Pedro Castle, Friday 22nd June, 2012

The viewing of the Transit of Venus was, if you weren’t there, a huge success. Fortunately, we had seven telescopes for more than a thousand people to look through, and the atmosphere was orderly and convivial.

    Early risers can see Venus and Jupiter before and in the dawn, while Saturn, Mars and Mercury are visible when darkness falls.

      Saturn is close to the 15^th brightest star in the sky, Spica, which lies in the constellation of Virgo. Roughly halfway between this brilliant duo and the star Regulus in Leo, Mars glows distinctly in an area of dim stars. Mercury is visible as the sun sets, a good excuse to go the beach for the waning of the day.

    Further north from this line of the ecliptic, the bright star Arcturus is unmistakable. In the illustration above it is the alpha, α, orange star in the kilt of the Herdsman, Boötes.

    In ancient Babylon the stars of Boötes were known as SHU.PA. They were apparently depicted as the god Enlil, who was the leader of the Babylonian pantheon and special patron of farmers.

    Exactly whom Boötes is supposed to represent in Greek mythology is not clear. According to one version, he was a ploughman who drove the oxen in the constellation Ursa Major using his two dogs Chara and Asterion (from the constellation Canes Venatici). The oxen were tied to the polar axis and so the action of Boötes kept the heavens in constant rotation.

     The Boötes void, or the Great Void is a huge and approximately spherically shaped region of space, containing very few galaxies. It is located in the vicinity of the constellation Boötes, hence its name. At nearly 250 million light-years in diameter (approximately 0.27% of the diameter of the visible universe), the Boötes void is one of the largest known voids in the universe, and is referred to as a supervoid. According to astronomer Greg Aldering, the scale of the void is such that "If the Milky Way had been in the center of the Boötes void, we wouldn't have known there were other galaxies until the 1960s."

   The Boötes Dwarf Galaxy is a faint, satellite galaxy of the Milky Way located in Boötes about 197 000 light-years  away from Earth.

     To the naked eye, orange-yellow Arcturus has a visual magnitude of −0.04, making it the brightest star north of the celestial equator, and the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. However, Alpha Centauri is a bright binary star, whose unresolved components to the naked eye are both fainter than Arcturus. This makes Arcturus the third brightest individual star, just ahead of Alpha Centauri A (α Cen A), whose visual magnitude is −0.01.

     The apparent (visual) magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere. The brighter the object appears, the lower the value of its magnitude.

Transit Of Venus 5th June 5PM Camana Bay

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!