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The best time to observe the Sun is in the early morning or late afternoon when the air is cooler.
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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 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.
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.
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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 some where between these two
extremes.
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Figure 7-1
36
Conditions include
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