Determining Field of View

Magnification = ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

Focal Length of Eyepiece (mm)

Let’s say, for example, you are using the 10mm eyepiece that came with your telescope. To determine the magnification you simply divide the focal length of your telescope (the SkyScout Scope for this example has a focal length of 660mm) by the focal length of the eyepiece, 10mm. Dividing 660 by 10 yields a magnification of 66 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 SkyScout Scope is 3.5 inches (90mm) in diameter. Multiplying 3.5 by 60 gives a maximum useful magnification of over 212 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 70 to 123 times for the SkyScout Scope. You can determine the magnification for your telescope the same way.

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 10mm eyepiece that is supplied standard with the SkyScout Scope. The 10mm eyepiece has an apparent field of view of 50°. Divide the 50° by the magnification, which is 66 power. This yields an actual field of .75°.

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 of .75° by 52.5. This produces a linear field width of 39 feet at a distance of one thousand yards.

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.

•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.

Scope 90 specifications

The Celestron Scope 90 is a powerful refractor telescope that combines portability, performance, and user-friendly features, making it an excellent choice for both novice and experienced astronomers. This telescope is designed to provide impressive views of celestial objects, from the craters of the Moon to distant planets and star clusters.

One of the standout features of the Celestron Scope 90 is its 90mm aperture, which allows for significant light-gathering capacity. This means that users can enjoy brighter and clearer images of various astronomical phenomena. The telescope employs high-quality optics with fully coated glass lenses that enhance image contrast and clarity, ensuring a pleasurable viewing experience.

Another notable characteristic of the Celestron Scope 90 is its compact and lightweight design. Weighing in at just a few pounds, it is easily portable, making it ideal for stargazing on the go or for backyard observing. The included adjustable aluminum tripod offers stability without adding excessive weight, contributing to the telescope’s ease of transport.

The telescope features a simple yet effective altazimuth mount, making it straightforward to point at objects in the sky. The mount allows for smooth movement in both horizontal and vertical directions, giving users the freedom to track celestial objects with ease. Additionally, Celestron includes a StarPointer finderscope that helps users locate their desired targets quickly and efficiently.

Furthermore, the Celestron Scope 90 is equipped with two eyepieces, offering different magnification levels to enhance viewing versatility. This allows users to switch between low and high magnification for various astronomical objects. Whether observing the rings of Saturn or the details of a distant galaxy, the Celestron Scope 90 provides a rich viewing experience.

Celestron has also integrated advanced technologies into the Scope 90, including a robust build quality that enhances durability. The telescope's design is made to endure various weather conditions, making it suitable for field use. It's also compatible with optional accessories, such as solar filters and additional eyepieces, allowing users to expand their astronomical observations.

In summary, the Celestron Scope 90 stands out as a compact, powerful, and user-friendly telescope. With its impressive optics, portability, and advanced features, it caters to a wide range of astronomical interests, making it a reliable companion for anyone eager to explore the wonders of the night sky. Whether you're just starting your stargazing journey or are an experienced astronomer, this telescope offers the capabilities you need for an enjoyable and rewarding experience.