The main goal of this project was to visualize the parallax effect of Mercury that means the fact that during its transit Mercury is found at slightly different positions on the solar disc when it is observed from distant places on Earth at the same time. The effect was to be proved by taking simultaneous pictures of the transit and by combining those pictures later. For this reason, a platform was offered for sharing own images of the transit with participants all over the world.
We got pictures from 23 sites, mainly in Europe but, fortunately, in Southern Africa and Southern and Northern America, too.
| Hannover, Germany - SDO, Orbit
| Lippstadt, Germany - IAS, Namibia
| Geseke, Germany - Rosario, Argentina
| Rosario, Argentina - Pointe Saint Mathieu, France
The second goal was not only to visualize the parallactic effect but also to measure its size. Therefore, the orientation of the images had to be determined very precisely. Only very few participants used the method of taking "double exposed" pictures. Fortunately, on transit day the Sun showed a prominant group of sunspots which allowed another (but less sensitive) determination of the Sun's orientation on the images. Some of the uploaded pictures are sufficiently simultaneous and allow direct comparisons, that means precise combinations and measurements of Mercury's positions with respect to the same direction of reference. With the precisely measured positions the solar parallax can be derived by using the method described in the project page Example and in the additional paper (English version and German version).
Some of the most satisfying combinations of single and the results of their evaluation are the following:
|Superposition||Resulting solar parallax|
|Caracas, Venezuela - Lippstadt, Germany
(E. Torres/R. Schünecke)
|Caracas, Venezuela - Hannover, Germany
(E. Torres/U. Backhaus)
|IAS, Namibia - Hannover, Germany
(R. Anton/U. Backhaus)
|IAS, Namibia - Lippstadt, Germany
(R. Anton/R. Schünecke)
|Hannover, Germany - Big Bear Lake, California
(U. Backhaus, G. Schneider/J. M. Pasachoff)
|Cologne, Germany - Big Bear Lake, California
(M. Junius, G. Schneider/J. M. Pasachoff)
|Bochum, Germany - Caracas, Venezuela
(A. Knülle-Wenzel, E. Torres)
The mean solar parallax of the comparisons between these selected pictures from two distant sites is πS=8.9"±0.4".
The third goal of this project was to derive the distance to the Sun, i. e. the solar parallax, as exctly as possible.
The central task for this goal is the determination of the images' orientation. As stated above, this task is difficult and the final
results depend from measurement errors very sensitively.
One possibility of proving not only the quality of the images but also that of the determination of the orientation is to compare the measured positions of Mercury with those measured on the SDO images.
|Superposition||Measured positions||Determination of the solar parallax|
|Big Bear Lake, California
(G. Schneider/J. M. Pasachoff)
(Astron. Gesellschaft, Greiz)
|Pointe Saint Mathieu, France
By integrating all these comparisons of the uploaded series of pictures with the SDO series we attain a very satisfying result:
|The mean solar parallaxes of these comparisons are||πS=9.22"±0.15"||(measured values)|
Because of the much shorter baselength parallax measurements from Earth respond even more to errors of the position measurements. Therefore, not all of the possible comparisons between series of Earth-bound transit images yield acceptable results. The best of them are presented below:
|Measured positions||Determination of the solar parallax|
|Big Bear Lake, California
|The mean solar parallaxes of these comparisons between two distant sites are||πS=8.2"±0.5"||(measured values)|
||last update: 2019-01-25|