November 8, 2006
What is a Transit?
A transit occurs when a planet crosses the line of sight between the Earth and the Sun. From Earth, we see a small circular dot on the face of the Sun, caused by the planet's shadow.
From Earth, only transits of Mercury and Venus are possible, because they orbit closer to the Sun than does the Earth. The outer planets (Mars, Jupiter, Saturn, Uranus and Neptune) are all farther from the Sun than Earth, and so they can never get between us and the Sun.
There is another celestial body that can cross between the Earth and Sun and cast its shadow on Earth: our Moon. Because the Moon is so close, it appears very large in our skies and completely blocks the Sun. For this reason, we call this event an eclipse. But the principle behind eclipses and transits are the same.
What Makes this Transit Special?
This is the first time Mercury has transited the Sun since 2003. This is a relatively rare occurrence. There are approximately 13 transits of Mercury each century. The next transit of Mercury will not occur until May 9, 2016.
The transit features four distinct events, as Mercury's disc moves into and across the face of the Sun:
- First Contact, at 11:12 am, occurs when Mercury's disc first touches the Sun's disc. Mercury's disc has not fully moved in front of the Sun yet.
- Second Contact, at 11:14 am, occurs when Mercury's disc has moved fully in front of the Sun, but the edges of both discs are still touching.
- Third Contact, at 4:07 pm, occurs when Mercury's disc starts to move off the Sun's disc.
- Fourth Contact, at 4:09 pm, occurs when Mercury has fully moved off the Suns's disc, but the edges of both discs are still touching.
Viewing the Transit in the SF Bay Area
Here in the San Francisco Bay Area, you can view the transit at the following locations:
San Francisco - Randall Museum
From 11am until 1pm, the event is open for children and schoolgroups only. Sessions in the Randall Museum auditorium, as well as special educational activities will introduce children to the Sun and planets. Solar telescopes available for children to view the transit as it happens. From 1 pm until the 4 pm, the event will be open to the general public to view the transit.
The Randall Museum will also display a live feed of the Exploratorium webcast for guests, which is open to everyone.
San Francisco - Exploratorium
Oakland - Chabot Space and Science Center
The Chabot Space and Science Center will offer free viewing of the transit with paid admission.
Pleasant Hill and Walnut Creek - Mount Diablo Astronomical Society
The Mount Diablo Astronomical Society has one public event and 3 private events scheduled for the Mercury Transit on Nov 8. The public event is from 11am to 5pm at Diablo Valley College on the grass by the Library, next to parking lot 3. For more info, contact email@example.com or visit http://www.mdas.net.
San Mateo - San Mateo County Astronomical Society
The College of San Mateo together with the San Mateo County Astronomical Society (SMCAS) will be hosting an event from the new rooftop observatory at College of San Mateo. The public is invited to join students, faculty, staff, and members on Bldg. 36, 4th floor on the College of San Mateo campus. For directions and parking information visit: http://www.collegeofsanmateo.edu/astronomy/ or call: 650-574-6272.
Santa Clara - The Astronomy Connection
Michael Swartz of the Bay Area Astronomy Connection is planning on setting up his refractor telescopes and solar gear in the main courtyard by the main fountain at the Santa Clara civic center. It is right by the IT department office and also right next to the cafeteria. He will be there from around 10:30am until the transit completes.
San Jose - San Jose Astronomical Association
The San Jose Astronomical Association is sponsoring free public viewing of the transit at Houge Park in San Jose, near Campbell and Los Gatos.
Salinas - Fremont Peak Observatory Association
The Fremont Peak Observatory Association (FPOA) is offering public viewing of the transit on the campus of the Hartnell Community College in Salinas in front of the campus planetarium.
Auburn - Starry Starry Nights
A group of astronomers (Starry Starry Nights) will be setting up telescopes to show the transit from 11:30 AM about 4 PM for free public viewing.
Location is in Auburn, about 40 miles above Sacramento, (along highway 80) at a park known as the American River Canyon Overlook Park (also known as the Auburn Skate Park).
Directions: To get there, go to downtown Auburn, to the historic Courthouse. One of the roads branching from there is Auburn-Folsom Rd. Take that east to the third stoplight (about a mile). This is Pacific Avenue. Turn left. Go about 0.8 mile to the Auburn Dam Overlook, which is on your right. We set up at the far (east) end of the parking lot.
Here is the local information for the SF Bay Area, courtesy Dr. John Westfall of the Association of Lunar and Planetary Observers:
- Click here to view a detailed diagram showing the details of the transit, including its path across the sun.
Viewing the Transit Yourself
You can also view the event yourself, if you have the proper equipment. Since Mercury is only 1/194 of the Sun's apparent diameter, we recommend a telescope with a magnification of about 50x to 100x to observe the event.
Because you will be viewing the Sun, you must equip your telescope with a filter for safe solar viewing (example illustrated in photo), or use a dedicated solar telescope designed solely for safe sun viewing.
Never, ever look directly at the Sun without proper eye protection, or you can cause permanent blindness or eye damage.
Do not use a conventional finder scope to aim your telescope at the Sun. In fact, make sure any finder scopes are either covered or removed, to avoid the possibility someone may look through them by accident.
If your telescope is not equipped with a computer which can locate the Sun, aim your telescope by looking at the shadow it casts on the ground. When the shadow is smallest, the scope is pointed at the Sun. Use a low-power eyepiece to help you initially find your view of the Sun, then switch to a high-power eyepiece to observe.
For More Information
The following web sites have more information on the transit.
- Imaginova (an astronomical software publisher) has produced this nice six-page guide to viewing the Mercury Transit that you can download and print.
- This NASA webpage has an excellent animation of the transit, plus information on the planet Mercury.
- The NASA Eclipse Website is the most authoritative source of information on the transit.
- NASA Sun-Earth Day transit webcast - November 8, 1:30 - 2:30 ET (10:30 -11:30 PT) - Featuring:
- Panel of scientists live from NASAs Goddard Space Flight Center with an additional panel of educators and amateur astronomer live from Langley Research Center.
- NASA Explorer Schools connected for live interaction-questions and answers.
- A telescope 'safety viewing' demonstration with instructions on how to view the transit using a classroom solarscope.
- Live images of the transit from 2 NASA satellites, SOHO and TRACE.
- Live ground based images from Kitt Peak and Hawaii!
- Mercury transit Hawaiian style - live webcast from Hawaii
- Wikipedia online encyclopedia page on the transit.
- Exploratorium webcast -from Kitt Peak National Optical Astronomy Observatories. Public can also view the transit in Exploratorium webcast studio. Staff physicist Paul Doherty will speak at 11am. Event is free with admission to Exploratorium.
- Randall Museum http://www.randallmuseum.org/
- Live webcast of the Transit of Mercury at http://nasadln.nmsu.edu/dln (NASA Digital Learning Network) will include discussion of the science, technology, and history of the transit as well as our knowledge of the Sun and space weather. The webcast will include a panel discussion about Mercury, the Sun and safe viewing techniques of the transit. There will be a live feed (provided by the Exploratorium) of the transit from Kitt Peak National Observatory near Tucson, Arizona, beginning at first contact.
- Article on Mercury Transit for general audiences written by Suzanne Gurton from the Astronomical Society of the Pacific, written in English and Spanish:
- Kepler transit pages