Solar Observing Hints; Observing Deep Sky Objects; Seeing Conditions; Transparency - Celestron 127SLT User Manual

Celestron 127slt: user guide
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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 SLT models, be sure to select solar tracking rate.
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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.
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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.
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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.
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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.
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