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 25mm eyepiece. The 25mm eyepiece has an apparent field of view of 56°. Divide the 56° by the magnification, which is 40 power. This yields an actual field of view of 1.4°.

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 1.4° by 52.5. This produces a linear field width of 73.5 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.

80GTL specifications

The Celestron 80GTL is a powerful and compact telescope designed for both amateur astronomers and experienced stargazers. It combines modern technology with user-friendly features, making it an excellent choice for those looking to explore the night sky. With its 80mm aperture, the 80GTL captures enough light to reveal a variety of celestial objects, from the moon’s craters to distant galaxies.

One of the standout characteristics of the Celestron 80GTL is its innovative Altazimuth mount. This mount provides smooth and precise movements in both horizontal and vertical directions, allowing users to easily track celestial objects as they move across the sky. The setup is quick and straightforward, making it ideal for beginners who may be intimidated by more complex mounts.

The telescope is equipped with Celestron’s StarScope system, which includes a computer-controlled GoTo mount. This feature allows users to automatically locate and track over 40,000 celestial objects with the push of a button. The included hand controller is intuitive and easy to navigate, giving users instant access to stars, planets, and deep-sky objects. This technology not only enhances the viewing experience but also helps novice astronomers learn about the universe with guided tours through the night sky.

Another notable feature of the Celestron 80GTL is its sturdy construction and lightweight design. Made from high-quality materials, it boasts durability while remaining portable for easy transport. Weighing just under 10 pounds, this telescope can be taken on camping trips or excursions, allowing users to enjoy astronomy in various locations.

Additionally, users will appreciate the 80GTL’s fully coated glass optics which provide excellent image quality and contrast. The included 25mm and 10mm eyepieces offer different magnifications, catering to diverse viewing preferences. Whether observing the rings of Saturn or the detail of lunar landscapes, the 80GTL promises clear and sharp images.

In summary, the Celestron 80GTL is a highly capable telescope, combining an accessible design with advanced technologies. Its user-friendly GoTo mount, quality optics, and lightweight build make it an exceptional option for anyone wishing to delve into the wonders of the cosmos, ensuring both enjoyment and education in the field of astronomy.

Celestron 80GTL manual Determining Field of View, General Observing Hints

Models: 80GTL