Venus is going to move across the face of the sun this afternoon in a rare celestial event, but the weather may not cooperate.
Forecasters are calling for a 90 percent chance of clouds when the transit of Venus begins at 3:09 p.m.
The skies are likely to stay cloudy and could bring rain showers throughout the event, which lasts until sunset in this region.
The next transit of Venus won’t happen until 2117.
An eclipse of the sun on May 20 was hampered by clouds across the region, although some viewers locally reported seeing part of the eclipse when the skies parted slightly.
Members of the Spokane Astronomical Society are keeping their fingers crossed. They are setting up three public viewing locations – two in north Spokane and one at a private residence in the north part of Spokane County.
The society and its members have telescopes and viewing glasses that allow people to safely look directly at the sun.
Venus will appear as a small dark spot moving slowly across the face of the sun as part of its normal planetary orbit. The transit will take six hours and 40 minutes, ending after the sun has set in Eastern Washington and North Idaho.
The midpoint of the transit, known as greatest transit, occurs at 6:29 p.m.
A similar transit in 2004 was not visible in Spokane.
The orbit of Venus is inclined 3.4 degrees with respect to the Earth. The transit occurs when Venus crosses the plane of Earth’s orbit at the same time that Venus passes inferior conjunction, the point that marks Venus’ closest pass of the sun from the perspective of Earth.
Transits of Venus are so rare that astronomers believe this event will be only the seventh time humans have viewed the passage through telescopes, starting in 1639, according to the astronomical society.
The transits of Venus follow a predictable cycle that lasts 243 years.
This transit is the second in the past eight years. Venus won’t cross the face of the sun for 105.5 years.
After that, a pair of transits will occur eight and 16 years later, to be followed by a period of 121.5 years before another transit.
Astronomical society members will be set up at the east parking lot of River Day School, 116 W. Indiana Ave., and the south end of Franklin Park along Queen Avenue west of Division Street.
In addition, society member Coy Fullen is opening his observatory to the public. He lives at 24006 N. Rose Meadow Lane in the Colbert area.
To get there, take U.S. Highway 395 north toward Deer Park and turn left on Wild Rose Road. Go about a half mile to Rose Meadow Lane and turn right. Fullen’s residence is on the right.