The Stages of the Transit of Venus Explained

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Paul Hyndman captured this stunning view of Venus crossing the face of the sun in hydrogen-alpha light on the morning of June 8, 2004 from Roxbury, Connecticut. He used an Astro-Physics 105-millimeter Traveler telescope fitted with a Coronado Solarmax90/T-Max and 30-mm blocking filter, a TeleVue 2X Powermate lens, and an SBIG STL-11000M CCD camera.
Paul Hyndman

THE GIST

— The stages of today's rare sun crossing start when the leading edge of Venus first touches the solar disk.

— Astronomers use special solar filters on telescopes to view the sun safely.

— Contact II, or ingress interior — the moment when Venus moves fully onto the sun's face is the second stage.

Today's historic Venus transit is a marathon event lasting nearly seven hours, but skywatchers who don't have that kind of time can break it down into a handful of key milestones.

Venus treks across the sun's face from Earth's perspective today (June 5; June 6 in much of the Eastern Hemisphere), marking the last such Venus transit until 2117. Few people alive today will be around to see the next transit, which makes the rare celestial sight a premier event in the astronomical and skywatching communities.

Wide Angle: The Transit of Venus 2012

The Venus-sun show will begin around 6 p.m. EDT (2200 GMT) and end at roughly 12:50 a.m. EDT (0450 GMT) Wednesday, with the exact timing varying by a few minutes from point to point around the globe.

First contact

Before you even attempt to observe the transit of Venus, a warning: NEVER stare at the sun through binoculars or small telescopes or with the unaided eye without the proper safety equipment. Doing so can result in serious and permanent eye damage, including blindness.

NEWS: How to Photograph the Transit of Venus

Astronomers use special solar filters on telescopes to view the sun safely, while No. 14 welder's glass and eclipse glasses can be used to observe the sun directly. [How to Safely Photograph the Venus Transit]

With that warning stated, here's a look at the first major stage of the transit of Venus.

The transit officially commences when the leading edge of Venus first touches the solar disk, an event astronomers call "Contact I" or "ingress exterior." This milestone occurs at 6:03 p.m. EDT (2203 GMT) for observers in eastern North America, while skywatchers on the other side of the continent will see it a few minutes later, at 3:06 p.m. PDT.

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