Venus will enter and leave the Sun at slightly different times, if observed from different parts of the world. Measurements of these times make it possible to calculate the distance from the Earth to the Sun.
In this activity you have to register and share our observations done June 6.
The measurements must be performed using an astronomical telescope. You will need:
Use high magnification, but not so high that the image of the Sun becomes very blurred due to turbulence in the air.
Monitor the Sun extra closely from a few minutes before Venus enters the solar disc, until the entire planet is inside the solar limb. You should also monitor the Sun from a few minutes before Venus starts to leave the Solar disc, until the entire planet is free of the Sun.
Measure the time for these four contact points as accurate as you can. The most important ones are the time for second and third contact.
The calulus itself is a pretty complex matter, so we shall not dwell with it here. Register your observation. Combined with observations from another location you can use our application to calculate the distance to the Sun.
During a Venus transit, and especially in the beginning and end, several most exciting phenomena will occur. These phenomenae will however make it more difficult to obtain accurate timings.The black-drop effect: The black-drop effect may become visible when Venus enters or leaves the solar disc. The enormous brightness difference between the dark side of Venus and the intrinsically bright solar disc causes Venus to apparently merge with the solar disc. When Venus, according to the calculated time tables, should be outside the solar disc, it may instead appear to "be stuck" in the Sun's limb. You may create your own black-drop effect by bringing two fingers gradually closer to each other, while at the same time having a bright object in the background. It should then look as the two fingers meet before the actually do.
|The black drop effect begins when Venus has moved into the solar disk.||The black drop effect should gradually become more evident as Venus enters the solar disk.||The black drop effect should be easiest to observe when all of Venus has entered the solar disk.|
|Before 2nd contact||Before 2nd contact||2nd contact||After 2nd contact|
Exercise 2: Measure the distance to the Sun
- Method A: Timing Venus' entrance and departure on solar disc
- Method B: Drawing Venus' path across the solar disc
On www.astroevents.no there is more information about the Transit of Venus and other celestial events.
The project The earth and the sun focusing on the spectacular celestial events 2010–2015.
This website, other communication and national initiatives linked to celestial events is made possible by funding from DnB NOR Savings Bank Foundation.
Astronomer Knut Jørgen Røed Ødegaard was head of the project.