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Fig. 8: Viewfinder.
(1) Viewfinder Eyepiece; (2) Rear Alignment
Screws; (3) Mounting Bracket; (4) Front Alignment Screws; (5) Focus
Lock Ring; (6) Objective Lens Cell.
FIRST OBSERVATIONS
Remove the dust cover from the objective lens by gently twisting
the cover and pulling It away from the objective lens.
Telescope Controls
An important array of controls facilitates operation of the Model
102ACHR/500 telescope. It is best to become familiar with all
of these controls before attempting observations through the
telescope.
Focus Knobs (7), Fig. 6:
Turning these knobs moves the
eyepiece closer to or farther away from the objective lens,
thereby changing the focus. The telescope can be focused on
objects from a distance of about 50 feet to infinity.
Focus Lock Knob (3), Fig. 6: The focus lock knob is designed
to prevent the focuser drawtube (6), Fig. 6, from moving when
heavy accessories (e.g., a camera body) are attached to the
focuser assembly. For normal observing, with an eyepiece and
diagonal mirror, it is not necessary to utilize the lock knob.
Dec Lock Lever (1), Fig. 7:
Locking and unlocking the
Declination movement of the optical tube is accomplished by
moving the Dec lock lever clockwise until it stops for the fully
locked
position,
or
by
moving
the
Dec
lock
lever
counterclockwise to the fully unlocked position.
Dec Slow-Motion Control (4), Fig. 7: With the Dec lock lever in
the fully locked position, the Dec Slow-Motion Control may be
used for fine motions of the telescope in Declination.
(The
meaning of ''Dec," or Declination, is explained later in the
manual.)
R.A. Lock Lever (3), Fig. 7:
Locking and unlocking the Right
Ascension movement is accomplished by rotating the R.A. lock
lever clockwise until it stops for the fully locked position and
counterclockwise for the fully unlocked position.
R.A. Slow-Motion Control (2), Fig. 7: With the R.A. lock lever
fully locked, the R.A. Slow-Motion Control permits manual slow-
motion of the telescope in Right Ascension.
(The meaning of
"R.A.," or Right Ascension, is explained later in the manual.)
After becoming familiar with the telescope's controls, make your
first observations of a simple land object — a telephone pole or
building, perhaps, several hundred yards in the distance. Keep
in mind that the viewfinder has not been aligned, so it will be
necessary to sight along the optical tube to "aim" the telescope
at the object. With the PL 25mm eyepiece in place, unlock the
R.A, and Dec lock levers. The telescope now turns freely on
both axes, permitting the location of objects in the telescope.
With an object roughly centered in the telescopic field, as
viewed through the eyepiece, retighten the R.A. and Dec lock
levers. While looking through the eyepiece, turn the focus knob
clockwise or counterclockwise until the object is in focus.
Note: With the eyepiece inserted directly into the rear cell of the
telescope, without using the diagonal prism, the image through
the eyepiece will be inverted and reversed left-for-right.
The
inverted image is a result of the optical structure of the telescope
and is normal for astronomical telescopes. If the diagonal prism
is inserted into the telescope first, then the eyepiece, the image
appears right-side-up, but still reversed left-for-right.
Once the selected object is in focus, with the R.A. lock lever and
Dec lock lever LOCKED, use the R.A. Slow-Motion Control and
the Dec Slow-Motion Control to center the object in the field of
view,
THE VIEWFINDER
The Model 102ACHR/500 telescope, as with almost all
astronomical telescopes, presents a fairly narrow field of view to
the observer. As a result, it is sometimes difficult to locate and
center objects in the telescope. The viewfinder, by contrast, is
a low-power, wide-field sighting scope with crosshairs that
enable the easy centering of objects in the main telescope's
field of view. Standard equipment with the Model 102ACHR/500
telescope is a viewfinder of 6-power and 30mm aperture, called
a "6 x 30mm viewfinder.".
1. Focusing the Viewfinder
The viewfinder has been factory prefocused to objects located
at infinity. Individual eye variations, however, may require that
the viewfinder be refocused to your eye. Looking through the
viewfinder, point the telescope at a distant object;
if the
viewfinder image is not sufficiently in focus for your eye, it may
be refocused as follows:
a.
Remove the viewfinder from its mounting bracket (3),
Fig. 8, by slightly unthreading the six alignment screws (2)
and (4), Fig. 8, until the viewfinder can slip out easily.
b.
Loosen the focus lock ring (5), Fig, 8. thereby enabling
rotation of the viewfinder's objective lens cell (6), Fig. 8.
While looking at a distant object through the viewfinder,
rotate the objective lens cell clockwise or counterclockwise
until sharp focus is achieved.
c.
Tighten the focus lock ring (5), Fig. 8, to lock the focus in
place.
d.
Replace the viewfinder into its bracket (3), Fig. 8, on the
main telescope.
Note: No focusing is possible (or required) from the eyepiece
end of the viewfinder.
2. Alignment of the Viewfinder
In order for the viewfinder to be useful, it must first be aligned
with the main telescope, so that both the viewfinder and the
main telescope are pointing at precisely the same place.
To
align the viewfinder, follow this procedure:
a.
The viewfinder bracket includes six alignment screws.
Turn the three rear alignment screws (2). Fig, 8, roughly
centering the viewfinder within its bracket (as viewed from
the eyepiece-end of the telescope).
When centered,
tighten the knurled lock nut on each of the three rear
alignment screws until the lock nuts are flush against the
bracket ring.
b.
Using the standard equipment PL 25mm eyepiece, point
the main telescope at some easy-to-locate, well-defined.
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