Focal Length of Telescope (mm)

Magnification = 

Focal Length of Eyepiece (mm)

Let’s say, for example, you are using the 20mm eyepiece. To determine the magnification you simply divide the focal length of your telescope (the C8-N for example has a focal length of 1000mm) by the focal length of the eyepiece, 20mm. Dividing 1000 by 20 yields a magnification of 50 power.

Although the power is variable, each instrument under average skies has a limit to the highest useful magnification. The general rule is that 60 power can be used for every inch of aperture. For example, the C8-N is 8 inches in diameter. Multiplying 8 by 60 gives a maximum useful magnification of 480 power. Although this is the maximum useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture which is 160 to 280 times for the C8-N telescope.

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 50°. Divide the 50° by the magnification, which is 50 power. This yields an actual field of 1°, or 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 1° by 52.5. This produces a linear field width of 52.5 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).

General Observing Hints

When working with any optical instrument, there are a few things to remember to ensure you get the best possible image.

•Never look through window glass. Glass found in household windows is optically imperfect, and as a result, may vary in thickness from one part of a window to the next. This inconsistency can and will affect the ability to focus your telescope. In most cases you will not be able to achieve a truly sharp image, while in some cases, you may actually see a double image.

•Never look across or over objects that are producing heat waves. This includes asphalt parking lots on hot summer days or building rooftops.

•Hazy skies, fog, and mist can also make it difficult to focus when viewing terrestrially. The amount of detail seen under these conditions is greatly reduced. Also, when photographing under these conditions, the processed film may come out a little grainier than normal with lower contrast and underexposed.

•If you wear corrective lenses (specifically glasses), you may want to remove them when observing with an eyepiece attached to the telescope. When using a camera, however, you should always wear corrective lenses to ensure the sharpest possible focus. If you have astigmatism, corrective lenses must be worn at all times.

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Celestron C8-NGT, C10-N manual Determining Field of View, General Observing Hints
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C10-N, C8-NGT, C8-N specifications

The Celestron C8-NGT, C8-N, and C10-N telescopes represent a range of superior astronomical instruments that cater to both novice and experienced astronomers alike. Among these, the C8-NGT combines the advanced features of a computerized telescope with the simplicity of a Newtonian design. Its 8-inch aperture allows for impressive light-gathering capability, making it ideal for observing distant galaxies, star clusters, and nebulae. The GoTo mount enhances usability, enabling users to locate celestial objects effortlessly with the push of a button.

The C8-N, also featuring an 8-inch aperture, stands out with its open tube design that provides maximum airflow and minimizes thermal issues, ensuring optimal performance. The scope is designed with user-friendly adjustments and a sturdy equatorial mount, allowing for smooth tracking of celestial objects. Its high-quality optics provide sharp images and incredible clarity, making it suitable for both planetary and deep-sky observations.

On the other hand, the C10-N is the largest in this lineup, boasting a 10-inch aperture that dramatically enhances its light-gathering ability. This larger size makes the C10-N a powerhouse for serious astronomers looking to explore fainter objects and intricate details within astronomical features. Like the C8-N, it employs a Newtonian reflector design, allowing for a compact and manageable profile, while still providing stunning visuals across a range of celestial bodies.

All three telescopes incorporate Celestron's commitment to creating durable, robust, and user-friendly systems. They utilize premium quality glass and optics, which are coated to improve light transmission and provide high-contrast images. Additionally, they are designed with ease of assembly and portability in mind, catering to astronomers who enjoy observing in various locations.

The Celestron C8-NGT, C8-N, and C10-N serve as excellent options for anyone looking to deepen their astronomical pursuits, offering a blend of advanced technology, high-quality optical performance, and user-friendly features. Whether you're a beginner eager to peer into the wonders of the universe or an experienced observer at the peak of your skills, these telescopes offer a remarkable means to expand your cosmic horizons. With precision engineering and thoughtful design, Celestron continues to be a trusted name in the world of astronomy.
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