BULLHEAD CITY — What color is the Moon?
Probably not the color you think it is, says Jim Patterson.
Patterson, a library assistant in Lake Havasu City and self-described “amateur astronomer,” gave a presentation Friday afternoon on astronomy at the Bullhead City library.
He said his goal was to arm attendees with tools they can use when stargazing with the naked eye.
He began with a lesson on parallax — the difference in the apparent position of an object viewed from different perspectives. That, he said, explains the difficulty one can encounter when trying to direct another person’s gaze toward a celestial object.
He showed a picture and asked those in attendance whether they saw an old woman or a young woman.
He then told the audience it was a picture of neither.
“It’s a purposely drawn image that’s leaving out information,” Patterson said. “Your brain tries to fill in what’s missing.”
He said the same thing happens with the night sky. Our eyes tell us that there are large and small stars up there, and that some are dim and some are bright.
Patterson said that in reality, each of the stars should appear as a tiny point in the sky; the reason they don’t is because some of them are much brighter, and we see that brightness as greater size.
Patterson led a series of exercises that illustrated the way human eyes adjust to variations in light conditions. He projected on a screen what appeared to be a white circle.
Patterson explained that the eye decides to see the circle as white because of its relative brightness compared to the background. Projecting an area of white space surrounding the circle made it appear black.
This also was an illusion, revealed when Patterson filled the remainder of the screen with black. The circle was actually a dark gray.
Patterson said the same thing happens when we look at the moon. Luna is actually “the color of worn asphalt,” he said, and its relative brightness makes it appear white.
He discussed magnitude with the audience and then provided a few stargazing tips.
Key will be locating Polaris, the North Star. It lies due north for everyone north of the equator, and can be used as a reference point for spotting other sights in the sky. Patterson said the night sky rotates around a central axis, meaning that a star will always be in the same position relative to Polaris, although it will appear in different parts of the sky throughout the year.
Patterson demonstrated how to use the body in astronomy, pointing one arm straight up to mark the zenith and the other forward to denote the horizon.
He suggested the following guidelines for measuring angles:
• The width of one pinky finger (1°).
• The combined width of the three middle fingers (5°).
• The width of a fist (10°).
The width of a hand with the index and pinky fingers extended and the others folded over the palm (known colloquially as “devil horns”) (15°).
• The width of a hand with the thumb and pinky finger extended and the others folded over the palm (the “Shaka Sign”) (25°).
He then showed how to find such familiar sights as the Big and Little Dippers and discussed how to tell time by the stars.
In response to a question about astronomy in the day of Galileo Galilei, Patterson said observers could detect a lot less of the universe than modern technology permits.
“If you have a pair of binoculars, you basically have his telescope,” Patterson said.
Jim Legendre of Bullhead City said he has taken astronomy courses, and that he and his wife, Denise, found Patterson’s presentation informative.
“I never realized you could put your finger up and actually ... tell where the stars are and how far apart,” Legendre said.
Mark Yarbrough of Bullhead City said the presentation was a great introduction for people looking to learn more about astronomy. He and his wife, Mary soon will take a trip to Rye, Arizona, during which they will take advantage of the relative lack of competing light from earth to get a good look at the solar system.
Patterson said he wanted audience members to leave with knowledge of how simply one can get into astronomy.
“They don’t need a lot of fancy equipment,” he said. “They can figure out a lot just with the body they have.”