Idaho Skies Transcript for November 30th and December 1st and 2nd

RACHEL
Welcome to Idaho Skies for November 30th and December 1st and 2nd. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
The moon is rapidly approaching new, so stargazers only have a few more days to see it.

PAUL
The waning crescent moon will be visible in the low east before sunrise, so stargazers will need to rise early enough to see it. Not only will the moon appear as a thin crescent, its dark portion will be covered with an ashen light. That illumination is called earthshine and it’s the result of sunlight reflecting off of Earth’s bright clouds. An astronaut standing on the dark portion of the moon would see a large and mostly full Earth shining light upon the lunar surface.

RACHEL
Use your binoculars when looking for earthshine. They’re useful not only because of their magnification, but because of their light gathering ability. The human pupil can reach about ¼ of an inch in diameter. So that’s the greatest amount of light they can admit to our retina. Binoculars on the other hand have lens two inches across. All that light gets concentrated into a region less than ¼ inch across.

PAUL
Since binocular lenses are eight times wider than our pupil, they gather eight-squared or 64 times more light than our eyes can unaided. It’s their ability to gather more light than our eye that makes them so useful for astronomy. In fact, many astronomical objects are plenty large enough. It’s that they’re so faint to makes them difficult to see. So just imagine what the 200-inch mirror on Mt. Palomar could do for your vision.

RACHEL
Just by coincidence, the glass for the 200-inch mirror was poured into a ceramic mold 84 years ago on the 2nd. The glass is actually Pyrex, a glass recipe designed to minimize expansion due to temperature changes. It took over 11 months to cool the glass down enough that it could be ground into a telescope mirror. But World War II intervened and prevented the completion of the telescope until 1947.

PAUL
That’s Idaho Skies for the 30th of November and the 1st and 2nd of December.

RACHEL
Be sure to read our blog for additional information. It’s at idahoskies.blogspot.com.

For Idaho Skies this is Rachel…

PAUL
…and Paul.

RACHEL
Dark skies and bright stars.