A convenient way to mark the center of the sun's image made in a reflected ceiling dial is as follows. Punch a hole approximately 1 mm in diameter in the center of a 3" x 5" file card. Hold the card in the beam of reflected sunlight a few inches from the ceiling. Adjust the card perpendicular to the beam to get a circular image of the sun with the pinhole centered in the image. The light coming through the pinhole will indicate very closely the desired point on the ceiling. Mark this point and label it with the appropriate time and/or date. The accuracy of this method depends on how accurately you can hold the pinhole in the center of the circulate image of the sun. I can get consistent results within about 10 seconds.
A convenient way to mark the center of the sun's image made in a reflected ceiling dial is as follows. Punch a hole approximately 1 mm in diameter in the center of a 3" x 5" file card. Hold the card in the beam of reflected sunlight a few inches from the ceiling. Adjust the card perpendicular to the beam to get a circular image of the sun with the pinhole centered in the image. The light coming through the pinhole will indicate very closely the desired point on the ceiling. Mark this point and label it with the appropriate time and/or date. The accuracy of this method depends on how accurately you can hold the pinhole in the center of the circulate image of the sun. I can get consistent results within about 10 seconds.
