European Southern Observatory (ESO)European Association for Astronomy Education (EAAE) Observatoire de ParisInstitut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE)Astronomical Institute of the Academy of Sciences of the Czech Republic The Venus Transit 2004 European Science & Technology Week 2004Visit the websites of the VT-2004 organisers

The Venus Transit 2004

... Educational Sheet 2

Appendix 2

Building a "Horizontal angle measurer"

This is a very simple tool to measure horizontal angles (angular distance) between two remote objects. The results are fairly rough, but using the instrument makes the principle easily understood.

Make a copy of the angle measurer for each student. The tool will work best if you make a photocopy on a piece of A4 cardboard.

The instrument consists of two parts:

  • a base plate divided into degrees and
  • a movable pointer.

Assemble the angle measurer following the instructions:

  1. Cut out both parts.
  2. Cut and remove the interior of the small window in the pointer.
  3. Fold the arrows on the base plate and on the pointer until they are perpendicular to the base.
  4. Connect both parts with a split pin in the centre of the grey spots, so the pointer can turn around the centre point of the grey spots.

The instrument has to be used on a firm horizontal surface, e.g. a table. When you want to measure the angle between two remote markers, put the eye arrow and the reference arrow in line with the first marker. Keeping the base in this position, turn the pointer until you see the eye arrow and the target arrow in line with the second marker. Now you can read the angular distance between the two markers from the scale.

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