Recently I upgraded my main astronomical software, from Guide 5.0 plus downloaded enhancements to Guide 6.0 (yes O Paul, I went and did it too). The main reason I upgraded was to gain some increased accuracy in planetary positioning. I have recently purchased equipment to do some astrophotography and my scope has had some problems with it’s tracking speed. It is very important that the positions of the objects I want to photograph are plotted accurately on the charts I use. Guide 6.0 accomplishes this by using the VSOP Theory to compute and plot the planet’s position to a theoretical accuracy of 0.01 arc sec. This is providing that you have entered your observing location as accurate as possible (within a couple of minutes).
While reading through the operation manual for Guide 6.0, I came across an interesting function under the Animation menu. Guide 6.0 gives you the option to lock onto an object and watch that object as it moves through the sky. This is a very useful option for those of you who like to see occultations, transits and eclipses. The operation manual mentioned that transits of Venus and Mercury across the face of the Sun were indeed things that could be computed and animated by Guide 6.0. The manual also mentioned that Venus would transit the Sun in 2004 and 2012 but did not provide a specific date. I guess the author wanted me to find those dates and times for myself. The author did say that these events are rare but he did not say anything about Mercurial transits So it was time to fire up the PC and do some investigating.
Well, the first thing I found out was that Mercury’s orbit and the orbit of the Earth are enough offset to each other that this type of phenomenon does not occur as often as I would have thought. In fact I had trouble finding a single incident until November 15th 1999 at 16:45 EST, and then only lust barely crossing the limb of the Sun. Now I was only looking for an instance that would be visible from Michigan. There was one other time that a transit happened in the 12 years that I ran my simulation for but it will not be visible from Michigan.
The transits of Venus are almost as rare. They will happen on June 8th 2004 at 07:00 EDT and then again on June 5th 2012 at 18:30 EDT. Both of these should be visible from Michigan providing there is an absence of clouds (which is almost as rare as these events). In order to witness any of these events you must have a telescope outfitted with a solar filter and an ocular yielding at least 50 power. NEVER LOOK AT THE SUN WITHOUT AN APPROVED SOLAR FILTER.
These events are wonderful ways to provide a visual demonstration of the differences in the sizes of the two bodies. I anticipate being around for all of these events and photographing them as their rarity makes them days to remember. Just a foot note to this article, while running through these animations on my computer I also simulated a partial solar eclipse on Christmas day in 2000 and a total lunar eclipse on January 21st 2000, both of which will be visible from Michigan. I will continue to look for more unusual events, like conjunctions, occultations, eclipses and transits. I will keep you posted.