Methods for using the bearing dial.

Following experiments are made with the bearing-dial placed directly in the sun. The sunrays will be parallel in reality with the correct distance to the sun.
When changing latitude, time of the day or date of the year, the sunheight or the location of the sunshadow will change.

The sunheight - the angle to the sun - can be expressed from the sunshadow.

When sailing N-S determining the latitude.

Measuring sunheights during the day for calendarpurposes.

Measuring the amplitude at sunrise and sunset for latitudeobservations. Especially the daymarks, sunrise, dagmala, noon, eykt and sunset were used measuring sunheights.

 

Measurement 1.

Copenhagen (55,4N) 21'th of December 2001 (decl. app. -23.50, sunhight at noon = 11,4 dg.)

Bearing the sun at noon at wintersolstice throws a shadow shown on the picture. The straight edge (lower) on the bearing dial is a scale for latitudes measured in the winterseason. Going south will make the shadow moving towards the centre of the inner circle. Going north to 60N will make the shadow pointing near the outer circle.

Measurement 2.

Copenhagen (55,4N) 21'th of January 2002 (a month later)

Bearing the sun at noon the 21'th of January moves the shadow towards the center (re.: measurement 1). The same shadow will be thrown from a latitude app. 51,5N by noon at wintersolstice. But the scratches on the disk indicates that the Vikings could manage this problem with four variables (latitude, azimuth, sunhight and time of the year)

 

Measurement 3.

Setting a course with an external gnomon shows how accurate measurement can be done with the dial. The straight edges are carved after a special geometrically method. For more details click here.

Note: Carved or broken?

Its obvious that the straight lower edge is carved - not broken. The little split is carved for calibrating purposes. Click here for more info.

The same tendency for the upper edge. Its carved - not broken.

It proves that Captain Solvers reconstruction isn't correct. For more details click here.

 

The above experiment will be repeated for more accuracy and examples.

Any comments to Erik Torpegaard eti@ddf.dk