Celestron 80GTL manual Solar Observing Hints, Observing Deep Sky Objects, Terrestrial Land Viewing

•Sunspots: Dark regions of the sun's photosphere which are cooler than the surrounding area. Sunspots are usually

seen to consist of two parts: the inner darker core, the umbra, and the surrounding less dark region, the penumbra.

•Granulation: Small convection cells in the photosphere that appear as "rice grain" markings.

•Faculae: Large patches of bright material probably due to elevated clouds of luminous gas seen in the vicinity of sunspots.

•Limb Darkening: An observed darkening near the limb of the sun's surface compared to its brighter center due to the amount of atmospheric layers penetrated when viewing the sun's limb.

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 on GT models, be sure to select solar tracking rate.

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.

Terrestrial (Land) Viewing

Your NexStar 80GTL also makes an excellent daytime spotting scope. For daytime viewing, the 90˚ erect image diagonal must be inserted into the telescope's focuser. For correct viewing of land objects make sure the eyepiece is pointing straight up out of the diagonal. Rotating the eyepiece and diagonal to either size will cause the image to also rotate in the field of view of the eyepiece.

Terrestrial (Land) Viewing Hints

To save land objects into your hand control’s database as User Defined Objects, first complete the Quick Alignment procedure, this will bypass the normal two star alignment needed for nighttime viewing.

Since daytime land objects usually remain stationary, remember to turn off the telescopes tracking.

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

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