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3.Be sure the Mount is placed on a relatively level surface to allow proper operation. The feet should be in firm contact and not wobble. If you are in an area with particularly rough or soft ground, it may be helpful to place the Mount on a thick piece of plywood.
4.Part of the fun of using a Dobsonian type of telescope is the challenge of hunting for objects in the night sky. Invest is some simple star charts and books that tell you how to locate objects using a technique called “star hopping.” Once you begin learning the star patterns and constellations, you’re well on you way to finding many amazing sights.
G. MAGNIFYING POWER
The operating magnification of the telescope is a function of two distinct optical characteristics: the focal length of the telescope and the focal length of the eyepiece in use. For example, using the 25mm eyepiece with the Starfinder Dobsonian 16 yields 73X, computed as follows:
1828mm (focal length of the telescope)
___________________________________ = 73X
25mm (focal length of the eyepiece)
The type of eyepiece, whether Modified Achromatic, Plössl, or Super Plössl, has no effect on magnification, but does have a bearing on such optical characteristics as field of view, flatness of field, and color correction.
Maximum practical magnification is about 50X per inch of aperture. Generally, however, lower powers will produce higher image resolution. When unsteady air conditions prevail (as witnessed by rapid “twinkling” of the stars), extremely high powers result in “empty” magnification, where the object detail observed is actually diminished by the excessive power.
When beginning observations on a particular object, start with a low power eyepiece; get the object well- centered in the field of view and sharply focused. Then try the next step up in magnification. If the image starts to become fuzzy as you work up into higher magnifications, then back down to a lower power: the atmospheric steadiness is not sufficient to support high powers at the time you are observing. Keep in mind that a bright, clearly resolved, but smaller, image will show far more detail than a dimmer, poorly resolved, larger image.
Because of certain characteristics of the human eye (in particular, eye pupil diameter) and because of optical considerations inherent in the design of the telescope, there exist minimum practical power levels also. Generally speaking the lowest usable power is approximately 4X per inch of telescope aperture.
H. SEEING CONDITIONS
Even in normal city conditions, with all of the related air and light pollution, there are many interesting celestial objects to observe. But, to be sure, there is no substitute for the clear, dark, steady skies generally found only away from urban environments, or on mountaintops: objects previously viewed only in the city take on added detail or are seen in wider extension, or even become visible at all for the first time.
The amateur astronomer is faced typically with two broadly defined problems when viewing astronomical objects through the Earth’s atmosphere: first is the clarity, or transparency, of the air, and secondly the steadiness of the air. This latter characteristic is often referred to as the quality of “seeing.” Amateur astronomers talk almost constantly about the “seeing conditions,” since, perhaps ironically, even the clearest, darkest skies may be almost worthless for serious observations if the air is not steady. This steadiness of the atmosphere is most readily gauged by observing the “twinkling” of the stars: rapid twinkling implies air motion in the Earth’s atmosphere, and under these conditions, resolution of fine detail (on the surface of Jupiter, for instance) will generally be limited. When the air is steady, stars appear to the naked eye as untwinkling points of unchanging brightness, and it is in such a situation that the full potential of the telescope may be realized: higher powers may be used to advantage, closer double stars resolved as distinct points, and fine detail observed on the Moon and planets.
