DeKALB | Mercury passed through the sun’s path for the first time since 2003 Wednesday.

The transit began a little after 1 p.m. and remained visible for about four hours.

Eric Johnson, a junior applied physics major, was at the Davis Hall observatory looking for Mercury to enter Earth’s field of view on the observatory telescope and cameras.

“Basically, it’s lapping us. If you kind of think of it that way, because it’s going faster around the sun than we are,” Johnson said.

Mercury and Venus are the only planets that transit the sun because they are closer to it than Earth. Mercury does this about 13 times every century. The next time Mercury is expected to transit will be in 2016. The planet can first be seen around the edges of the sun and will pass across the disc of the sun.

The transit is comparable to a solar eclipse, though it is much farther away and more rare than an eclipse, Johnson said.

He is pleased the transit occurred while he is still at NIU.

“It’s nice to have access to the observatory and see this, especially since it’s so rare,” he said.

Finding Mercury passing the sun on the observatory cameras can be a difficult task, since it is so much smaller than the sun — about 1/194 its size, according to NASA’s Web site — but the equipment in the observatory makes it easier to locate, even if it is a guessing game trying to find the exact spot, he said.

“It takes a while to find it, but usually it’s worth it when I do,” he said.