Up to this point, this manual covered the assembly and basic operation of your telescope. However, to understand your telescope more thoroughly, you need to know a little about the night sky. This section deals with observational astronomy in general and includes information on the night sky and polar alignment.

The Celestial Coordinate System

To help find objects in the sky, astronomers use a celestial coordinate system that is similar to our geographical coordinate system here on Earth. The celestial coordinate system has poles, lines of longitude and latitude, and an equator. For the most part, these remain fixed against the background stars.

The celestial equator runs 360 degrees around the Earth and separates the northern celestial hemisphere from the southern. Like the Earth's equator, it bears a reading of zero degrees. On Earth this would be latitude. However, in the sky this is referred to as declination, or DEC for short. Lines of declination are named for their angular distance above and below the celestial equator. The lines are broken down into degrees, minutes of arc, and seconds of arc. Declination readings south of the equator carry a minus sign (-) in front of the coordinate and those north of the celestial equator are either blank (i.e., no designation) or preceded by a plus sign (+).

The celestial equivalent of longitude is called Right Ascension, or R.A. for short. Like the Earth's lines of longitude, they run from pole to pole and are evenly spaced 15 degrees apart. Although the longitude lines are separated by an angular distance, they are also a measure of time. Each line of longitude is one hour apart from the next. Since the Earth rotates once every 24 hours, there are 24 lines total. As a result, the R.A. coordinates are marked off in units of time. It begins with an arbitrary point in the constellation of Pisces designated as 0 hours, 0 minutes, 0 seconds. All other points are designated by how far (i.e., how long) they lag behind this coordinate after it passes overhead moving toward the west.

Figure 5-1

The celestial sphere seen from the outside showing R.A. and DEC.

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Celestron C8-S, C9-S, C5-S instruction manual Celestial Coordinate System
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C5-S, C9-S, C8-S specifications

Celestron, a leader in the field of amateur and professional astronomy, offers a range of telescopes ideal for both novices and experienced stargazers. Among their most celebrated models are the C8-S, C5-S, and C9.25-S, each designed with unique features and technologies that enhance the observational experience.

The Celestron C8-S is an iconic telescope known for its 8-inch aperture. This Schmidt-Cassegrain design combines a compact form factor with a powerful light-gathering capability, making it perfect for deep-sky observing. Its optical tube has a focal length of 2032mm, providing an excellent balance of wide field viewing and high magnification. The C8-S features Celestron's StarBright XLT optical coating, enhancing light transmission and contrast, ensuring that even faint objects are visible. With compatibility for various accessories and a sturdy mount, the C8-S stands as a versatile option for different observing styles.

Moving to the C5-S, this model boasts a 5-inch aperture while maintains a compact and portable design. It is particularly popular among travelers and casual astronomers who value convenience without compromising on quality. The C5-S also employs the Schmidt-Cassegrain design, providing sharp images and improved color correction. With its shorter focal length of 1250mm, the C5-S excels in both planetary and deep-sky observation. The telescope's lightweight build makes it easy to transport, while the integrated optical systems ensure a clear view of celestial objects.

The C9.25-S represents a step up in performance, featuring a 9.25-inch aperture that captures more light than its smaller counterparts. This telescope offers a versatile focal length of 2350mm, allowing for impressive high-power planetary views, as well as detailed observations of deep-sky objects. The C9.25-S utilizes a unique StarBright XLT coating and features advanced optics that minimize optical distortion, resulting in sharp, high-contrast images. It is equipped with a sturdy mount that ensures stability during extended observation sessions.

All three models are compatible with Celestron's advanced computer-driven mount systems, allowing for effortless tracking and alignment. With built-in features such as GoTo technology, users can easily locate thousands of celestial objects with the touch of a button. This combination of advanced optics, portability, and user-friendly technology makes the Celestron C8-S, C5-S, and C9.25-S excellent choices for anyone looking to explore the cosmos more deeply. Whether for casual stargazing or serious astronomical study, these telescopes deliver exceptional performance to meet a variety of needs.
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