Measurements on passages at Knowth

Victor Reijs has been able to determine the azimuth of the westerly passage of Knowth and an indicative measurement of the easterly passage azimuth has been made.
According to Brennan  ([1983], page 102) the easterly and westerly passage of Knowth would be aligned with equinox, the below will show this is not true.

Westerly passage

A plan has been made to measure the westerly passage at Site 1 of Knowth.


The minimum azimuth of the westerly passage is determined using the following methods: Evaluating these value, it is save to say that the minimum (green) azimuth of the western passage is around 259°.

Apparent altitude

The apparent altitude window that could allow light inside the passage up to the end of the passage, is between 0° (the horizon [barely no problems with trees!] and the top of Kerb stone K74 are both at this apparent altitude) and 0.4°.
This 0.4° is determined by looking at the height of the first still existing Orthostat 80. It could be that the maximum apparent altitude would have been a little bit bigger, but not more than 1.4°.

Sunniness of westerly passage

Using a stylized map of the westerly passage (taken from G. Eogan, 1986), the sunniness of the passage has been calculated (bearing in mind that I only looked at sun further away than Ort. 31). It is 2.1% or 8 days per year of sun on the Ort. 32 (and perhaps further).
This sunniness is comparable with Newgrange and Maeshowe reappearing phenomena.

Easterly passage


Because of the concrete building (within the pre-christian settlement) in front of the easterly passage, no azimuth measurements can be done in a simple way!

Kerb Stone K11 and the concrete wall
plus bridge in front of easterly passage
So using these values and the experience from the westerly passage, I assume that the azimuth of the easternlypassage will be around 85°.
This passage almost directed towards Dowth (83° 40')
The horizon view at this moment is blocked by a shed (is removed in the mean time) and trees (difficult to remove).

The rebuild entrance now looks like this:

Apparent altitude

The apparent altitude of the view could not be measured in real live. It could be that the top of kerb stone K11 is at a higher level than the ceiling of the passage (see picture 17 in Knowth, G. Eogan). In that case no sun light can penetrate the chamber.
The height of the top rim of K11 is projected on the present eastern passage:

Looking at the above picture it looks like the passage ceiling has been rebuild higher then when the excavation took place. This issue is being studied.

The horizon could have a maximum apparent altitude of around 0.4° (Donore Hill).

Changing the concrete wall

Victor Reijs has put forward a proposal to Duchas to change the walls of the modern concrete room, so that light can penetrate the easterly passage (using a state-of-art method for integrating past, present and future in own design). This change would enhance the building very much, because it integrates the neolithic, the pre-christian and the present times in a much better way. He is still awaiting their reaction.

Seeing the sun in the westerly passage


I hereby want to thank Clare Tuffy, who provided the permission to walk around Knowth to do my measurements. Ben Devine, Colm O'Brien, Anthony Murphy and Richard Moore supported me in many ways to do these measurements.

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Major content related changes: Nov. 14, 2000