MAGNIFICATION (POWER)

The magnification (or power) of a telescope is variable depending upon the focal length of the eyepiece being used along with the focal length of the telescope. In equation format, the formula looks like this:

Magnification = FL(telescope)

FL(eyepiece)

To determine the magnification using the standard 20mm eyepiece, simply divide the focal length of your telescope by the focal length of the eyepiece (20mm). For example, dividing the focal length of the Firstscope 90 (1000mm) by 20mm yields a magnification of 50 power.

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 is equal to 60 times the aperture of the telescope (in inches). For example, using the 70mm model (2.8") then your maximum useful power is 168x (2.8" x 60). You can create power higher than this limit but the images will be dark and blurred with poor contrast.

The maximum power is used only under ideal conditions which are not common. Most of your viewing will be done in the range of 25x to 120x. Higher powers are used mainly for lunar and planetary observing under ideal seeing conditions.

Determining Field of View

Determining the field of view is important if you want to get an idea of the angular size of the object you are observing. To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer) by the magnification. In equation format, the formula looks like this:

Apparent Field of Eyepiece

True Field = 

Magnification

As you can see, before determining the field of view, you must calculate the magnification. Using the example in the previous section, we can determine the field of view using the same 20mm eyepiece. The 20mm eyepiece has an apparent field of view of 45°. Divide the 45° by the magnification, which is 50 power. This yields an actual field of .9°, or almost a full degree.

To convert degrees to feet at 1,000 yards, which is more useful for terrestrial observing, simply multiply by 52.5. Continuing with our example, multiply the angular field .9° by 52.5. This produces a linear field width of over 47 feet at a distance of one thousand yards. The apparent field of each eyepiece that Celestron manufactures is found in the Celestron Accessory Catalog (#93685).

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Celestron 70 manual Magnification Power
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70 specifications

The Celestron 70 telescope, specifically the Celestron Astromaster 70, is a popular choice among amateur astronomers and casual stargazers. This telescope is known for its user-friendly design and impressive optical performance, making it suitable for both beginners and those with some experience in astronomy.

One of the most notable features of the Celestron 70 is its 70mm aperture. This size provides ample light-gathering capability, allowing for the observation of celestial objects such as planets, star clusters, and even some of the brighter deep-sky objects. The optical system consists of a refractor design with fully coated glass optics, ensuring bright and clear images.

The Celestron 70 also incorporates a sturdy mount. The manual Altazimuth mount is intuitive and easy to use, making it simple for users to locate and track astronomical objects in the night sky. It is often equipped with slow-motion controls that help with precision tracking. The lightweight design of the telescope allows for easy portability, making it ideal for viewing sessions in various locations, whether in your backyard or at a remote dark-sky site.

Another key technology in the Celestron 70 is its erect image optics, which produce images that are oriented correctly, making it suitable for both astronomical and terrestrial viewing. Users can easily switch between observing the craters of the Moon, the rings of Saturn, or scenic landscapes during the day.

In addition, the Celestron 70 comes with several useful accessories. It typically includes a finderscope that assists users in locating celestial objects, as well as a collection of interchangeable eyepieces to enhance the viewing experience. The included software often provides a great introduction to astronomy, helping users learn about the various constellations and celestial bodies they can observe.

Overall, the Celestron 70 telescope combines affordability with quality, making it an excellent choice for newcomers to astronomy or anyone looking for a reliable scope for casual observation. With its impressive features, robust design, and user-friendly functionality, it caters to the growing interest in stargazing, inviting users of all ages to explore the wonders of the universe. Whether a clear night brings a chance to observe the intricacies of the Moon's surface or distant stars, the Celestron 70 is poised to provide an enjoyable viewing experience.
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