Essen, horizontal view

Internet Project

Observing, Photographing and Evaluating the

Transit of Venus, June 8th, 2004

Essen, equatorial view

Tips and Instructions for the Transit Day

This project's aim is to determine the distance to the Sun by comparing the positions of Venus on pictures which have been simultaneously taken from different sites on Earth. For this reason, it will be necessary to take photos with precisely known orientation at exactly concerted moments at as many sites as possible.

The basic ideas and an evaluation example are again described in additional pages.

In principle, two simultaneously taken photos are enough to determine the distance to the Sun. However, our experiences made during the transit of Mercury last year have shown us that the errors which are due to bad focussing, the process of digitizing, the measured positions etc. make it impossible to get a satisfying result on the basis of two only photos. Therefore, as many pictures as possible should be combined in order to minimize random errors by statistical methods.


The participants are asked,

Tips for Photographing

Position measurements

There exist several tools for measuring the positions of Venus with respect to the Sun's face. In this project, we offer the program Bildauswertung.exe. It is contained in the zipped archive. With that program, the sizes and positions of Sun and Venus on digitized pictures (BMP or JPG format) can be measured by fitting to them circles of variable size and position.

Additional measurements during the transit

back to the main page

Udo Backhaus
last modification:  March 28th, 2008