How You Can Learn a Lot from a Dot
Transit of Venus June 5th 2012
If you have heard of the recent Solar Eclipse visible from the Western USA, you may be interested to know that there is another trick the Sun is about to pull off on June 5th.
More importantly this event will be visible from the Cayman Islands, particularly at Sunset.
The planet Venus will appear as a “dot” which crosses the suns surface. The event, although not technically an eclipse, is called the Transit of Venus, (TOV).
Please also note this picture was taken with a small telescope fitted with a specialist filter.
Remember staring at the sun can cause serious damage to your eyesight.
So where and how can I see the event safely?
The Cayman Islands Astronomical Society, with the support of Dart Enterprises, will be holding a free rooftop event for the general public at 62 Forum Lane, Camana Bay. Directions on how to find us are available on a separate sheet.
From the rooftop terrace the event can be seen, in safety, using solar viewing glasses provided by Camana Bay, as well as through several telescopes belonging to the members of the Cayman Islands Astronomical Society (CIAS), all of which will be fitted with specialist solar filters.
There will also be a small exhibition and, hopefully, live pictures of the transit from other world-wide locations will be shown if the weather is cloudy. Representatives from other Astronomy Societies in the Caribbean will also be present. This event also marks the 21st anniversary of the Cayman Islands Astronomical Society.
Timing is fairly critical so we cannot use “Cayman-time” for this event, but generally speaking this will be a fairly relaxed affair. The “show” starts at 5:00PM and some important measurements will need to be made within the first half hour (see more information on this at the end of the article). Venus will then start a leisurely 6 hour transit across the Sun’s surface, although we will leave it somewhat earlier, as the sun sets, at around 7:00 PM.
If you are thinking of observing the Sun from elsewhere then I recommend waiting until close to sunset, so that sun is very low on the horizon and so safer to observe. We are all used to visitors taking photos of the setting sun but this time you will probably be staring at the sun for longer so take extra care.
Observing the Sun directly with a telescope or a camera with a telephoto lens will seriously damage your eyesight - and your camera might get damaged too.
You may also have heard that you can use welding glass to look at the Sun- this is true but the older type number 14 is the only safe grade. If you can see landscape through the glass as well as the sun, it is not good enough. Sunglasses? No way- unless they are the bone-fide solar-viewing glasses, which will be available on the rooftop terrace at Camana Bay.
So why is this an Important Event?
Quite simply Transits of Venus are among the rarest of predictable astronomical events. After a first attempt to predict the event, by Johannes Kepler, it was in fact observed 8 years later by Jeremiah Horrocks in 1639. This enabled, for the first time, accurate measurements in astronomical distances to be made, in particular the distance of the Sun from the Earth. This important “yard stick” is called the “The Astronomical Unit”. Each successive transit attracted world-wide expeditions including that of James Cook’s first voyage to Hawaii to see the event in 1769.
There is a curious mathematical pattern to the frequency of the transits. Think of a pair of transits 8 years apart, of which we are about to observe the second of the pair. Both of these transits occur in June. We then have to wait a mere 105 ½ years until the next pair. So the next pair of events will be in December 2117 and December 2125. Follow this by another long wait, but this time 121 ½ years, which brings us back to June but in 2247 and the cycle begins again.
Schools will be interested to know that there is a world–wide experiment to time the two points when Venus starts to cross the Sun’s disk. These two moments in time are not easy to measure; the second produces the famous “tear drop” effect.
The trick is to time exactly when the “drop” is inside the Sun’s disk. This time there is even a free “app” for your electronic gadgets, so you can practice the timing beforehand.
For more information visit http://www.transitofvenus.org/
Without doubt this is a very rare event and unique in our lifetime, and it is an interesting thought to think how old our children’s children will be in 2117 when the next transit occurs. So please just come with your eyes and enjoy!