If Tuesday's weather is good, the transit of Venus will look like a small black dot moving slowly across the sun.
It's the last time Venus will come between the earth and the sun in our lifetime.
“If you want to see a planet transit the sun, now is the only time in your life to see it,” said Evan Zerby, Ames Area Amateur Astronomers community outreach director.
Venus last came between the earth and the sun in 2004 and will again about 5 p.m. Tuesday. But the next crossing takes place in 2117.
Ames Area Amateur Astronomers club has planned a viewing event in McFarland Park for thousands for the once in a lifetime event. Organizers said to bring a lawn chair. Solar glasses must be worn to watch the transit, but if you don't have them now, it's probably too late to find a pair, Zerby said.
The club has ordered 100 pairs of solar viewing glasses from England, which will likely have to be shared. People will also be able to take turns watching the solar event through a number of filtered telescopes and solar scopes. The club will also offer NASA broadcasts of the event in the park's shelter. One will come from the Mauna Kea Observatory in Hawaii, the best place to watch this transit on earth and the other from the Solar Dynamics Observatory, a satellite in space.
The club event begins at 3 p.m. with a scale-size walking tour of the solar system through McFarland Park. (A map of the tour is attached to this story.) The actual transit will start at 5 p.m. and end after sundown. The park and public event closes at 9 p.m. but Zerby expects some people to stay until it's over, sometime around midnight.
If you can't make it to the park but still want to watch, the club has offered viewing advice on its website.