Next live webcast: Total Lunar Eclipse of February 20-21, 2008

June 8, 2004

On Tuesday 8 June 2004 crossed the Sun's disk producing an extremely rare Venus transit. Venus could could be seen in silhouet as a large black spot. The transit was observed in its full extent throughout Asia, Europe, Iceland, Greenland and Africa. It was partially visible for observers in Australia, Japan, and the eastern states and countries of the Americas).

Astronet and several other institutions in The Netherlands and Belgium organized a live webcast of the Venus transit and acted as a node for online calculation of the Sun-Earth distance through the website Did you measure comtact timings? Please join our observations and enter your contact timings and geographical coordinates through our Observation Headquarters.

I shall try to show some of the results that are sent to Astronet soon. For the time being you might have a look already at the resulats that are shown at or the Venus Transit Photo Gallery of


Archive images by Paul Dolk at
Space Expo, Noordwijk, The Netherlands

Soon: archive images by
Mira Public Obervatory, Belgium

Between June 3 and June 13 Venus is
visible in SOHO's coronagraph


  • Theodore Lunar Observatory (Sydney)
  • CSIRO (Canberra)

  • Austria:
  • Österreichische Gesellschaft für Astronomie und Astrophysik (ÖGA2) (Innsbruck/Vienna)
  • Sonnenobservatorium Kanzelhoehe (Graz)
  • Universitäts-Sternwarte Wien (Vienna)

  • Belgium:
  • Mira Public Observatory (Grimbergen)
  • Université Libre de Bruxelles
  • Urania Public Observatory (Hove)
  • RUG-Volkssterrenwacht Armand Pien (Gent)

  • Brazil:
  • IP&D / FCC - Universidade do Vale do Paraíba - UNIVAP

  • (Peoples Republic of) China
  • Guangdong (China) Astronomical Society

  • Czech Republic:
  • Observatory and Planetarium Hradec Kralove
  • Express Astronomical Information (Karlovy Vary)
  • Express Astronomical Information (Brno)
  • Express Astronomical Information [Streaming video]

  • Denmark:
  • Dansk Rumforskningsinstitut (Copenhagen)
  • Astronomibladet

  • Egypt:
  • Expedicion Sonora VT-2004 Egipto (Cairo)

  • France:
  • Observatoire de l'Ecole Supérieure d’Optique (St. Etienne)
  • Observatoire Pic du Midi
  • Observatoire du Pic de Chateau Renards (Association "Astroqueyras",Hautes-Alpes)
  • Observatoire de Paris-Meudon
  • Observatoire de la Côte-d'Azur
  • Observatoire des Sciences de l'Univers de Besançon

  • Germany:
  • Astro-LiveCam Sternwarte (Hattingen)
  • Observationszentrum (NoRa)
  • Sternwarte Lohfeld (Bad Salzuflen)
  • Raumflugplanetarium "Juri Gagarin" (Cottbus)
  • Wendelstein-Observatorium (LMU München)
  • Sternwarte Peterberg
  • Astronomische Vereinigung Karlsruhe
  • VdS - Vereignigung der Sternfreunde
  • Kiepenheuer- Institut für Sonnenphysik (Freiburg)

  • Greece:
  • Exploratorium (Athens)

  • Hong Kong:
  • Hong Kong Astronomical Society

  • Hungary:
  • Polaris Observatory (Budapest)

  • India:
  • Vygyan Prasar
  • University of North Dakota V2K4 Expedition (New Delhi)
  • Nehru Planetarium (New Delhi)

  • Iran:
  • Kowsar-1 (K 1) Observatory (Isfahan)
  • Nojum, The Astronomy Magazine of Iran
  • Isfahan University, Physics Department
  • Adib Astronomy Society

  • Italy:
  • Istituto Nazionale di Astrofisica - INAF

  • Japan:
  • Yokohama Science Center, Astronomy Section
  • Nayoro Astronomical Observatory
  • Nagoya City Science Museum
  • Toyama Astronomical Observatory
  • Nishiharima Astoronomical Observatory
  • Kawabe Cosmic Park
  • Hoshinoko Yakata
  • Nakagawa Science Center
  • Nagasaki Science Museum

  • Macao:
  • Macao Astronomical Society

  • The Netherlands:
  • Sander Klieverik at Denekamp
  • Sterrenkids Webcam

  • New Zealand:
  • National Maritime Museum (Auckland)
  • One Tree Hill Domain

  • Norway:
  • (Oslo)

  • Poland:
  • Astronomical Institute of Wroclaw University (in H-alpha line)
  • Center of Theoretical Physics, Polish Academy of Sciences (Warszaw)
  • Center of Theoretical Physics, Polish Academy of Sciences (Warszaw)
  • Lodz Planetarium
  • Institut of Physics of Szczecin University
  • Polish Amateur Astronomy Association - Section of Solar Observations

  • Portugal:
  • COAA Centro de Observacao Astronomica no Algarve Poio (Portimão)
  • Centro Multimeios Espinho - Centro de Astrofisica da Universidade do Porto

  • Reunion:
  • Astroamateur Jacky FRANCOISE
  • Observatoire astronomique des MAKES

  • Romania
  • Astronomical Institute of the Romanian Academy (Bucharest)

  • Slovakia:
  • Slovak Union of Amateur Astronomers - Public Observatory Rimavska Sobota

  • Spain:
  • Parque de las Ciencias de Granada
  • Instituto de Astrofísica de Andalucía
  • Agrupación Astronómica de Málaga SIRIO
  • Solar Observation Network NSO/GONG - with images from Observatorio del Teide, Izaña - Tenerife (IAC)
  • SAROS Live (Gran Canaria, Canary Islands)
  • Agrupación Astronómica Isla de la Palma
  • Retransmission together with the Instituto Astrofísico de Canarias (IAC)
  • Universitat de Barcelona
  • Agrupació Astronómica Vizcaína - Bizkaiko Astronomi Elkartea y el I.E.S. J.M. Barandiaran de Leioa
  • Observatorio UCM - Depto. Astrofísica - ASAAF (Madrid)
  • Saros Group - Scientific Expeditions (Canary Islands)
  • Saros Group - Scientific Expeditions (Canary Islands)
  • Agrupación Astronómica de Sabadell (Barcelona)
  • Instituto de Astrofisica de Andalucia (Granada)

  • Sri Lanka
  • Arthur C. Clarke Institute (ACCIMT) (Katubedda, Moratuwa)

  • South Africa:
  • Pretoria Centre of the Astronomical Society of Southern Africa
  • Braam van Zyl, at Boyden Observatory, Bloemfontein
  • South African Astronomical Observatory

  • Sweden:
  • Images from the Swedish 1-m Solar Telescope (SST) in La Palma (Canary Islands)

  • Switzerland:
  • Olivier Staiger
  • Astronomischer Verein Antares

  • United Kingdom:
  • Worthill Observatory
  • Armagh Observatory
  • East Antrim Astronomical Society (EAAS) (Ballymena)
  • University of Central Lancashire
  • Neatherd High School

  • USA:
  • Sun-Earth Day: Views with Observatories
  • Fort Worth Museum
  • Kidz On-Line
  • University of North Dakota (UND)

  • Yugoslavia (Serbia and Montenegro):
  • Astronomy Club "Milutin Milankovic" (Zrejanin)
  • Mathematical Dept. of Faculty of Science and Mathematics


  • Hot Shots from SOHO
  • The very latest SOHO images (ESA)
  • The very latest SOHO images (NASA)
  • Passage de Vénus devant le Soleil: observations en temps réel par le télescope EIT/SOHO

  • TRACE:
  • Venus Transit 8 June 2004


    Transits of Venus across the disk of the Sun are among the rarest of planetary alignments. Only six such events have occurred since the invention of the telescope (1631, 1639, 1761, 1769, 1874 and 1882). The next two transits of Venus will occur on 2004 June 08 and 2012 June 06.

    Venus takes more than six hours to track across the Sun. Times shown are Universal Time. Greatest transit is the instant Venus passes closest to the Sun's center. Astronomy magazine illustration by Roen Kelly.

    The principal events occurring during a transit are characterized by contacts. The event begins with contact I which is the instant when the planet's disk is externally tangent with the Sun. The entire disk of the Venus is first seen at contact II when the planet is internally tangent with the Sun. During the next several hours, Venus gradually traverses the solar disk at a relative angular rate of approximately 4 arc-min/hr. At contact III, the planet reaches the opposite limb and is once again internally tangent with the Sun. The transit ends at contact IV when the planet's limb is externally tangent to the Sun. Contacts I and II define the phase called ingress while contacts III and IV are known as egress. Greatest transit is the instant of minimum angular separation between Venus and the Sun as seen from Earth's geocenter.

    Courtesy: Fred Espenak

    The entire transit (all four contacts) is visible from Europe, Africa (except western parts), Middle East, and most of Asia (except eastern parts).

    Courtesy: ESO

    The Sun sets while the transit is still in progress from Australia, Indonesia, Japan, Philippines, Korea, easternmost China and Southeast Asia. Similarly, the Sun rises with the transit already in progress for observers in western Africa, eastern North America, the Caribbean and most of South America. None of the transit will be visible from southern Chile or Argentina, western North America, Hawaii or New Zealand.

    This is one frame of an animation that shows both the track of Venus across the Sun and the regions on Earth where the transit will be visible. Contact times and the exact path Venus will take across the Sun differ slightly for observers in different locations. The path and times shown here are correct for an observer located at Earth's center, but contact times will not differ from these by more than 7 minutes anywhere in which the contacts are visible. The Earth image is centered on the geographical location where Venus lies directly overhead.
    Click for the Astronomy magazine animation (AVI, 1,3 Mb) by Francis Reddy.


    The apparent semi-diameters of Venus and the Sun are 29 arc-seconds and 945 arc-seconds respectively. This 1:32.6 diameter ratio results in an effective 0.001 magnitude drop in the Sun's integrated magnitude due to the transit. This simply means that the Sun will be as dangerous for our eyesight at the time of the Venus Transit as it is on any normal day, when there is no planet in front of the solar disc.


    The use of #14 shade welding glass or eclipse shades will permit a large number of people who do not have specialized equipment to observe this event. However, as the planet approaches the limb of the sun, subtleties like the black drop effect may not be discernible.Pinhole projectors are a safe, indirect viewing technique for observing an image of the sun. While popular for viewing solar eclipses, pinhole projectors suffer from the same shortcomings as unmagnified views when Venus approaches the edges of the sun. Small features like the black drop effect and the halo around Venus while it straddles the solar edge may not be discernible.

    Courtesy: European Southern Observatory

    You may project a magnified view of the sun through a telescope onto a surface, but the technique often has its own limitations. For example, large reflector telescopes can generate too much heat by concentrating a lot of the sun's energy on the secondary mirror and eyepiece. Likewise, Schmidt-Cassegrain telescopes can experience too much heat build-up as the light bounces internally. Also, magnified projections usually have an exposed focal point beyond the eyepiece where bystanders could inadvertently burn themselves. Constant attention is required.

    The transit of Venus is perhaps best viewed directly when magnified, which demands an appropriate solar filter over the large end of the telescope. Do not use small filters that fit over the eyepiece, for the concentrated sunlight can shatter them. The sun's energy must be attenuated before it enters the telescope. A filtered, magnified view will show the planet Venus, the "black drop" effect, and sunspots.

    No matter what technique you use for viewing the sun, do not stare continuously at the sun! Always give your eyes a break.


    In earlier times, astronomers used transits of Mercury and Venus to get information about the dimensions of the solar system: the size of the Sun, the distance of Venus, and the distance between us and the Sun, which is called the astronomical unit (AU). To fix that important quantity, astronomers used the method of triangulation.

    The first astronomer to recognize the importance of observing transits of Mercury and Venus was Edmund Halley (1656-1742). It appeared to the observer, using a telescope as the lens of a camera obscura (never look directly at the Sun through a telescope!) as a black dot crossing the surface of the Sun. The first astronomers to use telescopes to observe the transit of Venus were Jeremiah Horrocks (1618-41) and William Crabtree (1610-44) in 1639.

    Astronomers travelled to remote parts of the world to observe the transits of Venus in 1761 and 1769. To observe the transit of 1769, Captain Cook sailed from England to Tahiti. He discovered Hawaii and a few other places as bonuses along the way; it is not often that the side benefits of astronomical research are so apparent.

    How accurate were the measurements of Cook? The "dusky shade round the body of the Planet" as he descrtibed the appearance of Venus was a problem. Intense sunlight filtering through Venus' atmosphere fuzzed the edge of the disk and decreased the precision with which Cook could time the transit. For this reason, his measurements disagreed with those of ship's astronomer Charles Green, who observed the transit beside Cook, by as much as 42 seconds.

    Cook's observations

    Cook and Green also observed the "black drop effect." When Venus is near the limb of the sun--the critical moment for transit timing--the black of space beyond the Sun's limb seems to reach in and touch the planet. You can recreate the black drop effect with your thumb and index finger: Hold the two in front of one eye and narrow the distance between them. Just before they touch, a shadowy bridge will spring across the gap. According to John Westfall, writing for Sky & Telescope magazine in June 2004, "this is simply the result of how two fuzzy bright-to-dark gradients add together." The black drop effect, like the fuzziness of Venus' atmosphere, made it hard to say just when the transit began or ended.

    Black drop effect

    This was a problem for observers elsewhere, too, not only Cook in Tahiti. In fact, when all was said and done, observations of Venus' 1769 transit from 76 points around the globe, including Cook's, were not precise enough to set the scale of the solar system. Astronomers didn't manage that until the 19th century when they used photography to record the next pair of transits. And even then an incertainty in the measurements remained.

    In recent years, radio signals emitted by spacecraft as they pass behind Venus have enabled us to obtain very accurate planetary positions and masses, as well as the distance between the Earth and the Sun. Because of these results from space exploration, observing this and future planetary transits will be of less scientific importance, but they will of course continue to be great public and educational interest.

    What else is there to be seen? Look before and during ingress and during and after egress for a spectacular 'light ring' around the black silhoutte of Venus. This is caused bu sunlight that is refracted by Venus' thick atmosphere. It was after observing this light ring in 1761 that Russian astronomer Mikhail Lomonósov realized that Venus is surrounded by an atmosphere.

    The light ring in 1874

    Carl Koppeschaar


    General information:

  • Fred Espenak, NASA's GSFC: 2004 and 2012 Transits of Venus
  • ESO: The Venus Transit 2004
  • Prof.Dr. Udo Backhaus: Observing, Photographing and Evaluating the Transit of Venus, June 8th, 2004
  • Steven van Roode: Transit of Venus, 8 June 2004
  • The Transit of Venus: North American Viewer's Guide
  • Orpington Astronomical Society: Transit of venus 2004
  • Transit of Venus, June 8, 2004
  • David Sellers: The Transit of Venus & The Quest for the Solar Parallax
  • Transit of Venus June 8, 2004
  • Astronomy Picture of the Day: Phases of Venus

    History of Venus Transits:

  • Smithsonian Institution libraries: Chasing Venus, Observing the Transits of Venus, 1631-2004
  • James Cook and the Transit of Venus
  • The 1882 Transit of Venus: Observations from Wellington, South Africa.
  • Jeremiah Horrox: Venus in sole visa
  • The First Observations of Transits
  • Historical Observations and Global Expeditions
  • Historical Observations of Venus Transits in Iran

  • The Black Drop Effect

  • The "Black Drop" Effect

    Maps and plots of the Venus Transit:

  • Daniel Falla and John Brooks: June 8th Venus Transit

    Topocentric contact times and corresponding altitudes of the Sun:

  • Circumstances for Cities (International)
  • Circumstances for Cities (USA)

    Past and future Venus Transits:

  • Project Pluto: Transits of Venus and Mercury, -1000 to +4000


  • Eclipse Home page: Eye Safety And Solar Eclipses
  • Safety!
  • Sky & Telescope: How to observe the Sun safely

    Database with geographical coordinates:

  • Heavens Above: Select Country

    Time synchronization:

  • UTC Time Zone (accurate within 0.4 seconds)
  • Chronograph Atomic Time Clock

    Solar Parallax Calculation:

  • Observation Headquarters
  • Steven van Roode: The solar parallax and the distance of the sun

  • Weather:

  • Meteosat Images from the University of Ulm
  • (USA)
  • Commonwealth Bureau of Meteorology: Current Australian Region Satellite Images

    Previous webcasts organized by Astronet:

  • Total lunar eclipse 4/5 May 2004
  • Total lunar eclipse 8/9 november 2003
  • Annular solar eclipse, May 31, 2003
  • Total lunar eclipse, May 15-16, 2003
  • Mercury transit, May 7, 2003