John Foos, age 14, of Rochester, New York, for his question:
How can you tell stars from planets through a telescope?
In Andy's opinion, every student deserves a chance to view the heavens through a telescope. Even a beginner's instrument stretches the mind and brings endless delight to the beholder. But such wondrous excitement sparks the old curiosity and sooner or later the observer wants to know just what he or she is beholding. This is the time to consult the masses of astronomical data gathered by patient observers through the past 5,000 years or so.
The first trick is to focus your field of vision on one certain heavenly body. It is helpful to know its location in relation to the rest of the celestial parade because, if all else fails, this can help you to identify it. However, if by chance you focus on an interesting stray object, there are ways to tell whether it is a star or a planet. A telescope reveals a star as a point of shining light. Even the most powerful telescopes reveal stars as points of light, though their different colors may shine more distinctly.
So, if the view through your telescope reveals a point of light, you are gazing at a star. The planets are seen as flat discs or partial discs. Venus and Mercury show changing phases like those of the moon because they are closer to the sun than tae are. The outer planets reveal complete discs because they are closer to the sun and see only theirdaylight sides. However, each of the planets presents a different picture and we soon recognize them as old friends.
The best way to get acquainted is to study one of those delightful astronomy magazines published for amateur star gazers. Failing this, we can consult the monthly astronomy charts, published in almanacs and sometimes in newspapers. The object is to learn which planet is where at what time on each date. Locate it visually, then focus it on your telescope field. Whatever planet it happens to be, you will recognize it the next time your telescope chances to spot it.
Venus is a bright blur of golden light that goes through lunar type phases as it circles the sun. Mars is blotchy red, revealing, one and sometimes two of its white polar caps. Jupiter is rather flat and banded with lighter and darker pastel colors.
A clear viewing may reveal an oval red spot on one side, or up to four little orbiting 3ovian moons. Saturn is a flattened disc distinguished by circles of golden rings. With lots of luck you may locate Uranus, which looks like a pale greenish disc.
The planets soon become old friends, though it helps to check their positions because they wander around the sky. All of them reveal more fascinating detail than bright pin pointed stars. However, other objects may enter the scene. Once in a while a meteor may flash across the field or a rare comet. But the most likely strangers are sure to be the man made satellites orbiting the earth but that is another story.