Observing Deep Sky Objects

Deep-sky objects are simply those objects outside the boundaries of our solar system. They include star clusters, planetary nebulae, diffuse nebulae, double stars and other galaxies outside our own Milky Way. Most deep-sky objects have a large angular size. Therefore, low-to-moderate power is all you need to see them. Visually, they are too faint to reveal any of the color seen in long exposure photographs. Instead, they appear black and white. And, because of their low surface brightness, they should be observed from a dark-sky location. Light pollution around large urban areas washes out most nebulae making them difficult, if not impossible, to observe. Light Pollution Reduction filters help reduce the background sky brightness, thus increasing contrast.

Seeing Conditions

Viewing conditions affect what you can see through your telescope during an observing session. Conditions include transparency, sky illumination, and seeing. Understanding viewing conditions and the effect they have on observing will help you get the most out of your telescope.

Transparency

Transparency is the clarity of the atmosphere which is affected by clouds, moisture, and other airborne particles. Thick cumulus clouds are completely opaque while cirrus can be thin, allowing the light from the brightest stars through. Hazy skies absorb more light than clear skies making fainter objects harder to see and reducing contrast on brighter objects. Aerosols ejected into the upper atmosphere from volcanic eruptions also affect transparency. Ideal conditions are when the night sky is inky black.

Sky Illumination

General sky brightening caused by the Moon, aurorae, natural airglow, and light pollution greatly affect transparency. While not a problem for the brighter stars and planets, bright skies reduce the contrast of extended nebulae making them difficult, if not impossible to see. To maximize your observing, limit deep sky viewing to moonless nights far from the light polluted skies found around major urban areas. LPR filters enhance deep sky viewing from light polluted areas by blocking unwanted light while transmitting light from certain deep sky objects. You can, on the other hand, observe planets and stars from light polluted areas or when the Moon is out.

Seeing

Seeing conditions refers to the stability of the atmosphere and directly affects the amount of fine detail seen in extended objects. The air in our atmosphere acts as a lens which bends and distorts incoming light rays. The amount of bending depends on air density. Varying temperature layers have different densities and, therefore, bend light differently. Light rays from the same object arrive slightly displaced creating an imperfect or smeared image. These atmospheric disturbances vary from time-to-time and place-to-place. The size of the air parcels compared to your aperture determines the "seeing" quality. Under good seeing conditions, fine detail is visible on the brighter planets like Jupiter and Mars, and stars are pinpoint images. Under poor seeing conditions, images are blurred and stars appear as blobs.

The conditions described here apply to both visual and photographic observations.

Figure 5-3

Seeing conditions directly affect image quality. These drawings represent a point source (i.e., star) under bad seeing conditions (left) to excellent conditions (right). Most often, seeing conditions produce images that lie somewhere between these two extremes.

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Celestron Scope 90 manual Observing Deep Sky Objects, Seeing Conditions
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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.
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