Celestron 11091 Buku Petunjuk - Halaman 9

Jelajahi secara online atau unduh pdf Buku Petunjuk untuk Teleskop Celestron 11091. Celestron 11091 20 halaman. Telescope and equatorial mount

Focusing

Focusing the G-5 telescope:

The G-5 telescope has a focusing knob located on the rear cell of the optical tube to the right of the star

diagonal and eyepiece. Turn the focusing knob until the image is sharp. If the knob will not turn, the

primary mirror has reached the end of its travel on the focusing mechanism. Turn the knob in the opposite

direction until the image is sharp. Once an image is in focus, turn the knob clockwise to focus on a closer

object and counterclockwise for a more distant object. For astronomical viewing, out-of-focus star images

are very diffuse making them difficult, if not impossible, to see. For best results, your first astronomical

target should be a bright object (like the Moon) so that the image is visible even when out of focus.

Focusing the G-3 telescope:

To focus the G-3 telescope turn the focuser ring (see figure 1) on the optical tube until the image is sharp.

For objects closer than the one you are currently observing, turn the focusing ring clockwise and for objects

further away, turn counterclockwise. The G-3 has a tremendous amount of focus travel to allow for critical,

sharp focusing. For astronomical viewing, out-of-focus star images are very diffuse making them difficult, if

not impossible, to see. For best results, your first astronomical target should be a bright object (like the

Moon) so that the image is visible even when out of focus.

Calculating Magnification

The magnification (or power) of a telescope is variable depending upon the focal length of the eyepiece

being used along with the focal length of the telescope.

To calculate the magnification we use the following formula:

where FL(telescope) is the focal length of the telescope and FL(eyepiece) is the focal length of the

eyepiece. For example, if the focal length of the G-3 telescope is 1000mm and you use a 25mm

eyepiece your magnification is 1000/25 = 40x.

There are numerous optional eyepieces that are available to expand your range of magnification. There

are various types of eyepieces of varying quality to choose from.

The Celestial - Coordinate System

The celestial-coordinate system is an imaginary projection of the Earth's geographical coordinate system

onto the celestial sphere which seems to turn overhead at night. This celestial grid is complete with equator,

latitudes, longitudes and poles.

The Earth is in constant motion as it rotates on its axis. Actually the celestial-coordinate system is being

displaced very slowly with respect to the stars. This is called precession and is caused by gravitational

influences from the Sun, Moon and other celestial bodies.

Telescope Basics

FL telescope

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Magnification

FL eyepiece

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