A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused. Some telescopes, known as refractors, use lenses. Other telescopes, known as reflectors, use mirrors. Developed in the early 1600s, the refractor is the oldest telescope design. It derives its name from the method it uses to focus incoming light rays. The refractor uses a lens to bend or refract incoming light rays, hence the name (see Figure 4-1). Early designs used single element lenses. However, the single lens acts like a prism and breaks light down into the colors of the rainbow, a phenomenon known as chromatic aberration. To get around this problem, a two-element lens, known as an achromat, was introduced. Each element has a different index of refraction allowing two different wavelengths of light to be focused at the same point. Most two-element lenses, usually made of crown and flint glasses, are corrected for red and green light. Blue light may still be focused at a slightly different point.

Figure 4-1

A cutaway view of the light path of the Refractor optical design

Image Orientation

It should be noted that the image orientation will change depending on the viewing configuration. When using the star diagonal, the image is right-side-up, but reversed from left-to-right. If inserting the eyepiece into the accessory adapter (i.e., without the star diagonal), the image is inverted (upside down and reversed from left-to-right). This holds true for the 9x50 finder as well as the telescope. For correct orientation through the telescope, which is important primarily for terrestrial observing, use the optional 45° erect image diagonal 1-1/4" (#94112-A).

Actual image orientation as seen

with the unaided eye

Reversed from left to right, as viewed with a Star Diagonal

Inverted image, as viewed with the eyepiece directly in telescope

Figure 4-2

29

Page 29
Image 29
Celestron C100ED-R, C80ED-R manual Image Orientation

C100ED-R, C80ED-R specifications

Celestron, a renowned name in the field of astronomy, has built a reputation for producing high-quality telescopes that are accessible to both amateur and professional astronomers alike. Among their impressive lineup are the Celestron C100ED-R and C80ED-R telescopes, both of which are crafted to enhance the observational experience through advanced optics and user-friendly features.

The Celestron C100ED-R, a 100mm refractor telescope, stands out for its premium extra-low dispersion (ED) glass, which delivers exceptional color correction and sharpness. This ED technology minimizes chromatic aberration, ensuring clearer and more colorful celestial images. The telescope boasts a focal length of 900mm, resulting in a focal ratio of f/9. This combination allows for high magnification capabilities while maintaining a wide field of view, perfect for observing both planetary details and deep-sky objects. The robust, yet lightweight design of the C100ED-R makes it highly portable, allowing for convenient stargazing sessions.

On the other hand, the C80ED-R is a 80mm refractor telescope that combines portability with performance. With its 600mm focal length and f/7.5 focal ratio, the C80ED-R is ideal for wide-field observations, making it easy to explore star clusters and large nebulae. Like its larger counterpart, the C80ED-R features ED glass, which prevents color distortion, allowing for clear and crisp images. The compact design is perfect for those who wish to travel or set up in tight spaces, ensuring that astronomy remains accessible.

Both telescopes are equipped with high-quality multi-coated optics that enhance light transmission, resulting in brighter images. Celestron's user-friendly mounting systems allow for smooth tracking of celestial objects, making it easier to follow objects as they move across the night sky. Additionally, these telescopes come with a variety of accessories, including premium eyepieces that enhance the viewing experience, and sturdy tripods that provide stable support during observations.

In summary, both the Celestron C100ED-R and C80ED-R offer exceptional features that cater to a variety of observing needs. With advanced ED optics, high-quality construction, and portability, they are ideal choices for aspiring astronomers looking to explore the wonders of the universe. Whether you're interested in planetary observation or deep-sky exploration, Celestron's C100ED-R and C80ED-R will not disappoint.