MISSOULA, Mont. - For just over 3 hours on Tuesday morning there will be a cosmic show over Montana.
The first of four total lunar eclipses during the next 18 months takes place early Tuesday morning. The eclipse starts at 11:58 p.m. Monday night and ends at 3:33 a.m. Tuesday. The middle of the eclipse, when the entire moon is a deep red, is at 1:45 a.m.
A lunar eclipse occurs when the moon's orbit takes it into the earth's shadow. It's a perfect alignment between the sun, earth and moon.
It turns the moon dark red because the only light that reaches the moon during the eclipse first passes through the earth's atmosphere. The air scatterers the sunlight and separates into different colors. The red light makes it through the scattering process and reaches the moon. It's the same reason sunsets appear red.
University of Montana professor Dan Reisenfeld told us, "At that particular moment, the only light reaching the moon is all of the sunrises and all of the sunsets on earth all at once."
A total lunar eclipse is when the entire moon passes through earth's shadow. Four total lunar eclipses in a row is called a tetrad. Eclipses come in predictable cycles, around every six months, but most eclipses have only part of the moon cloaked in shadow; so little that many don't notice.
Reisenfeld states that lunar eclipses are often linked to solar eclipses. Many fall within two weeks of each other. Solar eclipses are much harder to spot. They're only visible in a swath over a couple hundred miles.
A lunar eclipse is visible over whatever continents happen to be at night when the eclipse occurs. For Montana all four of the upcoming tetrad of eclipses will be visible. The second eclipse occurs on October 8.