MAP OF KNOWN AND/OR SUSPECTED ASTRONOMICAL ALIGNMENTS IN THE BOYNE VALLEY UNESCO WORLD HERITAGE SITE
BY MICHAEL O'CALLAGHAN
I designed this provisional map in 2001 to identify all the astronomical alignments of megalithic sites in the Brú na Bóinne area, and scientifically validate their known and/or suspected astronomical orientations. I invited people to improve the map through field observations in situ during the Spring and Autumn Equinoxes, Summer and Winter Solstices, February and November cross-quarter days, the major and minor lunar standstills, and other relevant dates.
Readers unfamiliar with astroarchaeology should bear in mind that because the astronomical alignments from any particular monument are always relative to the contours of the locally visible horizon (rather than a theoretical flat one), azimuths from different sites to an identical astronomical event – such as Equinox sunrise – are not necessarily parallel. The accurate measurement of azimuths also requires the use of a (gyro)-theodolite or GPS, because local magnetic anomalies associated with some of the monuments make compass bearings inaccurate (e.g. azimuth measurements taken by compass inside the passages at Knowth have been found to be off by 14 degrees.)
Note that the procedure described above does not include the dating of the monuments themselves or the investigation of related astronomical references in the relevant mythological texts and local folklore, which should be undertaken separately.
To create a more accurate map, it would have been necessary to invest in a digital 25-inch to the mile Ordnance Survey map of the whole Brú na Bóinne area based on aerial photography, for more accurate determination of the position of the monuments, the azimuths of their alignments, and their known and/or suspected astronomical orientation. This would have served as the basis for a scientific research programme, involving field trips, statistical analysis and astronomical simulations. It would also have been useful to develop a 3-D GIS model of the entire area to facilitate the systematic storage and retrieval of all data obtained during this process.
The topography of the map shown above is derived from a scanned Ordnance Survey of Ireland 1:50,000 map based on aerial photography. All roads, non-megalithic buildings, electrical power lines and wooded areas have been omitted for the sake of clarity. In 2001 there were at least 52 known megalithic sites in the Boyne Valley area, of which only the principal ones are shown here. Local field research by Anthony Murphy and others suggests that 30% of the area's existing monuments remain officially undiscovered and undocumented, including a small mound and earthworks complex in the field immediately West of Knowth, and a very conspicuous mound near the Boyne East of Dowth. More monuments have since been discovered in the area.
The alignments on the map are numbered in a clockwise sequence starting with No. 1 for Newgrange North, and identified by black letters. The monuments may be distinguished by their corresponding symbols and are identified by white letters. The outlying great circle standing stones at Newgrange are identified according to the GC# system used by Michael J. O'Kelly. Note that the great chambered cairn at Knowth is surrounded by 17 smaller satellite cairns not shown on this map; sites I, J, K, L, T and Z are also passage mounds, sites A, B, E and S are tumuli, and sites F, G, H and U are ruined.
The notes below provide additional data as follows: red text describes the known and/or suspected astronomical alignments, black text to known sources and comments (see end of page for source references), and a provisional rating of the probability of an astronomical alignment indicated by the number of stars from 1 (suspected), 2 (possible), 3 (probable), 4 (almost certain), to 5 (confirmed).
Many thanks to Anthony Murphy for the confirmation of alignments made by him, and also to Richard Moore and Raymond Balfe.
Readers unfamiliar with astroarchaeology should bear in mind that because the astronomical alignments from any particular monument are always relative to the contours of the locally visible horizon (rather than a theoretical flat one), azimuths from different sites to an identical astronomical event – such as Equinox sunrise – are not necessarily parallel. The accurate measurement of azimuths also requires the use of a (gyro)-theodolite or GPS, because local magnetic anomalies associated with some of the monuments make compass bearings inaccurate (e.g. azimuth measurements taken by compass inside the passages at Knowth have been found to be off by 14 degrees.)
Note that the procedure described above does not include the dating of the monuments themselves or the investigation of related astronomical references in the relevant mythological texts and local folklore, which should be undertaken separately.
To create a more accurate map, it would have been necessary to invest in a digital 25-inch to the mile Ordnance Survey map of the whole Brú na Bóinne area based on aerial photography, for more accurate determination of the position of the monuments, the azimuths of their alignments, and their known and/or suspected astronomical orientation. This would have served as the basis for a scientific research programme, involving field trips, statistical analysis and astronomical simulations. It would also have been useful to develop a 3-D GIS model of the entire area to facilitate the systematic storage and retrieval of all data obtained during this process.
The topography of the map shown above is derived from a scanned Ordnance Survey of Ireland 1:50,000 map based on aerial photography. All roads, non-megalithic buildings, electrical power lines and wooded areas have been omitted for the sake of clarity. In 2001 there were at least 52 known megalithic sites in the Boyne Valley area, of which only the principal ones are shown here. Local field research by Anthony Murphy and others suggests that 30% of the area's existing monuments remain officially undiscovered and undocumented, including a small mound and earthworks complex in the field immediately West of Knowth, and a very conspicuous mound near the Boyne East of Dowth. More monuments have since been discovered in the area.
The alignments on the map are numbered in a clockwise sequence starting with No. 1 for Newgrange North, and identified by black letters. The monuments may be distinguished by their corresponding symbols and are identified by white letters. The outlying great circle standing stones at Newgrange are identified according to the GC# system used by Michael J. O'Kelly. Note that the great chambered cairn at Knowth is surrounded by 17 smaller satellite cairns not shown on this map; sites I, J, K, L, T and Z are also passage mounds, sites A, B, E and S are tumuli, and sites F, G, H and U are ruined.
The notes below provide additional data as follows: red text describes the known and/or suspected astronomical alignments, black text to known sources and comments (see end of page for source references), and a provisional rating of the probability of an astronomical alignment indicated by the number of stars from 1 (suspected), 2 (possible), 3 (probable), 4 (almost certain), to 5 (confirmed).
Many thanks to Anthony Murphy for the confirmation of alignments made by him, and also to Richard Moore and Raymond Balfe.
ALIGNMENT DETAILS Description, sources, and comments.
1. From Newgrange due North over henge V. (Martin Brennan and Danny Sullivan. Extends in reverse direction South over henge P as line 22.)Rating: * * * * * 2. From main cairn at Knowth over Cairn T to sunrise at Summer Solstice. (Assumed by me because this line and its neighbouring line 3 have a similar orientation to line 7, which is said to be thus oriented by Danny Sullivan. Independently identified by Richard Moore and Anthony Murphy during observations in early 1999. Anthony Murphy thinks that cairn T can be seen from Knowth, but was unable to check the actual alignment because of Knowth being closed to the public at 5am. Alignment and astronomical orientation need to be checked in situ.)Rating: * *
3. From unnumbered tumulus at SW corner of the map past edge of main cairn at Knowth either close to or over Cairn T, to sunrise at Summer Solstice. (Suspected by me because this line and its neighbouring line 2 have a similar orientation to line 7, which is said to be thus oriented by Danny Sullivan. Converges with lines 2 and 4 close to a souterrain indicated by a small white dot on the map. Alignment and astronomical orientation need to be checked in situ.)Rating: * *
4. From cairn I due North over point X. (Assumed by me because point X is the apparent intersection of lines 5, 10, and 16; it would be worth having a look around for any evidence of a ruined megalithic site at this location. If my location of point X is inaccurate, the alignment could also be from cairn J (rather than cairn I) due North via point X, beyond which this line converges with line 3 close to a souterrain indicated by a white dot on the map. Alignment and astronomical orientation need to be checked in situ.)Rating: * * * *
5. From tumulus A over or very close to cairn U through point X to the cairn (identified as a "barrow" on the OS map) at North East corner of this image. (Spotted by me, although the contours of the hill of Dowth would appear to prevent intervisibility between all four points on this line. Unsure of astronomical alignment, if any. Extends in reverse direction as line 23. Alignment and possible astronomical orientation need to be checked in situ.)Rating: *
6. From the unidentified cairn near the bend in the Boyne close to the North East corner of the map, due South to the summit of Redmountain. (Assumed by me since the alignment seems accurate and Redmountain – whose summit also lies at the intersection of lines 17 and 18 – is the most prominent hill overlooking whole the Brú na Bóinne area.)Rating: * * *
7. From central chamber of Newgrange via its outlying great circle standing stone GC10 to the Summer Solstice sunrise. (Danny Sullivan. Alignment and astronomical orientation need to be checked in situ.)Rating: * * *
8. From tumulus E over Dowth to sunrise at Summer Solstice. (Assumed by me because this line seems parallel to line 7 on the map. Independently identified by AnneMarie Moroney, Richard Moore and Anthony Murphy, and observed in Summer 2000. Could this be an extension of the line mentionned by Martin Brennan – not shown on this map – which runs in the reverse direction from Dowth to Winter Solstice sunset? ). Rating: * * * * *
9. From Newgrange via its outlying great circle standing stone GC8, over Dowth to minor lunar standstill moonrise North. (Reported by Martin Brennan and Danny Sullivan. The reverse alignment, from Dowth over Newgrange to the minor lunar standstill South was onfirmed during observations by Anthony Murphy, Richard Moore and Raymond Balfe at Dowth on 14 November 2000, when the sunset occurs at the same azimuth as the minor lunar standstill.) Rating: * * * * *
10. From mound W due East through point X to sunrise at Spring and Autumn Equinoxes. (Assumed by me. Alignment and astronomical orientation need to be checked in situ.) Rating: *
11. From Newgrange over cairn I and henge or mound Q. (Noticed by me, unsure of astronomical alignment, if any. Extends in reverse direction as line 27. Anthony Murphy reports that the gaps in mound Q are aligned to the Summer Solstice sunrise. Alignment and astronomical orientation need to be checked in situ. ) Rating: *
12. From henge R over cairn H. (Noticed by me, unsure of astronomical alignment, if any. Extends in reverse direction as line 28. Alignment and astronomical orientation need to be checked in situ.) Rating: * *
13. From Eastern passage of Knowth, apparently over or close to the summit of the unnamed 104m. hilltop on the Eastern edge of the map, to sunrise around Spring and Autumn Equinoxes. (Assumed by Martin Brennan. The penetration of the sunbeam into the Eastern passage can no longer be checked in situ because of the concrete slab – erected by Dúchas and the Royal Irish Academy – which now to block the entrance, but it should be verifiable by matching the Equinox sunrise azimuth with that of the passage [determined by Tom Ray and Frank Prendergast in 1997 as 85 degrees, i.e. 5 degrees North of due East, based on a flat horizon]. This line appears to intersect with line 14 on the hilltop. Alignment and astronomical orientation need to be checked in situ.) Rating: * * *
14. From henge V over henge (or cairn?) S to summit of unnamed 104m. hilltop. (Noticed by me. The OS map refers to site S as an earthwork, whilst M.J. O'Kelly refers to it as a tumulus. Similar orientation to lines 17, 33 and 35, but unsure of astronomical orientation, if any. Appears to intersect on hilltop with line 13 from the Eastern passage of Knowth. Extends in reverse direction as line 40. Alignment and astronomical orientation need to be checked in situ.) Rating: *
15. From Newgrange due East over cairn U to sunrise at Spring and Autumn Equinoxes. (Martin Brennan. This line appears to intersect with the summit of the nearby 95m hilltop above the village of Donore – i.e. Dún Uabhair – [just off the Eastern edge of the map]; curiously, this name means the Fort of Pride or Fort of Merriment in Irish; might this have been a locus for ritual celebration on the Equinoxes? Extends West from Newgrange as line 30. Alignment and astronomical orientation need to be checked in situ.) Rating: * * * *
16. From point X above the river Mattock over edge of mound (or henge) Q to unnamed earthwork at South East corner of the map. (Noticed by me, although the latter henge appears not to be intervisible from henge Q due to the shoulder of Redmountain getting in the way. Unsure of astronomical alignment, if any. Alignment and astronomical orientation need to be checked in situ.) Rating: *
17. From tumulus M over tumulus E to summit of Redmountain. (Noticed by me because it intersects at the summit of this hill with lines 18 and 19, and has an orientation similar to lines 14 and 33. Unsure of astronomical alignment, if any. Extends in reverse direction as line 35 which might be oriented to the minor lunar standstill. Alignment and astronomical orientation need to be checked in situ.) Rating: * *
18. From summit of Redmountain, the highest point in the Brú na Bónne area, apparently over cairn H and henge (or cairn?) W, possibly to the major lunar standstill. (Noticed by me. Possibly aligned to the major lunar standstill because its orientation is similar to line 21, which runs from cairn A over Newgrange and which is thus oriented according to Brennan. Intersects at hilltop with lines 17 and 19. Extends in reverse direction as line 39. Alignment and astronomical orientation need to be checked in situ.) Rating: * *
19. From summit of Redmountain, apparently due North to unnamed cairn near North East corner of the map. (Noticed by me. Intersects with lines 17 and 18. Alignment and astronomical orientation need to be checked in situ.)Rating: * * * *
20. From cairn I, apparently due North to point X above the river Mattock. (Noticed by me. Intersects with lines 5 and 16 at point X, and converges along with lines 2 and 3 close to a souterrain shown by a small white dot East of where these lines meet on the map. Extends in reverse direction as line 3. Alignment and astronomical orientation need to be checked in situ.)Rating: * *
21. From backstone of passage of main cairn at Newgrange over its great circle standing stone GC1 in front of the entrance, and thence over tumulus A to sunrise at Winter Solstice. (Michael J. O'Kelly, Martin Brennan et. al. Extends in reverse direction as line 36 to major lunar standstill. The solsticial alignment is confirmed beyond a shadow of a doubt. Reverse alignment to standstill could be double checked.)Rating: * * * * *
22. From Newgrange due South over centre of henge P (Martin Brennan. Danny Sullivan shows this line going from the central chamber of Newgrange via its outlying great circle standing stone GC3, but such an alignment over this stone does not correspond to South according to O'Kelly's map; could he have not corrected for magnetic North? Extends in reverse direction as line 1 from Newgrange to henge V. Considered confirmed.)Rating: * * * * *
23. From the cairn (identified as a "barrow" on the OS map) at North East corner of this image through point X, over or very close to cairn U, to tumulus A. (Spotted by me, although the contours of the hill of Dowth would appear to prevent intervisibility between all four points on this line. Unsure of astronomical alignment, if any. Extends in reverse direction as line 5. Alignment and possible astronomical orientation need to be checked in situ.)Rating: * * *
24. From passage of cairn K due South, intriguingly, to position of noon sun on Winter Solstice. (Mentioned by Martin Brennan. This cairn was reburied afer excavation but Brennan said the dig plan shows this alignment to be definite; he also mentions another due South alignment [not shown on this map] from one of the satellite cairns at Knowth; the latter should be investigated and added to this map. Should be re-confirmed from dig plan.)Rating: * * * *
25. From cairn E over Dowth to sunrise at Summer Solstice. (Same as line 8. Assumed by me because this line seems parallel to line 7 on the map. Independently identified by AnneMarie Moroney, Richard Moore and Anthony Murphy, and observed in Summer 2000. Could this be an extension of the line mentionned by Martin Brennan – not shown on this map – which runs in the reverse direction from Dowth to Winter Solstice sunset? )Rating: * * * * *
26. From cairn I over cairn E to Winter Solstice sunset (Martin Brennan. Probably parallel to the alignment from the South passage at Dowth to Winter Solstice sunset – not included on this map – found by Martin Brennan and observed by Anne-Marie Moroney. Considered as confirmed)Rating: * * * * *
27. From mound or henge Q over cairn I and Newgrange. (Noticed by me, unsure of astronomical orientation, if any. Alignment and possible astronomical orientation need to be checked in situ.)Rating: * *
28. From ruined cairns H, G, and F over tumulus E and Newgrange to sunset on the February and November cross-quarter days of Imbolc and Samhain. (Martin Brennan. Considered as confirmed, maybe worth double checking?)Rating: * * * * *
29. From ruined cairn F, G or H over henges R and N. (Noticed by me, unsure of astronomical alignment, if any. Extends in reverse direction as line 12. Alignment and possible astronomical orientation need to be checked in situ.)Rating: *
30. From Newgrange due West to sunset at Spring and Autumn Equinoxes. (Martin Brennan. Need to check out how this line intersects with cairns K and L. Extends in reverse direction as line 15.)Rating: * * * * *
31. From summit of unnamed 104m. hilltop at Eastern edge of map through Western passage of main cairn at Knowth, towards sunset at Spring and Autumn Equinoxes. (Martin Brennan assumed this equinoctial orientation, pointing out the likely shadow cast by a standing stone onto the vertical line on the kerbstone at the entrance to this passage. In their 1997 survey, Tom Ray and Frank Prendergast determined the azimuth of the inner original portion of the Western passage as 278 degrees, i.e. 8 degrees North of due West [with the newer outer portion oriented to 259 degrees, i.e. 9 degrees South of due West], based on a flat horizon. In October 2000, Victor Reijs requested permission from Dúchas to record the solar penetration with a videocam around the Spring Equinox 2001 but had received no reply as of February 2001. I noticed the extension to the hilltop. A priority for investigation. Extends in reverse direction as line 13.)Rating: * * * *
32. From Northern passage of Dowth to sunset at Spring and Autumn Equinoxes. (Martin Brennan. But Anne-Marie Moroney thinks the passage is not aligned due West, and that the sunbeam could have entered it at the cross-quarter days of Bealtaine in early February and Halloween in early November, with a possible alignment with the moon as well. She reports that William Battersby once pointed out to her, as they stood together on the top of Dowth shortly after Christmas, close to the winter sosltice, that the hill behind which the sun sets at that time of year is called Réaltóg, which means "young star" or "small star" in Irish. Needs further checking in situ with precise azimuth).Rating: * * *
33. From Newgrange's outlying great circle standing stone GC2, through the central chamber of the cairn, and thence via its outlying great circle standing stone GC 17, over Knowth to minor lunar standstill (Martin Brennan and Danny Sullivan. Considered as confirmed, but would be good to get precise azimuth for local horizon.Rating: * * * *
34. From tumulus B over Newgrange to sunset at Summer Solstice (Martin Brennan, and confirmed by Richard Moore at the Summer Solstice in 2000. Would be good to get local azimuth.Rating: * * * * *
35. From summit of Redmountain over tumuli E and M. (Noticed by me. Intersects with lines 18 and 19. Unsure of astronomical alignment, if any, but because it has a similar orientation to lines 14 and 17, it might be aligned to minor lunar standstill. Extends in reverse direction as line 17. Alignment and possible astronomical orientation need to be checked in situ.)Rating: * *
36. From tumulus / henge A over Newgrange to major lunar standstill (Martin Brennan. Similar orientation to line 18. Extends in reverse direction as line 21 to Winter Solstice sunrise. Considered certain but would be good to re-confirm in situ.)Rating: * * * *
37. From tumulus or henge W over point X above Mattock river due East towards sunrise at Spring and Autumn equinoxes. (Suspected by me because of apparent intersection of lines 3, 16 and 23 at point X. Extends in reverse direction as line 10. Position of point X and possible alignment and astronomical orientation need to be checked in situ.)Rating: * *
38. From Dowth over tumulus or henge W. (Suspected by me because of similar orientation to lines 33 and 34, with possible alignment to either Summer Solstice sunset or to minor lunar standstill. Astronomical orientation need to be checked in situ.)Rating: * * *
39. From cairn or henge W apparently over edge of cairn H and thence via summit of Redmountain towards Winter Solstice sunrise. (Assumed by me because this line has a similar orientation to line 21 which Brennan identified as being thus oriented. Extends in reverse direction as line 18, perhaps to major lunar standstill. A priority to be checked in situ).Rating: * * *
40. From summit of 104m. hilltop at Eastern edge of map, over henge (or cairn?) S and thence over henge V. (Assumed by me because this line seems has a similar orientation to line 17. Unsure of astronomical alignment, if any. Needs to be investigated in situ. Extends in reverse direction as line 14, which is oriented similarly to lines 33 and 35, possibly to minor lunar standstill.)
3. From unnumbered tumulus at SW corner of the map past edge of main cairn at Knowth either close to or over Cairn T, to sunrise at Summer Solstice. (Suspected by me because this line and its neighbouring line 2 have a similar orientation to line 7, which is said to be thus oriented by Danny Sullivan. Converges with lines 2 and 4 close to a souterrain indicated by a small white dot on the map. Alignment and astronomical orientation need to be checked in situ.)Rating: * *
4. From cairn I due North over point X. (Assumed by me because point X is the apparent intersection of lines 5, 10, and 16; it would be worth having a look around for any evidence of a ruined megalithic site at this location. If my location of point X is inaccurate, the alignment could also be from cairn J (rather than cairn I) due North via point X, beyond which this line converges with line 3 close to a souterrain indicated by a white dot on the map. Alignment and astronomical orientation need to be checked in situ.)Rating: * * * *
5. From tumulus A over or very close to cairn U through point X to the cairn (identified as a "barrow" on the OS map) at North East corner of this image. (Spotted by me, although the contours of the hill of Dowth would appear to prevent intervisibility between all four points on this line. Unsure of astronomical alignment, if any. Extends in reverse direction as line 23. Alignment and possible astronomical orientation need to be checked in situ.)Rating: *
6. From the unidentified cairn near the bend in the Boyne close to the North East corner of the map, due South to the summit of Redmountain. (Assumed by me since the alignment seems accurate and Redmountain – whose summit also lies at the intersection of lines 17 and 18 – is the most prominent hill overlooking whole the Brú na Bóinne area.)Rating: * * *
7. From central chamber of Newgrange via its outlying great circle standing stone GC10 to the Summer Solstice sunrise. (Danny Sullivan. Alignment and astronomical orientation need to be checked in situ.)Rating: * * *
8. From tumulus E over Dowth to sunrise at Summer Solstice. (Assumed by me because this line seems parallel to line 7 on the map. Independently identified by AnneMarie Moroney, Richard Moore and Anthony Murphy, and observed in Summer 2000. Could this be an extension of the line mentionned by Martin Brennan – not shown on this map – which runs in the reverse direction from Dowth to Winter Solstice sunset? ). Rating: * * * * *
9. From Newgrange via its outlying great circle standing stone GC8, over Dowth to minor lunar standstill moonrise North. (Reported by Martin Brennan and Danny Sullivan. The reverse alignment, from Dowth over Newgrange to the minor lunar standstill South was onfirmed during observations by Anthony Murphy, Richard Moore and Raymond Balfe at Dowth on 14 November 2000, when the sunset occurs at the same azimuth as the minor lunar standstill.) Rating: * * * * *
10. From mound W due East through point X to sunrise at Spring and Autumn Equinoxes. (Assumed by me. Alignment and astronomical orientation need to be checked in situ.) Rating: *
11. From Newgrange over cairn I and henge or mound Q. (Noticed by me, unsure of astronomical alignment, if any. Extends in reverse direction as line 27. Anthony Murphy reports that the gaps in mound Q are aligned to the Summer Solstice sunrise. Alignment and astronomical orientation need to be checked in situ. ) Rating: *
12. From henge R over cairn H. (Noticed by me, unsure of astronomical alignment, if any. Extends in reverse direction as line 28. Alignment and astronomical orientation need to be checked in situ.) Rating: * *
13. From Eastern passage of Knowth, apparently over or close to the summit of the unnamed 104m. hilltop on the Eastern edge of the map, to sunrise around Spring and Autumn Equinoxes. (Assumed by Martin Brennan. The penetration of the sunbeam into the Eastern passage can no longer be checked in situ because of the concrete slab – erected by Dúchas and the Royal Irish Academy – which now to block the entrance, but it should be verifiable by matching the Equinox sunrise azimuth with that of the passage [determined by Tom Ray and Frank Prendergast in 1997 as 85 degrees, i.e. 5 degrees North of due East, based on a flat horizon]. This line appears to intersect with line 14 on the hilltop. Alignment and astronomical orientation need to be checked in situ.) Rating: * * *
14. From henge V over henge (or cairn?) S to summit of unnamed 104m. hilltop. (Noticed by me. The OS map refers to site S as an earthwork, whilst M.J. O'Kelly refers to it as a tumulus. Similar orientation to lines 17, 33 and 35, but unsure of astronomical orientation, if any. Appears to intersect on hilltop with line 13 from the Eastern passage of Knowth. Extends in reverse direction as line 40. Alignment and astronomical orientation need to be checked in situ.) Rating: *
15. From Newgrange due East over cairn U to sunrise at Spring and Autumn Equinoxes. (Martin Brennan. This line appears to intersect with the summit of the nearby 95m hilltop above the village of Donore – i.e. Dún Uabhair – [just off the Eastern edge of the map]; curiously, this name means the Fort of Pride or Fort of Merriment in Irish; might this have been a locus for ritual celebration on the Equinoxes? Extends West from Newgrange as line 30. Alignment and astronomical orientation need to be checked in situ.) Rating: * * * *
16. From point X above the river Mattock over edge of mound (or henge) Q to unnamed earthwork at South East corner of the map. (Noticed by me, although the latter henge appears not to be intervisible from henge Q due to the shoulder of Redmountain getting in the way. Unsure of astronomical alignment, if any. Alignment and astronomical orientation need to be checked in situ.) Rating: *
17. From tumulus M over tumulus E to summit of Redmountain. (Noticed by me because it intersects at the summit of this hill with lines 18 and 19, and has an orientation similar to lines 14 and 33. Unsure of astronomical alignment, if any. Extends in reverse direction as line 35 which might be oriented to the minor lunar standstill. Alignment and astronomical orientation need to be checked in situ.) Rating: * *
18. From summit of Redmountain, the highest point in the Brú na Bónne area, apparently over cairn H and henge (or cairn?) W, possibly to the major lunar standstill. (Noticed by me. Possibly aligned to the major lunar standstill because its orientation is similar to line 21, which runs from cairn A over Newgrange and which is thus oriented according to Brennan. Intersects at hilltop with lines 17 and 19. Extends in reverse direction as line 39. Alignment and astronomical orientation need to be checked in situ.) Rating: * *
19. From summit of Redmountain, apparently due North to unnamed cairn near North East corner of the map. (Noticed by me. Intersects with lines 17 and 18. Alignment and astronomical orientation need to be checked in situ.)Rating: * * * *
20. From cairn I, apparently due North to point X above the river Mattock. (Noticed by me. Intersects with lines 5 and 16 at point X, and converges along with lines 2 and 3 close to a souterrain shown by a small white dot East of where these lines meet on the map. Extends in reverse direction as line 3. Alignment and astronomical orientation need to be checked in situ.)Rating: * *
21. From backstone of passage of main cairn at Newgrange over its great circle standing stone GC1 in front of the entrance, and thence over tumulus A to sunrise at Winter Solstice. (Michael J. O'Kelly, Martin Brennan et. al. Extends in reverse direction as line 36 to major lunar standstill. The solsticial alignment is confirmed beyond a shadow of a doubt. Reverse alignment to standstill could be double checked.)Rating: * * * * *
22. From Newgrange due South over centre of henge P (Martin Brennan. Danny Sullivan shows this line going from the central chamber of Newgrange via its outlying great circle standing stone GC3, but such an alignment over this stone does not correspond to South according to O'Kelly's map; could he have not corrected for magnetic North? Extends in reverse direction as line 1 from Newgrange to henge V. Considered confirmed.)Rating: * * * * *
23. From the cairn (identified as a "barrow" on the OS map) at North East corner of this image through point X, over or very close to cairn U, to tumulus A. (Spotted by me, although the contours of the hill of Dowth would appear to prevent intervisibility between all four points on this line. Unsure of astronomical alignment, if any. Extends in reverse direction as line 5. Alignment and possible astronomical orientation need to be checked in situ.)Rating: * * *
24. From passage of cairn K due South, intriguingly, to position of noon sun on Winter Solstice. (Mentioned by Martin Brennan. This cairn was reburied afer excavation but Brennan said the dig plan shows this alignment to be definite; he also mentions another due South alignment [not shown on this map] from one of the satellite cairns at Knowth; the latter should be investigated and added to this map. Should be re-confirmed from dig plan.)Rating: * * * *
25. From cairn E over Dowth to sunrise at Summer Solstice. (Same as line 8. Assumed by me because this line seems parallel to line 7 on the map. Independently identified by AnneMarie Moroney, Richard Moore and Anthony Murphy, and observed in Summer 2000. Could this be an extension of the line mentionned by Martin Brennan – not shown on this map – which runs in the reverse direction from Dowth to Winter Solstice sunset? )Rating: * * * * *
26. From cairn I over cairn E to Winter Solstice sunset (Martin Brennan. Probably parallel to the alignment from the South passage at Dowth to Winter Solstice sunset – not included on this map – found by Martin Brennan and observed by Anne-Marie Moroney. Considered as confirmed)Rating: * * * * *
27. From mound or henge Q over cairn I and Newgrange. (Noticed by me, unsure of astronomical orientation, if any. Alignment and possible astronomical orientation need to be checked in situ.)Rating: * *
28. From ruined cairns H, G, and F over tumulus E and Newgrange to sunset on the February and November cross-quarter days of Imbolc and Samhain. (Martin Brennan. Considered as confirmed, maybe worth double checking?)Rating: * * * * *
29. From ruined cairn F, G or H over henges R and N. (Noticed by me, unsure of astronomical alignment, if any. Extends in reverse direction as line 12. Alignment and possible astronomical orientation need to be checked in situ.)Rating: *
30. From Newgrange due West to sunset at Spring and Autumn Equinoxes. (Martin Brennan. Need to check out how this line intersects with cairns K and L. Extends in reverse direction as line 15.)Rating: * * * * *
31. From summit of unnamed 104m. hilltop at Eastern edge of map through Western passage of main cairn at Knowth, towards sunset at Spring and Autumn Equinoxes. (Martin Brennan assumed this equinoctial orientation, pointing out the likely shadow cast by a standing stone onto the vertical line on the kerbstone at the entrance to this passage. In their 1997 survey, Tom Ray and Frank Prendergast determined the azimuth of the inner original portion of the Western passage as 278 degrees, i.e. 8 degrees North of due West [with the newer outer portion oriented to 259 degrees, i.e. 9 degrees South of due West], based on a flat horizon. In October 2000, Victor Reijs requested permission from Dúchas to record the solar penetration with a videocam around the Spring Equinox 2001 but had received no reply as of February 2001. I noticed the extension to the hilltop. A priority for investigation. Extends in reverse direction as line 13.)Rating: * * * *
32. From Northern passage of Dowth to sunset at Spring and Autumn Equinoxes. (Martin Brennan. But Anne-Marie Moroney thinks the passage is not aligned due West, and that the sunbeam could have entered it at the cross-quarter days of Bealtaine in early February and Halloween in early November, with a possible alignment with the moon as well. She reports that William Battersby once pointed out to her, as they stood together on the top of Dowth shortly after Christmas, close to the winter sosltice, that the hill behind which the sun sets at that time of year is called Réaltóg, which means "young star" or "small star" in Irish. Needs further checking in situ with precise azimuth).Rating: * * *
33. From Newgrange's outlying great circle standing stone GC2, through the central chamber of the cairn, and thence via its outlying great circle standing stone GC 17, over Knowth to minor lunar standstill (Martin Brennan and Danny Sullivan. Considered as confirmed, but would be good to get precise azimuth for local horizon.Rating: * * * *
34. From tumulus B over Newgrange to sunset at Summer Solstice (Martin Brennan, and confirmed by Richard Moore at the Summer Solstice in 2000. Would be good to get local azimuth.Rating: * * * * *
35. From summit of Redmountain over tumuli E and M. (Noticed by me. Intersects with lines 18 and 19. Unsure of astronomical alignment, if any, but because it has a similar orientation to lines 14 and 17, it might be aligned to minor lunar standstill. Extends in reverse direction as line 17. Alignment and possible astronomical orientation need to be checked in situ.)Rating: * *
36. From tumulus / henge A over Newgrange to major lunar standstill (Martin Brennan. Similar orientation to line 18. Extends in reverse direction as line 21 to Winter Solstice sunrise. Considered certain but would be good to re-confirm in situ.)Rating: * * * *
37. From tumulus or henge W over point X above Mattock river due East towards sunrise at Spring and Autumn equinoxes. (Suspected by me because of apparent intersection of lines 3, 16 and 23 at point X. Extends in reverse direction as line 10. Position of point X and possible alignment and astronomical orientation need to be checked in situ.)Rating: * *
38. From Dowth over tumulus or henge W. (Suspected by me because of similar orientation to lines 33 and 34, with possible alignment to either Summer Solstice sunset or to minor lunar standstill. Astronomical orientation need to be checked in situ.)Rating: * * *
39. From cairn or henge W apparently over edge of cairn H and thence via summit of Redmountain towards Winter Solstice sunrise. (Assumed by me because this line has a similar orientation to line 21 which Brennan identified as being thus oriented. Extends in reverse direction as line 18, perhaps to major lunar standstill. A priority to be checked in situ).Rating: * * *
40. From summit of 104m. hilltop at Eastern edge of map, over henge (or cairn?) S and thence over henge V. (Assumed by me because this line seems has a similar orientation to line 17. Unsure of astronomical alignment, if any. Needs to be investigated in situ. Extends in reverse direction as line 14, which is oriented similarly to lines 33 and 35, possibly to minor lunar standstill.)
REFERENCES:
Brennan, Martin; The Stars and the Stones: ancient astronomy in Ireland; Thames and Hudson, London, 1973. ISBN: 0-500-01295-4. (See map of external design plan of Newgrange on page 71.)
Moroney, Anne-Marie: Dowth, winter sunsets. Flax Mill Publications, Drogheda, 1999. ISBN: 0 9533822 3 0. (See page 11.)
O'Kelly, Michael J. Newgrange: archaeology, art and legend. Thames and Hudson, London, 1982. ISBN: 0-500-27371-5. (For identification of outlying great circle standing stones, see general plan of Newgrange on page 15.)
Sullivan, Danny; Leys. Wooden Books, Powys, Wales, 2000. ISBN: 1 902418 20 4. (See diagram of Boyne Valley Leys on page 43.)
Brennan, Martin; The Stars and the Stones: ancient astronomy in Ireland; Thames and Hudson, London, 1973. ISBN: 0-500-01295-4. (See map of external design plan of Newgrange on page 71.)
Moroney, Anne-Marie: Dowth, winter sunsets. Flax Mill Publications, Drogheda, 1999. ISBN: 0 9533822 3 0. (See page 11.)
O'Kelly, Michael J. Newgrange: archaeology, art and legend. Thames and Hudson, London, 1982. ISBN: 0-500-27371-5. (For identification of outlying great circle standing stones, see general plan of Newgrange on page 15.)
Sullivan, Danny; Leys. Wooden Books, Powys, Wales, 2000. ISBN: 1 902418 20 4. (See diagram of Boyne Valley Leys on page 43.)