Seth Jarvis, director of Clark Planetarium, was explaining the view as Margaret Nordy peered through one of the telescopes set up near the splashing Olympic Fountain at The Gateway.
"That's the sun?" asked Nordy, a Salt Lake City resident.
"That's the sun," he replied.
"I'm not seeing the whole thing then," she said.
Jarvis explained that the sun is too large to show up in a telescope eyepiece at that magnification.
Under magnification and seen through a safe solar filter that covered the end of the telescope, the sun appeared as a light section with a curving edge. A small splotch was a sunspot. A much tinier dot was the planet Mercury.
Nordy said she could hardly believe she was looking at the sun.
Clark Planetarium and the Salt Lake Astronomical Society had established sites where people were treated to free, safe views of a transit of Mercury — the crossing of the innermost planet across the face of the sun, as seen from Earth. The sites were several locations in The Gateway and the Harmons store in Midvale.
Jarvis estimated about 200 got a look Wednesday at the diminutive planet and relatively vast star as the transit unfolded.
Mercury's trek across the face of the sun started shortly after noon and continued until sunset, though at The Gateway the project was over around 3:30 p.m. when the sun slid behind nearby buildings.
Transits of Mercury happen only 13 times a century. The last time one was visible from Utah was in 1999.
"Mercury is traveling directly in front of the sun. It's not going to be visible again until 2016," Jarvis told a small crowd.
Jarvis explained that the sunspot cycle recently passed solar minimum, when it is least active, and that the number of sunspots is increasing.
Sunspots are so small that a person using a proper solar filter, but no telescope, could rarely see one. The one visible on Wednesday was larger than Earth. Mercury was far smaller than the sunspot.
Mercury is about 3,000 miles across, compared with Earth's 8,000 miles. So the littlest planet is about a third as far across as this globe.
Steve Shindle, a visitor from Buckley, Wash., took a look and said, "Oh, I think it's fantastic. I was so glad I had a chance to see it."
His wife, Karla Shindle, added, "It's like a period after a sentence. So small — like a grain of sand."
Developer Kem Gardner took a gander and said, "It looks like it wasn't 3,000 miles across. That little spot, though — it was perfectly round."
"I think it was cool, very cool," said Deborah Bayle Nielsen, president and CEO of the United Way of Salt Lake, Davis, Summit and Tooele counties. "It just shows the size of the sun by comparison.
"It looked like a pinpoint and it's 3,000 miles across. It just brings home the size of the sun."