In the weeks after the transit several images have been uploaded or submitted to U. Backhaus. The corresponding worksheets with Venus positions have been uploaded via our data exchange page. By evaluating these lists of position measurements with the program comptransitpos you can, for instance, get the following visualisations:
|Arnsdorf positions||Canberra positions||SDO positions|
Comparison of the extrapolated contact times with those calculated by the USNO transit computer will show that the measured positions produce quite good line fits; most of the times differ from the calculated values by some seconds only!
Comparisons between these positon data within the same program yield the following results:
The following table summerizes the values of the solar parallax which can be determined by evaluating the uploaded lists of Venus position data.
|Results for the solar parallax|
It is difficult to estimate the errors of these measures. Therefore, they are given without variance. Perhaps, they will be rated later.
Additionally, it is possible to compare single pictures which have been simultaneously taken at distant sites by using the worksheet comp2Venuspositions. In this way you can get very excellent results for the Astronomical Unit by comparing pictures made by our participants especially with those of the SDO spacecraft. This success is due to the long baseline between the "observers" and the corresponding large parallax effect.
In many cases, however, even the comparison between Earth made images is quite satisfying. In the case of bad parallax results possible reasons may be
The following images from Canberra, Australia (S. Bolton), Tromsø, Norway (J. Trebs), Usedom, Germany (A. Hänel) and Arnsdorf, Germany (E. Merker) may be regarded as a challenge
|original 1||original 2||combination||resulting solar parallax|
|1. Usedom 3:00:01 UT
2. Canberra 3:00:11 UT
|1. Usedom 4:29:30 UT
2. Canberra 4:29:32 UT
|1. Usedom 4:40:10 UT
2. Canberra 4:40:07 UT
|Tromsø 3:12:15 UT
Canberra 3:12:16 UT
|Arnsdorf 4:21:49 UT
SDO 4:21:48 UT
|Rügen 3:59:18 UT
Hawaii 4:01:56 UT
|Arnsdorf, 4:00:30 UT||Canberra 4:00:02 UT||SDO 03:59:59 UT|
The evaluation is done in four steps:
|Arnsdorf||β=85.4° ⇒ α=36.0°|
|Canberra||β=76.2° ⇒ α=26.8°|
The parallax of Venus can be made visible by the following steps:
|Arnsdorf-Canberra ...||... and the corresponding daylight side of the Earth|
Only Andreas Hänel partly followed our suggestions to take "twice exposured pictures". The worksheet in our database contains a preliminary evaluation of some of his pictures. The following picture (produced with comptransitpos) visualizes the result.
For the uploaded single exposure pictures the orientation is not given. However, because at transit time there are some prominent sunspots on the sun's surface it may be possible to find the orientation by comparing the pictures with professional images taken at nearly the same time. We use for this idea the images taken by NASA's Solar Dynamics Observatory. Pictures of which we saw first as Astronomy Picture of The Day. NASA published related videos and the complete full size images, too.
Because this observatory circuits on a geosynchronous orbit its distance to the Earth's center is quite large and therefore it generates a large parallaxe effect. In order to compare project photos with SDO photos exact timing and position data must be known. We will describe the detailed procedure later. For today, the interested reader may use the worksheet containing time and position data. A slightly adapted version of comp2Venuspositions.xls can be found in our stuff page.
In this way we first found the orientation of the images taken bei T. Häusler in Hawaii and could then measure the positions of Venus on them.
Finally, it was possible to combine pictures of A. Hänel and T. Häusler with those of SDO - with (for the first attempt) quite satisfying results!
|Observer||combined picture||resulting solar parallaxe|
||last update: 07.12.2012|