HATOVAUM (Hydrogen-Alpha Transit of Venus Astronomical Unit Measurement)


(Hydrogen-Alpha Transit of Venus Astronomical Unit Measurement)

Re-calculating the Astronomical Unit using the upcoming Transit of Venus — IN A NEW WAY

I think I have an original idea — perhaps for the first time in my life.

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.(*)

The general question to be solved is, how far it is from the Earth to the Sun. That distance, the Astronomical Unit, was first historically measured during previous Transits of Venus (which are very, very rare). Sadly, neither the accuracy nor the precision of results of these earlier measurements were much to write home about — and those were the days when “writing home” meant entrusting your letter to a ship that may or may not make it to its destination without being attacked, destroyed in a storm, or just sunk to the bottom of the ocean for reasons unknown.BTW: every single seafaring/colonialist nation or empire of the last three centuries has sent its very best scientists to tackle this problem, starting in the 1760s.


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.

Having lots and lots of images means that we can beat down the errors to very low levels. How low, obviously, remains to be seen. Clearly some dry-run experiments involving some simultaneous images taken by as many observers as possible, spread over as many continents as possible, will be necessary.Again, this can be done strictly by amateur astrophotographers who have invested in their solar and astro equipment what an amateur or professional automobile mechanic might have in his/her tool set.Obviously I think this is a pretty cool project. But there’s not much time to get organized: the event is June 5/6, and it’s already May 9.Then again, I’m not asking these solar imagers to do anything they wouldn’t want to do already. I am sure that anybody who has an h-alpha scope is thinking very seriously about trying to take images of this event. After all, it won’t happen again in the lifetimes of anybody alive today. No one.

Exactly how the images should be made is up for discussion. I suspect that video recordings starting at each minute of viable observation, on the minute, stacked as each observer sees fit, and sent out in some sort of raw format (not compressed into a JPEG) will be advisable, but I am by no means any sort of an imaging expert. (Heck, I’m not even a duffer!)

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.

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