Distance to the Sun using Venus transit

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Discussion Overview

The discussion centers on calculating the astronomical unit (1 AU) using data from a Venus transit, specifically seeking methods that do not rely on the parallax technique. Participants explore the feasibility of using a single observation from the 2012 transit and discuss the implications of angular measurements during the transit.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks a method to calculate 1 AU from a single observation of the Venus transit, without using the parallax method.
  • Another participant references Halley's method, suggesting it involves timing the transit from different locations on Earth, which aligns with the parallax approach.
  • A participant expresses uncertainty about how to account for angular differences in the transit observation, questioning how this affects calculations.
  • One participant reiterates the desire for a method that does not require multiple observations, while expressing skepticism about the existence of such a method.

Areas of Agreement / Disagreement

Participants generally agree on the challenge of finding a method that does not involve multiple observations. However, there is disagreement regarding the feasibility of calculating 1 AU without using parallax, with some expressing doubt about alternative methods.

Contextual Notes

The discussion highlights the limitations of relying solely on a single observation and the potential complications introduced by angular measurements during the transit. There are unresolved questions about the specific calculations and assumptions involved in the proposed methods.

Who May Find This Useful

This discussion may be of interest to those studying astronomical measurements, historical methods of calculating distances in space, or the specific phenomena of Venus transits.

ExoP
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Hi!

I was wondering if anyone of you know how to calculate the astronomical unit 1 AU, using data from a Venus transit and not using the parallax method. I already have all the data from the 2012 transit; the time it was in phase 1 when it contacts the Sun's disk and when it leaves the disk in phase 4 etc. The latitudes are all included. I haven't found anything helpful yet. So, if you have any idea or maybe a website that explains how to calculate this without the parallax method, please help.

Cheers!
 
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This link has a clear elementary explanation of Halley's method proposed in 1716.

http://brightstartutors.com/blog/2012/the-transit-of-venus/

However this seems to be what you call the "parallax method" because it involves timing the same transit as seen from different locations on earth, essentially from different latitudes.

If you would like to help me understand what you are looking for (and help others in the same situation who might read the thread) you could be more explicit. Are you in fact looking for a method that does not involve making TWO separate observations of the same transit, from different latitudes on earth?
Are you looking for a method to find the AU from just your one observation?
I have a vague memory of having examined a calculation scheme of that type, but I'm not sure how it worked, someone else might know though.
 
Last edited:
That's right, I'm searching for a method that does not involve making TWO separate observations of the same transit.
 
How can you calculate is when there is an angle between the Venus transit, seen from us? Imagine the Sun, with Venus being a black dot. One of the dots are on the center of the Sun and the other slightly to the left in an angle under it. How should I consider this during my calculations? :S
 
Last edited:
ExoP said:
That's right, I'm searching for a method that does not involve making TWO separate observations of the same transit.

I don't think there's another way other than parallax.
 

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