Orion #9781 EON 72MM - Manual (Page 3)

3
2" Dual-Speed Crayford Focuser
The high quality dual-speed 2" Crayford focuser is one of
the most important components of your EON refractor. The
Crayford design allows for smooth, precise focusing without
any image shift that typical rack-and-pinion designs experi-
ence.
For quick focusing of your EON refractor, the two larger
focus knobs will provide a coarse focus. For more precise
focusing, as needed for applications such as critical high
power planetary observing and digital imaging, the smaller
black focus knob (Figure 1a) offers fine focus adjustment.
The fine focus knob rotates eleven times to one single rota-
tion of the coarse focus knobs, making an 11:1 ratio for
extremely precise focusing.
The dual-speed Crayford is capable of handling the weight
of heavy accessories, such as large 2" eyepieces or a CCD
or DSLR camera. Adding tension to the focuser drawtube
will further increase the amount of weight the focuser can
handle without slipping. To adjust the focuser drawtube ten-
sion, locate the focus tension set screw on the underside
of the focuser (Figure 3). Using the 2.5mm hex key, turn
the set screw clockwise until you have added the appropri-
ate amount of tension for your needs. In some cases, you
may want to loosen the tension, which will also decrease
the resistance of the focus knob movement. Simply turn the
focus tension set screw counter-clockwise as needed to
loosen the focus drawtube tension.
Tightening the focus lock thumbscrew (Figure 3) will prevent
the drawtube from moving. This feature can be utilized for
imaging, or visual use, when you have achieved focus and
do not want the drawtube to move. While you are focusing,
make sure the focus lock thumbscrew is loosened, or the
drawtube may not move properly.
Note: Applying too little tension on the focuser will result in
the focus drawtube to slide under its own weight, or under
the weight of your accessories installed. Make sure there is
enough tension to support your 2"or 1.25" accessories.
Focuser rotation
The focuser assembly on the EON refractors have the abil-
ity to be rotated. Under normal use, you should not have
to rotate the focuser, since the eyepiece and diagonal can
be rotated instead. However, focuser rotation can be ben-
eficial for changing the camera orientation while imaging
(see “Imaging with the EON Refractors”). Additionally, this
feature can allow you to keep the focus knobs parallel to the
ground no matter how your telescope is positioned. This can
be especially convenient when the telescope is mounted in
different orientations, causing the focus knob orientation to
change.
To rotate the focuser, turn the focus rotation lock ring (Figure
1a) counter-clockwise until the assembly loosens. Rotate the
focuser to the desired orientation. Lock the focuser in place
by turning the focus rotation lock ring clockwise. To ensure
a secure lock, it is sometimes necessary to grab hold of
the entire focuser assembly and firmly rotate it clockwise,
bracing your other hand against the stationary portion of the
optical tube.
The 72mm EON refractor has screw holes for an optional
finder scope dovetail base attached to the rotating portion
of the focuser, allowing you to change the orientation of the
finder scope as desired.
The EON 72mm uses a single thumbscrew instead of a
lock ring to lock the focuser rotation. To rotate the focuser
on the EON 72mm, loosen the focuser rotation lock thumb-
screw and rotate the focuser to the desired orientation. Lock
the focuser in place by tightening the focuser rotation lock
thumbscrew.
using 1.25" and 2" accessories
Your EON refractor can accommodate both 1.25" and 2"
accessories, including just about any eyepiece, diagonal,
or camera. The Crayford focuser has a 2" eyepiece holder
with a 1.25" eyepiece adapter installed (Figure 4). Both the
2" eyepiece holder and 1.25" eyepiece adapter feature a
brass compression ring to hold your accessories in place.
The brass compression ring securely holds the 1.25" or 2"
accessory in place without marking its metal barrel.
The telescope must be used with either a diagonal or exten-
sion tube in order for the eyepiece to reach focus. In most
cases, you will be using a 90° star diagonal for visual use
with an eyepiece.
To attach a 1.25" diagonal or extension tube to your tele-
scope:
1. Remove the dust cap from the 1.25" eyepiece adapter.
2. Insert the barrel of your diagonal or extension tube
into the 1.25" eyepiece adapter.
Figure 3. Adjustments can be made to the focus tension set
screw using the provided 2.5mm hex key. Tightening the focus lock
thumbscrew will stop the focuser drawtube from moving.
Focus tension set
screw
Focus lock thumbscrew