Celestron NexStar 5i Manuel d'instructions télécharger pdf (Page 32)

Never project an image of the Sun through the telescope. Because of the folded optical design, tremendous

heat build-up will result inside the optical tube. This can damage the telescope and/or any accessories

attached to the telescope.

For safe solar viewing, use a solar filter that reduces the intensity of the Sun's light, making it safe to view.

With a filter you can see sunspots as they move across the solar disk and faculae, which are bright patches

seen near the Sun's edge.

Solar Observing Hints

• The best time to observe the Sun is in the early morning or late afternoon when the air is cooler.

• To center the Sun without looking into the eyepiece, watch the shadow of the telescope tube until it

forms a circular shadow.

• To ensure accurate tracking, be sure to select the solar tracking rate.

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.

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 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.

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 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.

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Celestron NexStar 5i Manuel d'instructions Page 32