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13
DSX-90 Viewfinder
1. Remove the viewfinder by slightly
unthreading the four alignment
screws (4 and 6, Fig. 12) and
slipping it out of the bracket.
2. Loosen the knurled lock-ring (2,
Fig. 12) located near the
viewfinder’s front lens cell (1, Fig.
12). Unthread this ring
(counterclockwise, as seen from
the eyepiece-end of the
viewfinder) by several turns.
3. Look through the viewfinder and
focus on a distant object. Slowly
rotate the front lens cell in one
direction or the other, until the
object appears sharp. One or two
rotations of the lens may have a
significant effect on image focus.
4.Lock the focus in place by
threading the knurled lock-ring clockwise up against the viewfinder’s lens cell.
5. Replace the viewfinder into the viewfinder bracket. Gently tighten the six alignment screws.
Proceed with Aligning the Viewfinder.
DSX-125EC Viewfinder
Turn the focus ring (2, Fig. 12) at the base of the viewfinder eyepiece (3, Fig. 12) in either
direction until a sharp focus is reached.
Aligning the Viewfinder:
It is recommended that you perform steps 1 through 4 of this procedure during the daytime and
step 5 at night.
1. Loosen the tripod base lock knob (16, Fig. 1a) and the Altitude lock (B, Fig. 1b), by
turning the lock about one turn counterclockwise, permitting the telescope to move freely
on its axes.
2. If you have not already done so, place a low-power (e.g., 26mm) eyepiece in the eyepiece
holder of the main telescope (2, Fig. 1d) and point the telescope at an easy-to-find land
object (e.g., the top of a telephone pole). Turn the focuser knob (1, Fig. 1d) so that the
image is sharply focused. Center the object precisely in the main telescope’s field of view.
3. Re-tighten the tripod base lock knob (16, Fig. 1a) and the Altitude lock (B, Fig. 1b).
4. Then, looking through the viewfinder, turn some or all of the viewfinder’s alignment screws
(5, Fig. 1d, also see 4 and 6, Fig 12) until the viewfinder’s crosshairs point precisely at
the same object as centered in the main telescope. The viewfinder is now aligned to the
main telescope. The right-hand image in Fig. 13A shows an object centered in the main
telescope before the viewfinder (the left-hand image) has been aligned to the main
telescope. Fig. 13B shows these same images after the viewfinder and main telescope are
aligned.
5. Check this alignment on a celestial object, such as the Moon or a bright star, and make
any necessary refinements.
Choosing an Eyepiece
A telescope’s eyepiece magnifies the image formed by the telescope’s main optics. Each
eyepiece has a focal length, expressed in millimeters, or “mm.” The smaller the focal length,
the higher the magnification. For example, an eyepiece with a focal length of 9mm has a high-
er magnification than an eyepiece with a focal length of 26mm.
NEVER
point the
telescope
directly at
or near the Sun at any
time! Observing the
Sun, even for the
smallest fraction of a
second, will result in
instant and irre-
versible eye damage,
as well as physical
damage to the tele-
scope itself.
Telescope
Viewfinder Eyepiece
A. Not aligned
B. Aligned
Fig. 13: Aligning the
viewfinder.
Fig. 12:The Viewfinder assembly. (1) Front lens cell; (2)
Knurled lock-ring (DSX-90) or focus ring (DSX-125); (3)
Viewfinder eyepiece; (4) Front alignment screws (one not
visible in photo); (5) Viewfinder bracket; (6) Rear alignment
screws.
DSX-90
DSX-125
d
c
e
b
d
f
c
g