Orion 8881 - Manual

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Congratulations on your purchase of a quality Orion 2" dual-
speed low-profile Cray ford focuser. This focuser is intended
for use with 6" to 12" aperture Newtonian reflectors. If you
do not have a Newtonian reflector, the focuser may not be
appropriate for your telescope.
Crayford focusers generally perform better than rack-and-
pinion models because the design eliminates “focus shift”.
Focus shift is when an image moves position in the eyepiece
when it is being focused. This is very hard to eliminate in
rack-and-pinon focusers due to slight gear and tolerance
imperfections which cause the drawtube to move slightly left
or right when focusing. For the Crayford design, the drawtube
is constantly tensioned (by the focusing shaft and four “roller
bearings”) so the drawtube cannot move perpendicular to the
desired motion.
The 2" Dual-Speed Low-Profile Crayford focuser provides
the most focus range for accessories that require extra in-
travel. With a minimum focus height of 43mm, this focuser is
an excellent choice for any astrophotographic system. The
strong machined aluminum construction supports heavy
2" eyepieces as well as heavy camera bodies. The smooth
focus motion and fine-focus wheel allow precision adjust-
ments for critical focusing of eyepieces and cameras. Installation
This focuser was designed to be a “drop-in” replacement
for the 2" focuser that comes standard on Orion 8" and 10"
reflectors, including IntelliScope and Classic Dobsonians. If
you have one of these telescopes, installing the 2" Crayford
will be easy. You will need a Phillips head screwdriver and
an adjustable crescent wrench or pliers. Use the following
procedure:
1. Position your Newtonian reflector optical tube so it is hori-
zontal. This will prevent any screws or nuts from falling
onto the primary mirror.
2. From the inside of the tube, secure one of the four focuser
securing nuts with the wrench or pliers.
3. Use the screwdriver to completely unthread the focuser
attachment screw from the securing nut currently being
held by the wrench or pliers.
4. Repeat this for the other three nut and screw pairs.
5. Remove the 2" focuser from the tube.
6. Place the 2" dual-speed low-profile Crayford focuser
where the other focuser was previously. Orient the
focuser the same as the removed one was. The through
holes in the base of the focuser should line up with the
holes in the telescope tube.
Figure 1. The Orion 2" dual-speed low-profile Crayford focuser for Newtonian reflectors.
IN 316 Rev B 02/09
Orion 2" Dual-Speed Low-Profile Crayford Focuser
for Newtonian Reflectors
#8881
Eyepiece thumbscrew
1.25" eyepiece adapter
Drawtube extension thumbscrew
Focus wheel
Fine focus wheel
Focus wheel
Drawtube tension adjustment screw
Focus lock thumbscrew
1.25" eyepiece adapter