"Seeing" Conditions; Transparency; Sky Illumination - Celestron STAR HOPPER Instruction Manual

Although the Ring Nebula lies between two "naked eye" stars, it may take a little time to locate because it isn't
visible in a finderscope. Note that the scale for this star chart is different from that of the chart on the previous page,
which shows several constellations, including Pegasus, Triangulum and Andromeda.

"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 affect they have on
observing will help you get the most out of your telescope.

Transparency

Transparency refers to the clarity of the atmosphere and is affected by clouds, moisture, dust and other airborne
particles. Thick cumulus clouds are completely opaque, while cirrus clouds can be thin, allowing light from the
brightest stars through. Hazy skies absorb more light than clear skies, making fainter objects hard to see and
reducing contrast on brighter objects. Dust particles and gases 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 effect transparency.
While not a problem when viewing 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. Light Pollution Reduction (LPR) filters
enhance deep-sky viewing from light polluted areas by blocking unwanted light, while transmitting light from certain
deep-sky objects. Planets and stars can still be observed from light polluted areas or when the moon is out.
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