How to See ?Much of the world can witness the 2012 transit of Venus. The date depends on what side of the International Dateline you will be observing.
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Past and future transits |
HistoryKnow how the ancient Greek, Egyptian, and Chinese observers observes the transit.
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Sky Watchers' Association of North Bengal (SWAN)
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Know About The Rare Alignment Of Venus Transit |
Planet Venus |
Conjunctions
Diagram of transits of Venus and the angle between the orbital planes of Venus and Earth
Venus, with an orbit inclined by 3.4° relative to the Earth's, usually appears to pass under or over the Sun in the sky at inferior conjunction.A transit occurs when Venus reaches conjunction with the Sun at or near one of its nodes, the longitude where Venus passes through the Earth's orbital plane, called the ecliptic. Although the inclination between these two orbital planes is only 3.4°, Venus can be as far as 9.6° from the Sun when viewed from the Earth at inferior conjunction.Since the angular diameter of the Sun is about half a degree, Venus may appear to pass above or below the Sun by more than 18 solar diameters during an ordinary conjunction.
The Pattern of Transit
The transit occur in a pattern that repeat every 243 yers,the pattern is 105.5, 8, 121.5, 8 years and this patern will continue until 2846, when it will be replaced by a pattern of 105.5, 129.5 and 8 years.So, the 243-year cycle is relatively stable, but the number of transits and their timing within the cycle will vary over time.
The Pattern of Transit
The transit occur in a pattern that repeat every 243 yers,the pattern is 105.5, 8, 121.5, 8 years and this patern will continue until 2846, when it will be replaced by a pattern of 105.5, 129.5 and 8 years.So, the 243-year cycle is relatively stable, but the number of transits and their timing within the cycle will vary over time.
Observations
Measuring Venus transit times to determine solar parallax
The original scientific interest in observing a transit of Venus was to determine the size of the solar system by employing the parallax method and Kepler's third law. The technique involved making precise observations of the slight difference in the time of either the start or the end of the transit from widely separated points on the Earth's surface. The distance between the points on the Earth was then used as a baseline to calculate the distance to Venus and the Sun via triangulation.
Johannes Kepler became the first person to predict a transit of Venus, by predicting the 1631 event in 1627.But his methods were not sufficiently accurate to predict that the transit would not be visible in most of Europe,so nobody was able to make arrangements to observe the phenomenon.
Johannes Kepler became the first person to predict a transit of Venus, by predicting the 1631 event in 1627.But his methods were not sufficiently accurate to predict that the transit would not be visible in most of Europe,so nobody was able to make arrangements to observe the phenomenon.
Black drop effect
Fig: SWAN's Image of Black drop effect. ToV 2004. Pic. Debasis Sarkar . Nikon FE II.
The black drop effect is an optical phenomenon visible during a transit of Venus.
After second contact, and again just before third contact during the transit, a small black "teardrop" appears to connect Venus' disk to the limb of the Sun.
The black drop effect was long thought to be due to Venus' thick atmosphere, and indeed it was held to be the first real evidence that Venus had an atmosphere. However, it is now thought by many to be an optical effect caused by the smearing of the image of Venus by turbulence in the Earth's atmosphere or imperfections in the viewing apparatus. With precise measurements, however, a black drop effect was observed from outside the Earth's atmosphere during the 1999 and 2003 transits of Mercury, although Mercury has no significant atmosphere.
In the June 8, 2004 transit of Venus, many observers reported that they did not see the black drop effect, or at least that it was much less pronounced than had been reported in earlier centuries' transits. Larger telescopes and better optics may have been a factor.
After second contact, and again just before third contact during the transit, a small black "teardrop" appears to connect Venus' disk to the limb of the Sun.
The black drop effect was long thought to be due to Venus' thick atmosphere, and indeed it was held to be the first real evidence that Venus had an atmosphere. However, it is now thought by many to be an optical effect caused by the smearing of the image of Venus by turbulence in the Earth's atmosphere or imperfections in the viewing apparatus. With precise measurements, however, a black drop effect was observed from outside the Earth's atmosphere during the 1999 and 2003 transits of Mercury, although Mercury has no significant atmosphere.
In the June 8, 2004 transit of Venus, many observers reported that they did not see the black drop effect, or at least that it was much less pronounced than had been reported in earlier centuries' transits. Larger telescopes and better optics may have been a factor.