(Hydrogen-Alpha Transit of Venus Astronomical Unit Measurement)
Re-calculating the Astronomical Unit using the upcoming Transit of Venus — IN A NEW WAY
My proposal might allow us to measure, fairly accurately, one of life’s important questions: HOW BIG IS OUR UNIVERSE — using entirely equipment owned or built and operated by amateur astronomers.(*)
THIS IS NOT A TRIVIAL QUESTION.
The main difficulty is that the apparent parallax of Venus on the face of the sun was very small, even if your two observers were as far apart as possible. Plus, the Sun just appeared pretty much like a blank, featureless white or yellow disk with the occasional sunspot. Photographs were mostly used to help document contacts number 1 through 4. The famous “ink drop” problem made timing those contacts almost impossible, since different observers interpreted the phenomenon in different ways before. (Why did they get caught flat-footed like that? Simple: nobody had EVER done what they were doing before! The first time anyone tries something for the first time, there will be mistakes!)
My proposal is different. Forget about timing the contacts. Forget about the two parallel chords. None of that is necessary.
All we need is ten to twenty (or more) experienced solar imagers who know how to use a “hydrogen-alpha” filter (or dedicated solar telescope) to make sharp, crisp, in-focus and well-tuned images of the incredibly detailed surface of the Sun — at a large number of simultaneous events, for as long as they can. (The sun passing behind clouds, the computer runningout of disk space, the electricity cutting off, the sun going down, requirements for eating and household chorse, and so on are possible reasons for not continuing)
All these images must be time-stamped!!. Later on, all of these images from, hopefully, just about all over the world, get uploaded to some central repository. We take two images that were taken at the same instant from two observers, say, one in Australia, and one in British Columbia. We use some image processing software to align the two photos according to all of the easily visible h-alpha features on the surface of the sun — except for the two shadows of Venus. Those two shadows will block the view of slightly different locations on the face of the sun, which will be separated by roughly the diameter of Venus itself, if we calculated correctly, for those two locations. Then a few calculations give the angular parallax from this stereovision picture (’cause that’s what it really is!), and a few more calculations gives the distance from Earth to Venus, and then the diameters of the orbits of every single planet or comet or asteroid in our solar system, AND the sizes of the sun and everything around it, and so on and so on.
So, if you know anybody who owns a hydrogen alpha filter or dedicated telescope, please put them it touch with me, so we can get this project going ASAP, because time really is of the essence. We already have committed observers in the USA, Pakistan, and the UK, but that’s just a start.
(*) This measurement of the Astronomical Unit has been done before by scientists using a variety of methods. The best of them involved measuring parallaxes of asteroids and of Mars against either the Sun or the distant stars, as well as satellites and probes sent to the various planets. Most attempts using Venus were rather disappointing. I have not yet calculated how large the error bars will be in this proposed experiment, but I am hopeful that with lots of simultaneous images, we will be able to get those errors down to quite decent levels.