CIPA 2003 XIX 11 ' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Picture 1. The flat marble stone.
This stone is placed under the dome, on the main axis of the
church (figure 2). The inscribed line has a length of 70 cm and
seems to indicate something, so its orientation was examined.
The derived astronomical azimuth of this line is 70°35' ± 20'.
The main axis of the chapel of Saint John the Baptist, defined
by the middle of the Altar and the middle of the central window
where the light enters, was also examined. This axis has the
same orientation as the main axis of the church of “the
Transfiguration of our Lord”.
3.4 Determination of the perceptible horizon
The perceptible horizon of a monument is of high importance
because it permits, or restricts, the view of the Sun and the
entrance of the sunlight in the holy altar. It is defined by natural
terrain, mountains, rocks, and sea or by buildings that already
existed at the time of construction of the monument.
AZIMUTH(degrees)
Figure 3. The diagram of the perceptible horizon towards the
East
Measurements of azimuth and altitude of characteristic points
permit the creation of the diagram of the perceptible horizon.
The measurements were done from a point of the network in
front of the Altar. It is indispensable that all these measurements
refer to the middle of the Altar, so that the drawing of the
perceptible horizon corresponds to the view of the horizon from
the Altar.
The eastern horizon of the church is at a mean distance of
1000 m and the determination of its diagram was done with an
accuracy of 2 arcminutes, due to pointing uncertainties. The
adjustment was easily calculated, since the coordinates of the
points of the horizon, the network points and the altar were all
known from the geodetic network and the digital plan of the
church. The diagram of the view of the perceptible horizon to
the east of the church is presented in figure 3. The x-axis shows
the azimuth and the y-axis the altitude (in degrees and grads) of
the horizon.
Picture 2 is the photographic documentation of the horizon.
Picture 2. Photographic panorama of the eastern part of the
horizon
3.5 Determination of the path of the sun
The determination of the apparent diurnal path of the Sun, as
seen from this monument and for a given date, was done using
the SkyMap Pro 8 software (digital almanac & virtual
planetarium, Marriot (2001)). Necessary input data are:
- The astronomical coordinates , A of the church (determined
with satisfactory accuracy from the GPS measurements of the
geodetic network).
- The date (any date between 4713 BC and 8000 AD) and the
time interval between successive points of the position of the
Sun in the sky.
A local ephemeris of the Sun was produced, listing altitude and
azimuth of the Sun, accurate to about 2 arcseconds (Meeus,
1991), as a function of local time.
The church of the "Transfiguration of our Lord" celebrates on
August 6 th and the chapel of Saint John celebrates on January
7 th each year. As already mentioned, the first building was
erected in 1360 and contained the holy altar of today and the
chapel. The extension of the building was done in 1388.
Therefore, the calculation of the path of the Sun was made for
these particular dates and years.
Figure 4 combines all available data, showing the path of the
Sun and the azimuths of the examined lines superimposed on
the diagram of the perceptible horizon. The rectangular insets in
the figure show, in magnification, the intersection of the three
characteristic lines and the resulting accuracy of the orientation.
AZIMUTH (deg rees)
Figure 4. The diagram of the perceptible horizon towards the
East and the apparent paths of the Sun
The combined error of the orientation of the main axis,
represented by the dark area in the middle of the inset, is about
V.2 and the combined error of the orientation of the line
inscribed in the flat marble stone is about 20', due to its short
length. The magnitude of the combined errors depends on the
errors of the azimuth of the lines, of the path of the Sun and of
the line of the perceptible horizon.
4. DISCUSSION
As it is apparent from the diagram in figure 4
