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How is Rock Art aged?
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Evergreen Dazed
Evergreen Dazed
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Re: How is Rock Art aged?
Dec 19, 2012, 15:15
tiompan wrote:
Evergreen Dazed wrote:
tiompan wrote:
Evergreen Dazed wrote:
tiompan wrote:
Evergreen Dazed wrote:
tiompan wrote:
Evergreen Dazed wrote:
tiompan wrote:
Evergreen Dazed wrote:
tiompan wrote:
Evergreen Dazed wrote:
tiompan wrote:
Evergreen Dazed wrote:
Tiompan, do you know if the 'hoof marks' at Cothiemuir are bona fide? They seem odd, being on the outer face of the recumbent.


I'm confident they are natural .


So the stone was perhaps selected, do you think? Its some coincidence that they are located where the moonset can be viewed. (But then again, obviously not visible if observing from the centre of the circle)


Possibly the reason it was chosen . The main thing about Cothiemuir and most other recumbents is that the low summer moon can be seen to move between the flankers as seen from (roughly ) the centre of the circle .
If you move a bit from the centre in any direction the phenomenon will still be much the same . It's the recumbent as a whole that is the "screen" and a small unseen spot on the outside of the recumbent has no impact orientationwise .


And yet.. if there was no importance orientation wise, and if the stone was selected, as suggested, because of the natural marks, why not turn the recumbent round and have them facing inwards and visible to the observer?

Even though the marks are not visible to the observer as they are, it seems they chose to put them in a certain place, that being the area of the moonset?



It can be the the point of the moonset at very particular time ,and not necessarily auspicious ,importantly it depends where you are observing from . How does the observer know where that particular spot is ? move a metre and the orientation is out . How do you see the other marker which is hidden from view ?


Of course, very problematic. "I don't know" is the answer, sadly.
I have visited, but can't remember, whereabouts is the cist?

Just posting this again in case it was missed :

Its summit [the recumbent] is relatively even, rising gently towards the E, and on the outer face there are at least two possible cupmarks, situated to the W of the natural indentations known as The Devil’s Hoofmarks
(Canmore)

So genuine(?) cupmarks on the outer face, as well as the natural marks?

Also, if we are talking 'drama' (and who can say we aren't?) it could be aan area for a person or persons to stand, perhaps to be illuminated at that moonset time, 'callanish' style.

Fanciful, that one, I grant you!



I don't think there is anything going for the "hoof mark "moonset idea to be honest .
There was a roughly central ring cairn . There is a slab of rock in the middle but whether prehistoric ? , possibly not .
There are examples of rock art and cup marks on recumbents no doubt about that ,those at Cothiemuir are "possibles " i.e. not that convincing/difficult to be sure .
Drama , why not . But when you think of other monumnets that have astro alignments like passage graves , punters in the passage acting dramatically or even being there is unlikely , maybe what matters is the alignment itself .


Aye, I do see your point. When you look at somehwere like Balnuaran it is hard to imagine a writhing initiate in the path of the setting midwinter sun!

A great subject though. I'd like to look a little deeper into alignments. Do you know of a good site/software for azimuths/declination and general info? Do you use landranger maps to calculate yr declinations for rising/setting sun, for example?

Bear with me here, but if i'm looking along one stone, an outlier for arguments sake, to another, say NW, I guess its a compass bearing, then checking the horizon height via maps? And once you have that, using it to get the declination of (for this example) the rising sun at that point?

If youre willing to share a bit of info on methods, i'm listening!




A good starting point is Ruggles "astronomy in Briatain etc " 1999 .
One difficulty is understanding the concept of declination ,if you already do so then that's a big step forward .
Burl , Ruggles and Thom all used maps for their calc at many sites , not all by any means , others were surveyed in the field , but there are problems relying solely on maps e.g. grid north is not true north etc .
Having said that we are not dealing wih extreme accuracy in the sites so being a little out might not hurt but we should attempt to be as accurate as possible at our end of the calc .
Basically get an accurate as possible alignment between the two markers , compass is ok but in some respects not as good as a large scale map , if the markesr are visible on GE even better . The accuracy will depend on how close the two ppoints are to each other ,if they are close say 2-10 metres apart there is much more room for error i.e. width of the markers etc ,the greater the distance the greater the accuracy . Then as you say continue to the horizon then calculate the alt from the site to the horizon and include in the dec formula , including refraction and parallax (only for the moon ) to provide a more accurate figure . If tht doesn't make sense , do ask and i'll re-explain.
Was that a Fraserian "I'm listening " ?


Thanks a lot Tiompan, a lot to be going on with there.
No, it wasn't a fraiser thing!

Declination, to me, simply means the measurement of an objects point in the sky at any time. Angle from the ground? I'm sure thats probably wrong.


Declination is a bit more complicated . It's the crux in many repsects .
It's a figure derived from the latitude of the observer , the alt of the horizon and the azimuth of the orientation all bound in a formula .
When the resulting figure corresponds to those known at solstices ,major standstills etc , the event will take place on the horizon .


Ok, I see. So if you were interested in a summer solstice alignment, for example, and yr site has a stone a few degrees east of the known horizon event, but there is an elevated horizon, you might suspect a possible alignment (again just for arguments sake) how would you calculate where the sun will first be visible?

I'm probably approaching that the wrong way, but hope it makes sense.


I may have misunderstood but if the declination works out at the right figure for a solstice at the time of build i.e. 2500 BC would be -24 or +24 degrees of declination , then the sun would have risen or set at the point calculated on the horizon (the horizon would have been already taken ito account in the calculation of the declination ) in 2500 BC , today would be slightly different at -23.45 and +23.45 .
What people often get wrong is assuming that because of the old saw ,"the sun rises due east at equinox " which is true if you live on a boat on the ocean or a with a flat horizon to the eat but if you live in a sttep sided valley or have a wall in front off you the sun won't rise due east but south of east as it has had to rise to get seen over the hill or wall .


I think I need to spend some time going over this until I feel i've got a decent understanding.
Thanks a lot Tiompan, much appreciated.
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