Idaho Skies Transcript for September 13th and 14th

RACHEL
Welcome to Idaho Skies for September 13th and 14th. We’re your hosts, Rachel...

PAUL
...and Paul.

RACHEL
Hey, the moon reaches its last quarter phase on the 13th.

PAUL
So astronomers divide the moon into fourths?

RACHEL
Not really. They only divide the moon’s path across the sky into fourths.

PAUL
Every time the moon travels 90 degrees across the sky, the moon enters a new quarter

RACHEL
And the moon’s appearance also takes on a new shape at each quarter.

PAUL
It all starts when the moon is it’s closest to the sun.

RACHEL
The moon is invisible at this time because of the sun’s glare.

PAUL
And because its sets at around the time of sunset.

RACHEL
Roughly, a week later, the moon will travel 90 degrees away from the sun.

PAUL
Sunlight is always illuminating half the moon’s surface.

RACHEL
But only half of that illuminated surface faces directly towards Earth at first quarter.

PAUL
That gives the first quarter moon its half circle shape.

RACHEL
Prior to first quarter, the moon had a crescent shape.

PAUL
That’s because sunlight illuminated most of the lunar farside, or the side we can’t see.

RACHEL
Some people get confused and think the moon’s crescent shape occurs when Earth casts a shadow on it.

PAUL
But it’s actually because we can only see a thin sliver of the moon’s illuminated surface.

RACHEL
As the moon works its away around it, the moon’s illuminated portion also works its way around the surface.

PAUL
Letting stargazers see more the moon in daylight.

RACHEL
And changing the moon from a thin crescent to a fully illuminated moon at full moon.

PAUL
That’s Idaho Skies for the 13th and 14th of September.

RACHEL
Be sure to follow us on Twitter at Idaho Skies for this week’s event reminders and sky maps.

For Idaho Skies this is Rachel...

PAUL
...and Paul.

RACHEL
Dark skies and bright stars.