The 2012 Transit of Venus using HAM Radio

Bob Bruninga, WB4APR

Transit of Venus 2012: On June 5/6 2012 a rare Transit of Venus (7th human contact) will occur (Earlier ones were in 1639, 1761, 1769, 1874, 1882 and 2004) . The two occurences this centruy are the FIRST to ever occur since the discovery of Radio waves. This presents a unique opportunity to use radio at the speed of light to compare results from observations around the world in real time. In the 17th and 18th centuries, year long excurions to the corners of the globe by ship were necessary to make the necessary observations. Now in 2012, we can communicate this data from anywhere on Earth in under .05 seconds. Our goal is to compare the observations of amateur astronomers around the world using amateur radio. Using APRS group messaging and/or HF.

HAM Radio Calling Frequencies: HAMS are encouraged to go to any public area nearby where there will be obsrvers of the transit. Search for activities in your area. Then think of this as a mini-field-day opportunity to demonstrate Ham Radio by trying to contact other Transit observation sites. Here are some suggested calling frequencies. Choose the band appropriate for your time of day. See the world chart below to see who else is seeing the event in their mornings or evenings.

  • 40 meters - 7.180 MHz
  • 20 meters - 14.240 MHz
  • 17 meters - 18.140 MHz
  • 15 meters - 21.240 MHz
  • 12 meters - 24.940 MHz
  • 10 meters - 28.340 MHz

    VHF APRS: - On the local national APRS channel, send APRS message to CQSRVR with first two words being "CQ VENUS ..." followed by text. See the CQSRVR web page for details. Everyone who does this will see all other APRS Venus traffic too. But you can only send one message per 30 minutes.

    REPORT: Your report will be your City/Country name and the time of "second contact". Second contact is when Venus is first fully within the sun's disk. If anyone is still on the air 5 hours later, then also report "3rd contact" which is when Venus just touches the far side.

    IRLP, DSTAR and ECHOLINK: Feel free to also make VOIP contacts with anyone as well. Is there a special REFLECTOR that can be used for this event?

    The 2004 Transit: The Transit of Venus occurs in pairs once a century. Our last observation of this pair was on June 8th, 2004 at the Naval Academy on Farragut Field. Equipment used was a 10 inch meade reflector and camera obscura made from a 6 foot cube communication shelter with pin hole in door. Perfect skies. Photo at left shows Astronomy Professors Albert and Katz and former midshipman Hale (82) of comet Hale-Bopp fame. By the time of Sunrise on the East coast of the US, the transit was mostly complete with only the 3rd and 4th contact remaining as Venus exited the disk of the Sun. See our 2004 Report.

    CAMERA OBSCURA:In addition to the modern Meade Telescope we reproduced the technique used by 17th century observers to observe the sun. This consisted of a pin-hole in the side of a darkened room. In this case, we used a communications shelter with a small pin-hole in the door as shown below. You can clearly see Venus to the upper right left of the Sun's disk (inverted from reality):

    Observing the Parallax: The Transit of Venus is a fascinating event historically as it gave early astronomers the first mechanism with which to actually measure the distance from the Earth to the Sun and confirm their underestanding of the size of Venus. During the 6 hour or so event, there are 4 critical times as shown below. These instances will occur at slightly different times for observers at different Earth locations because of parallax. But generally begin at 0513z and end at 1126z.

    The parallax due to the separation of different observers will give enough differences in the observations to make meaningful measurements of the geometry of the event.

    Reporting your Observations: On APRS we will use the Global CQSRVR system which lets anyone anywhere share messages to everyone else that is logged into CQSRVR. To login, just send a message to CQSRVR with the first words of the message being CQ Venus ... Everyone else who is logged in will see your message. And from that point onward, you will get copies of any messages that others send. Since this is global, you are limited to only one message every 30 minutes. Here are the recommended messages:

  • On site . . . - Just login to CQSRVR to show you are on site and ready
  • 1st contact - Report your UTC time of first detection of Venus on the Sun's rim
  • 2nd contact - Report your UTC time when Venus is fully within the Sun's projection
  • 3rd contact - Report your UTC time when Venus just touches the far edge of the Sun
  • 4th contact - Report your UTC time of last sight of Venus

    Since the time between 2nd and 3rd contact is about 5 hours, you may send additional QSO messages every hour or so to maintain contact with other stations and share the excitement.

    2012 Naval Academy Team to Japan and Australia: Since this once-in-a-lifetime event will mostly only be visible in the Pacific area, the plan is to take teams from the US Naval Academy lead by Dr. Jim Huddle and Dr. Elise Albert to Australia and Japan where simultaneous observations in longitude can be made but at different latitudes.

    Some History: Many people don't realize that the mission of Captain Cook's 'round the world voyage in 1769 was to observe the transit of Venus in Tahiti.. (and secretly to lay clam to Antarctica if it existed)... Anyway, since it took him 3 years to complete his voyage, it took a while to collect these observations from other corners of the globe and then without computers or accurate global time, or any means of distance communications it took years for the data to be assemilated and analyzed.

    Radio and Wireless: Fortunately, for this 8th Transit of Venus, we can take advantage of another momentous discovery in Physics heralded by Marconi at the turn of the last century. His demonstration of the long distance communications capabilities of Radio waves in 1902 will add a new dimension to the Transit event by offering, for the first time in human history, the ability to witness the event simultaneously from excursions to the four corners of the world via the miracle of electronics communications. The map below shows the areas of the Earth where the Transit will be visible. In the USA, only the start of the Transit will be visible. Observers from China to Hawaii will have the potential to see the complete event.

    Communications: My participation in this event is to lead the worldwide Amateur Radio community into using the invention of radio to herald this event from all corners of the globe. We will use links via ionospheric propagation (HF) and satellite to share the event between the numerous excursions that will be taking place on that day throughout the world. Here are some of the ideas in work to develop support for this event:

  • HF Net: We will maintain communications via ionospheric propagation for check-in's from participating sites.
  • Digipeating via ISS: Participating observers will digipeat their observations
  • ISS Certificates: Some club could take charge of this special event and issue certificates
  • Expedition Tracking: Travels of expeditions will be tracked by GPS and relayed live to the APRS web page.
  • APRS Objects: Uplinked APRS objects will follow the ground track of the 4 contacts across the surface of the Earth.
  • Transit Tracking: And lastly we will use the coordinate tracking capabilities of the global APRS network to collect instantaneouse Venus position reports from other stations around the globe as shown below.

    If you are a HAM radio operator that will be involved in any scientific or public observations of this event, let us know so we can be watching the global APRS map for your team and your data if you will be posting APRS objects...

    Images of the Event: Although most images you will see of the anticiapted event will show straight line tracks and parallel paths for different observers at different longitudes, this is only after the images have been aligned with the plane of the Earths orbit. If observers orient their observations relative to local horizontal, instead of polar, then their image will not be aligned with others because of the different angle imposed by their 3D difference in longitude. And such tracks will not be straight lines either, because the Earth is rotating about 90 degrees during the 6 hour event. What we hope to plot in real time via APRS object reports are the actual (local horizontal) reports from different observers. THe results may appear as below...

    In order to get everyone to a consistent size, we need to work on a projection system that can project the Sun's image onto graph paper that is either 2.5" or 25 cm radius. The reason for the 2.5" or 25 cm projection size is because the size of APRS area circle objects are granular in size. This size yields a reasonable closefit to graph paper to yield a 500x500 grid. The following object in APRSdos plots a 2.5 minute radius yellow circle.


    To see how to do this in APRSdos, click here.

    Your challenge is to get the Sun's projection onto the graph paper to exactly that size, or conversly, to make your own GRID scaled to your own size projection so that it is evenly divided into +/- 2.50 minutes of LAT/LONG with enough grid lines so you can estimate position to the nearest 500'th the diameter of the Sun...

    There is a simple commercial product for projecting the sun. Its simply a hole in a box in which you put a small lens/telescope/(or half a binocular) and then bounce that off a mirror back into the box where the image is hidden from the bright sun. I like it's simplicity. See it

    This map is a LIVE FINDU.COM map of any reported sightings. Between now and 8 June you can practice your uplink and see if it shows up here: Now that this is on line, it was a poor choice becasue 00N/00W is a noman's land where null APRS posits some times go. Hence, you will see some unintended ICONS at the center 00/00:

    PASSES OF THE ISS DURING THE TRANSIT: The plot below shows all of the passes of ISS over HAM populated areas during the 6 hour event. It is recommended that a NET-CONTROL station take checkins on each bird (AO-27, and SO-50) and Packet be used on ISS to report from various opservation sites [NEEDS UPDATING TO 2012]...:

    THIS HAM RADIO PAGE is only a draft and should not be relied on for detailed astronomical data. For more Astronomical details on the Transit, see

  • Phone App
  • European Southern Observatory.
  • See times and world views)
  • see the Orpington Web page
  • Venus Project .
  • NASA's page.

    Bob Bruninga, WB4APR
    Senior Research Engineer
    US Naval Academy Satellite Earth Station

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