match a standard epoch.[7] Right ascension for “fixed stars” near the ecliptic and equator increases by about 3.05 seconds per year on average, or 5.1 minutes per century, but for fixed stars further from the ecliptic the rate of change can be anything from negative infinity to positive infinity.