The Planetary Transit Special Award (Venus Transit)

Planetary Transit Special Award Coordinator:

Aaron B. Clevenson
19411 Cluster Oaks Drive
Humble, TX 77346-2918
(281) 852-4667

Venus Transit 2012 Award Pin

Submissions must have been received before the end of 2012. This deadline has passed. No additional submissions will be accepted.


Welcome to the Astronomical League's Planetary Transit Special Award site.  The purpose of this award is to provide an opportunity to relive the excitement of being on a planetary transit expedition and to derive a value for the Astronomical Unit, and to recognize those who participate.  This award is being presented in collaboration with NASA.

Planetary Transits are rare events.  They occur when a planet (Mercury or Venus) passes in front of the sun as seen from Earth.  This requires the the inner planet be at inferior conjunction along the line formed by the intersection of the Earth’s orbital plane and the planet’s orbital plane (the line of nodes).  Only when these two conditions are met will a transit occur.

Although materials for this program are still being developed, some of the details are known.  We will update this site as we get closer to the event and have more details finalized.

*** Safety Warning ***

Observing the Sun can be dangerous if not done correctly.  Never look at the sun directly.  Even when it is low on the horizon and doesn’t appear to be dangerously bright, it is hazardous.  When the sunlight passes through a lot of atmosphere, as it does when it is near the horizon, the blue light is scattered, so less overall light reaches you.  But the red and infrared light passes through relatively undimmed and can harm your eyes.  So do NOT ever look at the sun.  Use one of the safe techniques mentioned below.

Information on the Next Planetary Transit: Venus:

This web page and the special award will only be available when there is an upcoming transit.

The next planet to transit the sun is the planet Venus on June 5/6, 2012.  Details on this transit are available from NASA on this site:

Note that for most of us in the United States, the transit will end after sunset, so we will not be able to observe the entire event. Timings for the contacts are:

               Event                                   UT

               Contact I                               22:09:38, June 5

               Contact II                              22:27:34, June 5

               Maximum Transit                  01:29:36, June 6

               Contact III                             04:31:39, June 6

               Contact IV                             04:49:35, June 6

Definition of contact points:

  • Contact I:  when the leading edge of the planet first touches the edge of the Sun.
  • Contact II:  when the planet is initially completely on the disk of the Sun.
  • Maximum Transit:  when the planet is at maximum transit (the middle).
  • Contact III:  when the leading edge of the planet first reaches the far edge of the Sun.
  • Contact IV:  when the planet is initially completely off the disk of the Sun.

Venus is so close to the Earth that its silhouette is visible without magnification, but be sure to use proper eye protection to protect your eyes.

(The next transit after that is the planet Mercury on May 9, 2016.  Mark your calendar.)

How to Safely Observe the Transit:

Observing the Sun can be very dangerous.  Be very careful.  Never look at the Sun without proper filters.  A safe filter must filter 99.999% of the sunlight at visible as well as invisible wavelengths (infrared and ultraviolet).  Damage can be immediate and permanent!

Option 1: Pinhole projection.  This is a great, low-tech way to watch the event.  It lets multiple people see it at the same time.  Do NOT look through the hole at the Sun.  Put a small pinhole in the center of a card.  Let the light coming through the hole hit a large white card or piece of paper about 3 feet away.

Option 2: Eyepiece projection.  This technique will work for a small telescope or a pair of binoculars mounted on a tripod.  Do NOT look through the binoculars or the telescope when it is pointed near the sun!  Do NOT do this with a large telescope, the optics may overheat and be permanently damaged.  If you are using binoculars, cover one of the objective lenses.  Point the equipment at the Sun.  Then hold up a white card or piece of paper so that the light coming out of the eyepiece is projected onto the paper.

Option 3: Solar Sunglasses.  These sunglasses are easily available on the internet and will be available in local stores as the time draws near.  Once you have them, check to be sure that there is no damage.  Put them on, and look at a bright incandescent light bulb. You should be able to see the glowing filament. Make sure that there are no cracks, creases, or pinholes. Even a small pinhole will let in a potentially dangerous amount of light from the Sun.  It you see any damage at all, do NOT use them. Also note that there are NO sunglasses that are safe for looking at the sun.

Option 4: Binoculars or a telescope with a solar filter. They should have a filter at the front end of them. Do NOT use solar filters that attach at the eyepiece end. Make sure that there is no damage on the filter before you use it.  Be sure to cover the finder scope.

Option 5: A solar telescope. These are telescopes specifically designed for observing the sun usually at specific wavelengths  (e.g. H-alpha – 656.3 nm, Calcium K – 393.4nm). I believe that the view in a standard telescope with a standard solar filter will be more pleasing.

Option 6: Shade #14 welder’s glass.  It is critical that you use shade #14 or higher. The higher number the more filtering.  If you are unable to get the shade #14 welder’s glass, then we recommend that you use one of the projection methods (options 1 or 2 above). If you combine more than one piece, your total must be higher than 14.  Two pieces should total 15. Three should total 16.  If you use more than one piece, tape them together so that you will always be sure to be looking through all of the filtering. A higher number is always better.

Historical Information:

Pierre Gassendi, a French astronomer, is credited as being the first person to witness a transit of Mercury in 1631.  He tried to observe the transit of Venus a month later, but it was not visible in Europe.  Jeremiah Horrocks and William Crabtree, British astronomers, observed the next transit of Venus on December 4, 1639.

In 1677, Edmond Halley observed a transit of Mercury from Saint Helena's Island. He realized that the careful timing of transits could be used to determine the distance of Earth from the Sun. His technique relied on observations made from distant locations through measuring parallax.  (Parallax is the angular shift in the location of a nearer object against a distant background due to a change in observing location.)  Taking this measurement would enable astronomers to calculate the value of the Astronomical Unit (Earth’s distance from the Sun) and in turn calculate the distances to all of the planets. Venus transits provide a more accurate parallax measurement than Mercury transits because Venus is closer to the Earth resulting in a larger parallax.

Expeditions to observe the transits in 1761 and 1769 did not yield useful results.  Another set of observations of Venus were done in 1874 and 1882. Once again, the results were not of high quality.  One problem plaguing these expeditions is an effect called the "black drop".  The edge of the planet's disk appears to deform and cling to the limb of the Sun.  The "black drop" is the result of seeing problems due to the Earth's turbulent atmosphere.

Rules and Regulations:

There will be a general certificate available for download by anyone hosting a transit viewing.  The host can then provide these certificates to those who participate as a memento of their experience and to commemorate this very rare experience.

There will also be a special award for those who undertake the process to calculate the value of an Astronomical Unit.  The special award will include a certificate and a pin.

To receive this special award from the Astronomical League, you must meet these requirements:

  • Be a member of the Astronomical League.
  • Observe as much of the transit as is visible from your location.
  • Sketch the event as you see it, noting the timings for the contact points.
  • Include your Latitude and Longitude of observation.
  • Calculate the value of the Astronomical Unit.  Instructions on how to do this are available on the NASA website.
  • Submit your work per instructions that will appear here by the end of the year.

There are three techniques on the NASA website to calculate the value of the AU. We encourage you to try all three. Only one is required for the special award.  This information is available on this NASA Website.

To receive this special award from the Astronomical League (certificate and pin), you should follow the instructions on the NASA website for the Level 2 certification.  Once you have completed one of the AU calculations, make a screen print of your entries or write down the information (you can also use Copy/Paste to get a copy), you will then be able to print out your certificate.  Please send an email to the AL Planetary Transit Special Award Coordinator, Aaron Clevenson, at  Include the screen print or data you entered on the NASA Website  including the results for the calculation of the AU.

Please include this information:

  • Your name
  • The name of your astronomy club or Member-At-Large
  • Your address
  • The Name and address of your awards coordinator if we should send it to them for presentation
  • Were you able to actually see the transit yourself?  And if not, why not?

The certificate for anyone viewing the Venus Transit is available here or on the NASA website.

Planetary Transit Special Award Coordinator:

Aaron B. Clevenson
19411 Cluster Oaks Drive
Humble, TX 77346-2918
(281) 852-4667

Related Links:

Printable Version of this Page
PDF File Format

Planetary Transit Special Award Links

NASA information on Transits:
Sun Earth Day Website:

The main page at NASA for this Venus Transit is:
The page describing the certifications is: