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Finder base
mounting
holes
Focus wheel
Millimeter scale
1.25" adapter thumbscrew
Figure 2.
The 2" dual-speed Crayford focuser
use of optional Eyepieces, Diagonal, and Finder
scope
The Premium 102mm ED does not come with a finder scope,
diagonal or eyepieces in order to grant the user the greatest
versatility in customizing the instrument to suit their tastes.
However, certain rules for using accessories still apply.
You can attach an optional Orion dovetail mounting base to
the telescope in order to attach a finder scope. To install the
dovetail mounting base, remove the two screws located off to
the side of the focuser (Figure 2). Position the dovetail finder
scope base above the exposed threaded holes, and attach
the base to the tube using the two flat head Phillips machine
screws provided with the refractor. Any Orion finder scope with
a dovetail bracket will fit into the dovetail mounting base.
The Premium 102mm ED refractor can use almost any 2"
diagonal and eyepiece. To install a diagonal, unthread the
thumbscrew on the focuser drawtube (Figure 2) until the
internal brass ring is flush with the interior of the drawtube.
Insert the diagonal and secure it with the thumbscrew, which
will compress the brass ring around the inserted barrel of
the diagonal. Then insert an eyepiece into the diagonal and
secure it with the thumbscrew(s) on the diagonal.
use of 1.25" Eyepieces and Diagonals
If you wish to use 1.25" eyepieces and/or a 1.25" diagonal
with the Premium 102mm ED, the 1.25" eyepiece adapter is
required (Figure 3). 1.25" eyepieces usually allow higher mag-
nification than 2" eyepieces. This is especially desirable for
high power observation of objects in our solar system such as
the Moon and planets.
To use 1.25" accessories, simply insert the 1.25" eyepiece
adapter into the drawtube as you would a 2" accessory. Be
sure to secure the adapter in place with the thumbscrew on
2
Rotation
lock thumb-
screw
Focus wheel
Fine focus wheel
Drawtube thumbscrew
Thumbscrew
Figure 3.
The 1.25" eyepiece adapter
the drawtube. You can now insert a 1.25" accessory into the
adapter for use.
the 2" Dual‑speed crayford Focuser
The Premium 102mm ED comes equipped with a dual-speed
Crayford focuser. The Crayford design allows for smooth,
precise focusing without any image shift that typical rack-and-
pinion designs experience.
The focuser features dual-speed adjustment with the fine
focus wheel (Figure 2). This small black wheel allows precise
focus adjustment at a ratio of 11:1, meaning eleven turns of
the fine focus wheel equals one turn of the focus wheel. Use
the focus wheels to achieve rough focus on your target object,
then use the fine focus wheel for the most precise focus in
order to coax out even more image detail. You'll be amazed at
the amount of detail fine focus adjustments allow you to view
on targets such as the lunar surface, planets, star clusters,
and other celestial objects.
If you find that the focus wheels are too tight or too loose, you
can make adjustments to the drawtube tension by using the
drawtube tension adjustment set screw located on the bottom
of the focuser between the focus wheels. Make adjustments
to this set screw with the provided hex key until the focuser
motion feels comfortable. Please note that you must have at
least some tension applied to the focuser drawtube or else it
will not move when you turn the focus wheels.
Once you have achieved focus, you can lock the focuser in
place by tightening the focus lock thumbscrew located on the
bottom of the focuser between the focus wheels (Figure 1).
Locking the focuser in place can be especially useful for imag-
ing applications. Be sure to loosen the focus lock thumbscrew
before making additional focus adjustments.
The focuser drawtube is labeled with a millimeter scale to be
used as a reference (Figure 2). This scale can be useful to
quickly reach focus on previously viewed objects. When initial-
ly observing (or imaging) an object with the Premium 102mm
ED, make a note of the scale marker position once the object
is in focus. When you view the same object during a different
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