David White L6-20, Руководство пользователя

Страница: 6 / 16

-6-
GENERAL DESCRIPTION
Telescope
The telescope provides a sharp image
magnified 22 times. This means the
object sighted appears 22 times closer
than it would with the naked eye.
The telescope features a built-in
sunshade which protects the objective
lens 1 and reduces glare.
To focus on an object, sight through
the eyepiece 2 and turn the focusing
knobs 3 with either right or left hand.
Cross hairs are in constant focus. All
focusing is internal. The telescope does
not move outward or inward as objects
are focused. David White Meridian
instruments use the smooth precision of a
rack and pinion mechanism for focusing.
Focus range is from four feet to
infinity. For closer focus, turn the knob
clockwise. For farther focusing, turn
counterclockwise.
Leveling Vial
The instrument leveling vial 4 is protected
by a strong, die-cast casing, and is
graduated to facilitate centering the
bubble.
Horizontal Circle
The horizontal circle 5 can be rotated for
easy angle setting and reading and is
divided in quadrants (0-90°). The circle is
marked by degrees and numbered every
10 degrees.
The horizontal vernier
6 permits dividing
whole degrees into fractions of 1/4°
(15 minutes). Approximate horizontal
sightings are held firmly in place by means
of a clamp 7 . Then, precise horizontal
settings can be made with the tangent
8 . The clamp must be hand tightened in
order for the tangent to function.
Vertical Arc (LT6-900 Only)
The LT6-900 is a combination instrument.
Its telescope moves up and down 45
degrees, and rotates 360 degrees, to
measure vertical and horizontal angles.
The telescope lock lever
9 must be in a
closed position when the instrument is to
be used as a level; open when used as a
transit for vertical sightings. It is shown in
the open position.
The vertical arc
10 is divided in degrees
and numbered every 10 degrees up to 45
degrees, for both upward and downward
angles, and has an adjustable index
pointer 11 .
The vertical clamp 12 holds the telescope
at a vertical angle. Fine vertical settings
can be made with the vertical tangent
13 . The vertical clamp must be hand
tightened before the tangent will function.
Leveling Screws
Both instruments have three leveling
screws 14 for leveling the instrument. The
instrument is mounted to the tripod by
screwing the tripod stud into the 5/8-11
threaded base 15 .