Sundials and their characteristics

If one wants to compare ancient sundials with present sundials a few things need to be relaxed perhaps to compare the characteristics of present day sundials. This page wants to separate the characteristics (for each type of sundial) and than check these characteristics against ancient (neolithic) radials combinations, which might be representing sundials.
A statistical study could be done if radials map sundials and I assume that this will provide a large correlation (like done in studies where megalithic art motifs are compared with posphenes), but I doubt if that is the way forward. I think that the coorelation of functional characteristics of radials and sundials might reveal more.

What neolithic people might have known

It is assumed that neolithic man would have known something about the celestial pole (by watching the night sky) and thus also something about north (and then perhaps south) and they might known something that is close to east and west as being halfway (in days or angle) between north/south or solstice suns sets/sets.
In case neolithic people had a concept of azimuth and perhaps of declination; then perhaps the neo-hour lines in the radials could be azimuth lines. This would be inline with the statement of D. Price (Vistas in astronomy, Vol 9, page 4, 1968):
"One cannot well avoid the suggestion that the chief function of the sundial in antiquity was not the determination of the time of the day, but season of the year."

What neolithic people might not have known

A few things we experience nowadays due to our capacity to measure time without the sun, were perhaps not known in neolithic times:

local mean time (standardized time)
The difference between local apparent and local mean time (equation of time) is maximum in the order of 15 minutes, it is assume this time difference was not measurable in neolithic times and even not known as a concept (for this one needs a standardization body).
duration of a neo-hour
The likely hood that neolithic people had a fix duration Hours during the year is small. There are many cultures where the hour duration depended on the season. But a day (defined as sun rise to sun set) could have been divided a a number of neo-hours.
analemma
For the same reason as the there standardized time, the analemma represented as a figure of 8) was not recognized in neolithic time. But they might have recognized this one, certainly needed for analemmatic sundial.

Different types of likely sundials

Several different sundials exist in present times. Because all radials have lines and dots which seem to be repeating objects to indicate possible neo-hours, the following sundials (Waugh [1973]) have also some of these prominent characteristics:

horizontal sundial
The (neo-)hours lines are not equally spaced, the gnomon is in present day directly towards the celestial pole and the shadow is on a (more or less) horizontal plane. The (neo-)hour lines can be laid our in more then a half circle.
lines of declination
A tip of a gnomon (directed towards the celestial pole) casts the shadow path during the day of equal declination (horns of solstice picture). The shadow plane is normally in horizontal plane.
For me this sundial type is an obvious (and easy to construct) candidate for Neolithic monuments, but it seems not yet to be found!
perpendicular style
The perpendicular/vertical style ends where the gnomon of a horizontal sundial would be (nodus). The shadow is on a (more or less) horizontal plane.
vertical sundial
The (neo-)hours lines are not equally spaced, the gnomon is in present day directly towards the celestial pole and the shadow is on a (more or less) vertical plane. The (neo-)hour lines are in a half circle.
Mass and monastic sundials are part of this family of sundials.
noon mark
De vertical line (gnomon) that provides information when it is noon (local time). The shadow can be on any plane.
I think this is a less likely recognizable type of sundial in neolithic time.
analemmatic sundial
This sundial has no hour lines but hour points, the gnomon is vertical and the shadow of the tip of the gnomon is normally in horizontal plane. The Foster-Lambert sundial is a type of analemmatic sundial (but the gnomon is not vertical).
Foster-Lambert sundial
Comparable to the analemmatic sundial except that the gnomon is directed halfway vertical and the celestial pole.
equatorial sundial
The Hours lines are spaced equally over the day (15 degrees) and has two sides (winter and summer side). The gnomon is directed towards the celestial pole and shadow is on a plane that is parallel to the earth's equator. This sundial does not work on equinox day.
I think this is a less likely type of sundial in neolithic time.

Further sundial characteristics

The three dots (at the top of K-K7) could be the positions for the stylus at winter solstice, equinox and summer solstice like for a Foster-Lamber sundial.
If radials are only in a half circle, this could be a sundial with a vertical shadow planes (zero altitude). If a horizontal shadow plane one would expect radials in a larger part of a circle (early and late hour's relaled azimuth).

Radials and sundials

The radials found in megalithic art might be comparable to more modern sundials. Some examples:

Code	More modern	Type of sundial
L-CairnH	Clogher, Co. Tyrone	early monastic sundial
K-K7	might be modern by itself! Althought M. Brennan ([1983], page 159) thinks it is megalithic art	has something of a analemmatic sundial, like a Foster-Lambert dial?.

Feedback gotten

Tony Wood

"Pattern K-K7 is very reminiscent of mass dial forms. There are eight divisions in the semi-circle, mass dails usually have twelve, but ten and eight are not unknown.

N-K88a and N-88b have eight dots, but don't seem to be like any common mass dial form.

...

There are one or two known mass dials with radial lines of dots but they are certainly rare.

Current verdict on radials as 'sun dials' - Not Proven"

Victor Reijs
"I have the idea that K7 at Knowth Site 1 is more modern then the art on the other stones at Knowth; was this done during a later phase of the habitation at Knowth? The whole carving has a different feel (too straight lines and different pecking). I asked Prof. G. Eogon this question (no responce yet)"
Mario Arnaldi (The Ancient Sundials of Ireland' , The British Sundial Soc., 2000, ISBN 0 95 18404 2 8):

"....Of particular interest are the decorations which cover kerb stones SE4

and NE4

.... Kerb stone SE4, erroneously called the sundial stone has carved on it a radial design, with an eastern central hole greatly resembling a sundial. There is a theory, which I agree with, which sees in this design the central idea of a calendar, probably functioning with the aid of a gnomon. In effect the face of the stone on which the decoration is found is facing east and it makes it difficult to think of a true sundial, but the design on NE4 seems more likely. This kerb stone records on its upper face a similar radial design with three holes for the possible location for a gnomon. The design is very similar to a sundial. And moreover is exactly positioned to allow a hypothetical vertical rod to cast its shadow on the temporal lines.... It is too easy to recognize in the design a sundial, very similar to others which gave the time, in use in the early Middle Ages. In reality we still do not know if this was used for telling the time or not, and it is impossible now to say if we are dealing with an original carving..."

Your opinion is welcome, please send it to me.

Acknowledgments

I would like to thank the following people for their help and constructive feedback: Michael Harley and Tony Wood and all unmentioned other people. Any remaining errors in methodology or results are my responsibility of course!!! If you want to provide constructive feedback, let me know.

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Major content related changes: Jan 9, 2008