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Applets Venus Konjunktionen 1631 1639 1761 1769 1874 1882 2004 |
Transit Motion Applet
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Looking onto the ecliptic plane: The Earth and Venus are moving couterclockwise around the Sun. The orbital plane of Venus is inclined (by 3.39°) against the ecliptic plane. The grey part of Venus' orbit is below the ecliptic plane. At the point D (Descending Node) Venus is passing the ecliptic plane from north to south, and at A (Ascending Node) from south to north. This constellation (inferior conjunction and Venus passing a node) is a transit: Earth, Venus and Sun are in a straight line. |
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Looking parallel to the ecliptic plane from D to A. Venus is seen within the disc of the sun (transit). The actual inclination angle of Venus'
orbital plane is only 3.39°, and 7.00° for
Mercury. |
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Geocentric view looking to the Sun from the moving Earth. At inferior conjunction and passing a node Venus is seen within the disc of the Sun (transit). |
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The next figure traces the geocentric path of Venus starting from an inferior conjunction (transit) over a time interval of 4 years, ending by a superior conjunction (Venus is behind the Sun). There are 13 node passages of Venus: 
Choose The out most horizontal distance between the Sun and Venus is determined by the maximum elongation angle (46° neglecting the small orbit eccentricity of the Earth and Venus):  The maximum vertical angle may be up to 9.6° for Venus, and 6° for Mercury. To see a transit this angle must be smaller than 0,25° (radius of the Sun), i.e. Venus has to pass a node. 
The geocentric path of Venus starting from an inferior conjunction during a time interval of 8 years ends by another inferior conjunction (transit): 
The (sidereal) orbit period of Venus is TV=224.701 days, and TE=365.256 days for the Earth. The time interval T between two inferior conjunctions is:
After 8 years Venus will be back at the starting point with a difference of only 2.5 days: 5 x 583.92 d = 2,919.6 d The coincidence is better after a period of 243 years: 152 x 583.92 d = 88,755.8 d Four transits will happen within 243 years following a transit: 5 syn. per. + 76 syn. per. + 5 syn. per. + 66 syn. per. = 152 synodic periods
Use
Merkur- und
Venusdurchgänge - Grundlagen
und Geschichte (Antonius Schrode)
Transits of Venus (Peter M
Langford) Predictable
periodic and non-peridic events (Jan
Curtis) Transits of Venus and
Mercury, -1000 to +4000 Venus Passage: Cycles of
the Heart Der Transit innerer
Planeten über die Sonne
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