Of the many objects to observe in the night sky, amateur astronomers often seek out the planets. Unlike the distant stars, which appear only as points of light in even the biggest telescopes, the planets show round disks and cloud features to an observer with a small telescope. You can observe any of the seven planets (Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune) with any size of telescope, although the higher magnification and quality telescopes will give you the best view.
Choose a planet to observe. Check rising and setting times for your location to see which planets are visible when you want to make your observations.
Find the location of your planet at the time of your observations. Online sky almanacs can tell you the location (by constellation), altitude and azimuth (distance from north) of a planet at any given time.
Locate the planet in the sky. For the visible planets (Mercury, Venus, Mars, Jupiter and Saturn), you should be able to locate the planet using a star chart and your eyes. Look for a bright object that does not appear to twinkle as much as the surrounding stars, then compare its location to your star chart. If the object does not appear on the chart, it is a planet.
Point your telescope at the planet. Use your telescope’s finder--the small telescope attached to the outside of the telescope tube--to aim and then adjust through the main scope. If you can change the magnification on your telescope, start at a lower magnification to find the planet, then switch to higher magnifications for the details.
Use the edge of the planetary disk to focus your telescope. The circular edge should be sharp and clear when the telescope is correctly focused.
Adjust your telescope to compensate for the sky’s apparent motion. Because the Earth rotates, the sky appears to shift position over time. When using a telescope, this motion will swiftly move the planet out of your view. Telescope drive motors can match this motion, or you can move the telescope by hand every few minutes.
If you have a good, steady telescope, Jupiter and Saturn offer the most impressive views. Even a small telescope (such as a 4-inch reflector) can show you Jupiter’s Great Red Spot or Saturn’s rings. You can also look for Jupiter’s four largest moons. Use a red-colored flashlight to consult your charts and to adjust the telescope. Red light will not hurt your night vision as much as white light.
Uranus and Neptune, while observable with a telescope, are not visible to the naked eye. You will need accurate coordinates and a good knowledge of finding coordinates in the sky to locate these planets. However, even in a telescope, you should not expect to see much detail. Mercury and Venus always remain close to the Sun in the sky. Because of the brightness at dawn and dusk, telescopes may have only limited use in observing these planets.