Terminology; Assembly - Orion 9931 Instruction Manual

2. terminology

Altitude Bearings The two round plastic protrusions on
opposite sides of the optical tube, which rest in the cradle of
the Dobsonian base. They allow the telescope to be pivoted
up or down (altitude).
Altitude Bearing Pads The pads of material on the Dobsonian
cradle where the optical tube side (altitude) bearings rest.
Azimuth Pads The white Teflon pads between the two base
plates, which allow the telescope to be moved side to side
(azimuth).
Azimuth Pivot Bolt The bolt through the center of the two
base plates, which serves as a pivot point for azimuthal rotation.
Collimation Alignment of the optical elements of an instru-
ment. Proper collimation is necessary to achieve peak optical
performance.
Ground Baseplate On the Dobsonian base, the round board
closest to the ground. It often has "feet" on the underside and
three azimuth bearing pads on the perimeter of its upper surface.
Dobsonian Mount A type of simple, cabinet-style altazimuth
mount for a Newtonian reflector, invented by John Dobson of
the San Francisco Sidewalk Astronomers club.
Eyepiece A lens-containing barrel that magnifies the image
formed by the telescope and allows your eye to focus on it.
Eyepieces of different focal lengths will produce different
magnification factors.
Finder Scope A small, low-power refracting telescope, usu-
ally with crosshairs, mounted on the optical tube of the main
telescope to aid in pointing the telescope. Its wide field of view
facilitates the location of target objects. When properly
aligned with the main telescope, an object centered in the
finder scope will also be centered in the main telescope's
much narrower field of view.
Optical Tube The main body of the telescope, which houses
the optics.
Primary Mirror The large, concave mirror located at the back
end of the optical tube. It reflects incoming light to the second-
ary mirror near the front of the tube.
Primary Mirror Cell The mechanical holder for the primary
mirror. It features alignment-adjusting bolts (usually three)
that allow exact positioning of the tilt of the primary mirror.
Rack-and-Pinion Focuser A type of mechanical holder for
the eyepiece that enables the eyepiece to be moved in and out
to achieve sharp focus of the viewed image. It moves through
the interaction of a sawtoothed "rack" on the focuser drawtube
with a meshing "pinion" gear that is rotated with one's fingers.
Secondary Mirror The small, elliptically shaped, flat mirror
located inside the optical tube beneath the focuser. Its func-
tion is to divert the light transmitted from the primary mirror
sideways into the focusing tube.
Secondary Mirror Cell The mechanical holder for the sec-
ondary mirror; usually a single stalk or an adjustable multivane
"spider."
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Top Baseplate On the Dobsonian base, the uppermost of the
two round boards, which rests atop the ground baseplate. It
supports the vertical struts of the telescope tube cradle. The
top baseplate rotates on the ground baseplate, allowing the
telescope to be moved in the azimuthal direction.

3. assembly

unpacking Your new telescope
The telescope will arrive in two boxes, one containing the
telescope tube and optics, the other containing the unas-
sembled Dobsonian base and hardware. Exercise care when
unpacking the boxes. We recommend keeping the original
shipping containers; in the event that the telescope needs to
be shipped to another location or returned to Orion for war-
ranty repair, having the proper shipping containers will help
ensure that your telescope will survive the journey intact.
assembly of the Dobsonian Base
Before the telescope can be used, the base must be assem-
bled. This only has to be done once, unless you disassemble
the base for long term storage. The assembly process takes
about 15 minutes and requires only a Phillips screwdriver, the
large and small Allen wrenches provided, and two 1/2"
wrenches, or a combination of a wrench and pliers.
Note: When tightening screws, tighten them by hand until
firm, but be careful not to strip the holes by over-tightening. If
you use an electric screwdriver, do final tightening by hand.
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Figure 1.
(refer to Figure 1)
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