Therefore, if you use the 20mm eyepiece your magnification is 700/20 = 35x. The same formula can be applied to any of your eyepieces.
Celestron offers numerous optional eyepieces to expand your range of magnification. Eyepieces come in barrel diameters of .96" and 1¼". In general, 1¼" eyepieces are of a higher optical quality and give you sharper images, along with a wider field of view and better eye relief.
Magnification through the telescope has its limits. These limits are determined by the laws of optics and the nature of the human eye. The maximum usable power (with sharp images) is equal to 60 times the aperture of the telescope (in inches). So, with a 60mm telescope it has a maximum useful power of 144x (2.4" x 60) and with the 70mm the maximum is 165x (2.7559 x 60). Most of your viewing will be done in the range of 30x to 120x. Higher powers are used mainly for lunar and sometimes planetary observing where you can greatly enlarge the image. The images at extremely high powers like 675x magnify the image bur remember that the contrast will be very low and the image somewhat blurred due to the super power. For the brightest images with the most contrast, use the lower powers with a smaller image scale.
TELESCOPE OPERATION — ASTRONOMICAL OBSERVING
Now that your telescope is set up, you’re ready to use it for observing.
Observing the Moon
In the night sky, the moon is a prime target for your first look because it is extremely bright and easy to find. Although the beauty of the full moon may make it seem a perfect viewing object, in fact, the light reflected from its fully illuminated face can be overpowering. In addition, little or no contrast can be seen during this phase.
One of the best times to observe the moon is during its partial phases, such as a crescent or quarter moon. At these times, long shadows reveal a great amount of detail on the lunar surface. At low power, with the standard eyepiece, you’ll be able to see the whole lunar disk at one time. Change to higher power (magnification) to focus in on a smaller area.
Keep in mind that the rotation of the earth will cause the moon to drift out of your field of view. You’ll have to manually adjust the telescope to keep the moon centered. This effect is more noticeable at higher power. Consult a current astronomy magazine or your local newspaper to find out the current phase of the moon.
Lunar Observing Hint
To increase contrast and bring out visible detail on the lunar surface, try using different eyepiece filters (available through your local Celestron dealer). A yellow filter works well for improving contrast.
Observing the Planets
Other easy targets include the five “naked eye” planets of our solar system, so called because they can be spotted in the night sky by the unaided eye. You can see Venus go through its
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