Witness a transit of Venus! This section guides observers to observe the 2012 Transit of Venus safely. Feature topics include:
- Where to Be (and When)
- Safe Viewing Techniques
- Travel and Tours
- Planning Community Transit of Venus Events
Where to Be (and When)
Whether and when you can see the 2012 transit of Venus depends on your location. Key highlights include the four "contacts" near the beginning and end of the transit when Venus appears to touch the edge of the sun. Most of North America sees the beginning of the transit in the afternoon and evening (find a clear western horizon!) on June 5, whereas much of Eurasia sees the end of the transit in the morning (find a clear eastern horizon!) on June 6.
Click to access and enlarge PDF version of map showing visibility of 2012 transit of Venus. Courtesy of Fred Espenak (NASA GSFC), who provides additional transit of Venus data from NASA.
To see an animation of how the sun appears at Region X, near Iceland, see http://youtu.be/3b7a_zXMnnU.
Time is of the Essence
The diagram (click for enlarged PDF version) shows the path of Venus across the sun and the contact times from an earth-centered perspective. However, from different locations on earth, the exact contact times vary by minutes or seconds. That slight difference in times is the essence of a transit's value, for it allowed astronomers to calculate the size of the solar system. The entire event takes about 6 hours 40 minutes. The times in the diagram are in Universal Time, or essentially Greenwich Time. For simplicity, visit http://www.transitofvenus.nl/details.html, or select a nearby city from one of the Links: Where to Be.
So, is the transit of Venus visible June 5 or June 6?
It depends on your time zone. Generally, for the Americas where it is visible (blue colors on map below) the 2012 transit occurs the evening of Tuesday, June 5, 2012. For Eurasia and Africa where it is visible (sage colors on map), the latter part of the transit is seen the morning of June 6, 2012. Map courtesy of Steven van Roode.
[Note: Some confusion may arise from published tables with a title stating the 2012 transit of Venus is on June 6. By default, these tables are titled by the mid-transit point in Universal Time. Because the middle of the transit occurs just after midnight on June 6 in Greenwich Time (even though it's not visible then in Greenwich), the title nonetheless affirms June 6. ]
Spanish Version of Sun Funnel: El Embudo Solar
A Spanish version of the instructions for building a Sun Funnel now accompany the English version. Thanks go to Manuel Alvarez of Instituto de Astronomia Sede Ensenada B.C. for translating the original text. Alvarez writes, "We are planning to observe the Transit of Venus at the same place that Joaquín Velásquez de León and Abad Chappe d'Auteroche observed the transit on June 3rd. 1769; (243 years ago); (i.e. "Visita de Santa Ana", near La Paz in Baja California Sur (Velasquez) and "Misión de San José del Cabo", Baja California Sur), (Chappe). At the same time, we are considering building some Sun-Funnels for people to observe the Sun and the Transit."
Build a Sun Funnel for Group Viewing with a Telescope
One of the best ways for a group of people to view the magnified sun safely is to use a rear screen projection that is enclosed. Because no one is exposed to the intense light path, a Sun Funnel allows a crowd of people to see concurrently the transit of Venus, sunspots, or eclipses. After leading a hands-on workshop to make the inexpensive devices, AAS Press Officer Richard Tresch Fienberg wrote and illustrated Build a Sun Funnel for Group Viewing of Sunspots and the Transit of Venus. The how-to manual gives clear, step-by-step assembly instructions and sources for inexpensive materials.
Another hands-on workshop to build Sun Funnels will be at the Great Lakes Planetarium Association (GLPA) 2011 Annual Conference in Champaign, IL, on October 20, 2011. Several GLPA members successfully used a Sun Funnel to witness the 2004 transit of Venus.
See Eye Safety for more techniques and advice for viewing the sun safely.
SPANISH VERSION; courtesy of Manuel Alvarez, Instituto de Astronomia Sede Ensenada B.C.
Links: Where to Be
http://transitofvenus.nl/wp/where-when/local-transit-times/Excellent site automatically calculates your local circumstances (time of sunrise, time of sunset, times of all four contacts, altitude of the sun, etc.), based on your Internet connection. You can easily modify your location with a provided Google map. From Steven van Roode.
http://www.transitofvenus.nl/transit_venus_2012_ingress.jpg
World map of ingress times (contacts 1 & 2).
http://www.transitofvenus.nl/transit_venus_2012_egress.jpg
World map of egress times (contacts 3 & 4).
http://sunearthday.nasa.gov/2012/about/event_locations.php
Interactive map shows NASA Sun-Earth Day Event Locations, keeping you up to date on what's happening in your neighborhood. Upload your own events here, too.
http://www.transitofvenus.org/trove
TROVE: Celebrating the Riches of the TRansit Of VEnus. The Michiana area near the Michigan-Indiana, USA, border is a hub of activity related to the transit of Venus. Join us to celebrate the math, science, and art of this celestial phenomenon.
http://eclipse.gsfc.nasa.gov/transit/venus0412.html:
"The global visibility of the 2012 transit is illustrated with the world map... The entire transit (all four contacts) is visible from northwestern North America, Hawaii, the western Pacific, northern Asia, Japan, Korea, eastern China, Philippines, eastern Australia, and New Zealand. The Sun sets while the transit is still in progress from most of North America, the Caribbean, and northwest South America. Similarly, the transit is already in progress at sunrise for observers in central Asia, the Middle East, Europe, and eastern Africa. No portion of the transit will be visible from Portugal or southern Spain, western Africa, and the southeastern 2/3 of South America." Courtesy of Fred Espenak.
http://sunearth.gsfc.nasa.gov/eclipse/transit/venus/city12-1.html
Contact times (Universal Time) and corresponding altitudes of the Sun for 121 international cities. From Fred Espenak.
http://sunearth.gsfc.nasa.gov/eclipse/transit/venus/city12-2.html
Contact times (Universal Time) and corresponding altitudes of the Sun for 60 cities in the USA. To convert to Daylight Saving Time, subtract 4 hours if you are in Eastern Time Zone; subtract 5 hours in Central Time Zone; subtract 6 hours in Mountain Time Zone; subtract 7 hours in Pacific Time Zone. From Fred Espenak.
http://eclipse-maps.com/Eclipse-Maps/Transits_files/ToV2012map_1.jpg
Global map by Michael Zeiler depicts the zones of visibility for the 2012 transit of Venus.
http://www.usno.navy.mil/USNO/astronomical-applications/data-services/upcom-transits/?sear
World map of visibility; General description, geocentric data, and list of ingress/egress times for major world cities (PDF). From US Naval Observatory.
http://www.hmnao.com/nao/transit/V_2012/index.htmlLocal circumstances of the 2012 transit of Venus for observers in the United Kingdom. From HM Nautical Almanac Office.
World visibility map of 2012 transit of Venus; from A Popular Account of Past and Coming Transits, by Richard Proctor; 1882.
http://www.royalsociety.org.nz/2010/12/03/2012-transit-of-venus-plans/#from-the-transit-of-venus-project-group
Tolaga Bay – Uawa will host international celebrations for the Transit of Venus in June 2012.
http://www.sydneyobservatory.com.au/2011/transit-of-venus/
Sydney Observatory will have special programs available on 6 June 2012.
Six Ways to See the Transit of Venus
1 As suggested in the NASA guidelines above, the use of eclipse shades or of #14 shade welding glass 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 will not be discernible. At one minute of arc in size, Venus is near the visual limit of most people's eyes. It's tiny compared to the sun, which is about 32 arcminutes in diameter.
Eclipse Shades or Solar Shades appear similar to sunglasses, but they have a special filter that permits safe viewing if the filter is in new condition. Eclipse/solar shades are available through Rainbow Symphony and other retailers listed at http://www.mreclipse.com/Totality/TotalityApC.html under "Solar Filters." Before looking at the sun, inspect the material to make sure the lenses are not scratched or compromised in any way. If so, discard the shades.
YES!
Dr. B. Ralph Chou, author of Eye Safety and Solar Eclipses cited above, suggests "one of the most widely available filters for safe solar viewing is shade number 14 welder's glass." It is imperative that the welding hood houses a #14 or darker filter. Do not view through any welding glass if you do not know or cannot discern its shade number. Be advised that welders typically use glass with a shade much less than the necessary #14. Just because the hood makes the sun somewhat more tolerable to see does not mean the welding glass is of the proper kind.
The view through a proper #14 welding glass (left) shows only the sun, which will appear green. The surrounding landscape is not visible.A welding glass that is less than shade #14 allows too much light to pass. In the picture at right, an insufficient welding glass permits so much light to pass through that the landscape can be seen. This view is not safe.
TIP: Because the view should be dark, you essentially want your eyes to adapt to the darkness as if you were seeking night vision. With your body facing the sun, look down toward your feet and hold the #14 welding glass near the bridge of your nose. Slowly raise your head to meet the sun, with your eyes continuously protected by the proper filter. If you simply look toward the sun and then raise the glass in place, your eyes will need time to adjust to the sudden darkness and will be unnecessarily exposed to the sun, even if only briefly.
NO!
Do not be lulled into thinking that you can look safely at the sun while wearing sunglasses, for sunglasses do not protect your eyes sufficiently. So don't try it!
Image courtesy of Sarah.
2 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 will not be discernible.
Dr. Hugh Hunt demonstrates a successful pinhole projection (right) of the 2004 transit of Venus at http://www2.eng.cam.ac.uk/~hemh/transit.htm. Additional instructions for pinhole projectors are at http://www.exploratorium.edu/eclipse/how.html; from the Exploratorium.
3 You may project a magnified view of the sun through a telescope onto a white surface, which conveniently allows a larger number of people to watch concurrently. See http://www.popastro.com/sections/solar/chap3.htm for instructions for projecting the sun with a telescope, along with solar activities like sunspot counting; courtesy of the Society for Popular Astronomy.
The projection technique often has its own limitations. Because magnified projections usually have an exposed focal point beyond the eyepiece, a bystander can inadvertently put her eye or body in the sight line of the sun. Hence, a projecting telescope must not be left unattended. (See Unattended Equipment Hazards, left column.) Large reflector telescopes can generate too much heat by concentrating a lot of the sun's energy on the secondary mirror and eyepiece, so the incoming light must be attenuated first. "Stop down" the aperture. Likewise, SCT or Schmidt-Cassegrain telescopes can experience too much heat build-up as the light bounces internally.
Hubert van Hecke provides the design and instructions for making his sunspotter. Additional pages at his Ask Mr. Science web page indicate how to take sunspot data and analyze them.
The Exploratorium demonstrates how to view a planet in transit safely by projecting the image of the sun with binoculars. Important: Do not look at the sun through binoculars without solar filters on the large ends of both the barrels. Do not leave this rig unattended.
4 The safest method for allowing a large crowd to witness the transit of Venus concurrently is to project a magnified image through a closed-loop device.
A popular projection device used during the 2004 transit of Venus was the now-improved Sun Funnel. Made from simple materials (a plastic funnel, a clamp, an eyepiece, and some projection fabric), the device fits in your telescope like an eyepiece with an appendage. A clear image of Venus transiting the sun appears on the screen. Because the entire light path is enclosed, observers are not at risk. A larger version of the screen uses a bucket to yield a larger image. Download simple instructions and supplies list written by AAS Press Officer Richard Tresch Fienberg.
Bruce Hegerberg's design for a Sun Gun is online at http://web.mac.com/picinapod/Sun_Gun/SUN_GUN.html
Another viewing tool is Gene Zajac’s modified version of a Sun Gun (see 1999 GLPA Proceedings). The device safely allows a crowd of spectators to view a large projection of the sun, the transiting planet, and sunspots.
The Sunspotter is commercially available from Science First. It provides a surface on which you can safely trace the sun's outline and sunspots onto a piece of paper.
TheVenuscope and solar shades are commercially available from SODAP-SOBOMEX- Department Sky & Space.
http://www.solarscope.com/
A Solarscope is commercially available from [Light Tec Optical Instruments]
5
The transit of Venus is perhaps best viewed directly when magnified, which demands an appropriate solar filter over the large end of the telescope. Often made of glass or Mylar, these "white light" filters block about 99.99% of the incoming sunlight, which allows the eyepiece then to magnify the image. A filtered, magnified view will show the sun (either blue or orange), the planet Venus, the "black drop" effect, and sunspots. See Solar Filters or http://skyandtelescope.com/observing/objects/sun/article_101_1.asp for a list of retailers.
Note #1: The sun's immense energy must be drastically reduced before it enters the telescope. Do not use small filters that fit over the eyepiece (as found in some older, cheaper telescopes), for the concentrated sunlight can shatter them.
Note #2: Remove unfiltered finder scopes so they are not inadvertently accessed. Do not rely on a lens cap--even if it is taped on--to keep the eyes of a prying person at bay. (See Unattended Equipment Hazards in left column.)
BinoMite Solar Binoculars are commercially available from Coronado Technology Group.
Special telescopes with built-in hydrogen-alpha filters show additional solar features, such as the sun's surface granulation and prominences extending outward into space.
6 Transit not visible from your location? Watch the live webcast from the fun team at NASA EDGE. Details to follow.