European Southern Observatory (ESO)European Association for Astronomy Education (EAAE) Observatoire de ParisInstitut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE)Astronomical Institute of the Academy of Sciences of the Czech Republic The Venus Transit 2004 European Science & Technology Week 2004Visit the websites of the VT-2004 organisers

The Venus Transit 2004

... the Observations

Goal of the observations

This page contains details about how to prepare and perform observations of the Venus Transit on June 8, 2004, in such a way that the results will be useful for the VT-2004 Observing Campaign. On the present page, you will find an overview of these observations, the details are described in the "Guidelines for Observers".

First of all, please note that in order to join the VT-2004 Observing Campaign, you will have to register with the programme. You will find details about how to do this on this page .

Basically, all observers should determine:

  • their geographical co-ordinates (longitude, latitude)

and attempt to make accurate timings of up to four specific moments during the transit:

  1. the moment when Venus' disc first "touches" the solar limb (the "first contact")
  2. the moment when Venus' disc has passed the solar limb and is "inside" the solar disc (the "second contact")
  3. the moment when Venus' disc first "touches" the other side of the solar limb (the "third contact")
  4. the moment when Venus' disc passes the solar limb (the "fourth/last contact")

You will find it useful to consult the Observing Guide and the Timing Hints' page before you attempt to perform these observations. Read also about how to deal with the "black drop" phenomenon.

It is important that you "use the correct time". Irrespective of your observing method and the local time in your region, you will have to deliver the times you determine in Universal Time ! It is therefore important that you familiarize yourself with the VT-2004 InfoSheet about "Universal Time" .

Moreover, whichever equipment and whichever observing method you use, we urge you to read the Safety Instructions!.

Preparations for the observations

The site and its geograhic coordinates

You should decide where you intend to do the observation on June 8, 2004 . From your backgarden? In (or near) which town? At a remote site?

Then you should determine the geographic longitude and latitude of your observing site. There are various ways of doing this, e.g.:

  • If you have access to a GPS (Global Positioning System) device, place yourself at the observing site and read the values indicated on the display. You may learn more about Navigation and GPS here.
  • Look at a local map on which geographic longitude and latitude are indicated. Try to measure to position of your observing site with a reasonable accuracy.
  • Consult the website to find the geographic longitude and latitude of the (nearest) town. This database is very large - it contains accurate positions of over 2 million towns, so the chances that you will find your place are quite good. Please note that you will have to register (with username and password) in order to access this site.

Note that for the longitude, "East" means east of the Greenwich meridian - most locations in Europe and Africa, and all in Asia and Australia therefore have eastern longitudes.

The equipment

Which equipment and observing method are you going to use? Will you project an image of the Sun on a screen? Will you use a camera? Is it already available or will you have to build (buy) it?

You will find an overview of various observing equipment at VT-2004 InfoSheet B2 . For most observers, and in particular those who are not very experienced amateur astronomers, the best observing method will be to project an image of the Sun from a small (binocular) telescope onto a white screen. Venus' disc may then be seen as a small black spot that slowly moves across the Sun's bright disc.

The observation method

You will find detailed instructions about how to perform the observations on the "Guidelines for Observers" page. They provide you with useful tips for good observing practice and outline the procedures that should followed in order to reduce measurement errors as much as possible.

So that you know when to be ready, predicted timings for the four contacts are available for a number of major cities in the world.

The Easy-to-Use Image Processing Facility

Within the VT-2004 programme, Basic Image Processing is available to everybody!

Digital images frequently contain more information than is obvious at first glance. We want to help you in getting the most out of your digital camera images. We have therefore created an easy-to-use facility at the Ondrejov Observatory (The Czech Republic) where you may submit your images and have a variety of well documented operations performed on them. The results are immediately displayed on your screen.

Delivery and use of the observations

When done, you should deliver your observations to the central VT-2004 computer; the details will be found on this page . Together with observations from many other participants in this wide programme, they will then be used to calculate the distance between the Earth and the Sun. More information about this will be done are available here .


Please direct any questions you may have in connection with the above information on observations to the organisers via email at