Orion 8956, 8958 User Manual

INSTRUCTION MANUAL

Orion® Ritchey-Chrétien

Astrographs

#8956 6" f/9 Ritchey-Chrétien Optical Tube Assembly

#8958 8" f/8 Ritchey-Chrétien Optical Tube Assembly

#8956

#8958

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IN 361 Rev. A 9/09

Optical tube

Collimating eyepiece

Figure 1:

The Ritchey-Chrétien Optical Tube (6" shown)

Congratulations on your purchase of an Orion
Ritchey-Chrétien astrograph! Astroimaging

demands high contrast and center to edge image
sharpness. The Ritchey-Chrétien optical sys­tem features precision hyperbolic mirrors with an
impressive reflectivity rating of no less than 94%.
These highly corrected optics offer virtually coma­free performance; and multiple knife-edge baffles
provide images with superb contrast. These design
features will offer a lifetime of outstanding perfor­mance for imaging and visual applications. The
Ritchey-Chrétien is a member of the Cassegrain
family of telescopes. This unique design offers
large-diameter optics while maintaining very short
tube lengths, making them extremely portable and
versatile.

Parts List

1 Optical tube assembly

1 2" Extension ring

2 1" Extension rings

1 Collimation eyepiece

Extension rings

Unpacking Your Telescope

Use care when unpacking the shipping carton. We recom­mend keeping the boxes and all original packaging materi­als. In the event that the telescope needs to be shipped to
another location, or returned for warranty repair, having the
proper packaging will ensure that your telescope will survive
the journey intact. Returns for refund or exchange will not be
accepted without all of the original packaging.

Your new telescope arrives double-boxed (Figures 2a-d). Make
certain you are opening from the top of the box to access the
accessories packaged in the Styrofoam shell. To access the
optical tube simply grasp the Styrofoam piece and lift it out of
the box and set it aside for the time being. Once all items have
been removed from the box take a moment to confirm that all
pieces are present and intact. Refer to the Parts List to aid in
identifying the various pieces.

Setting Up Your Telescope

Your Ritchey-Chrétien optical tube comes ready to use right
out of the box. The focuser is attached to the optical tube and
ready to accept either visual or photographic accessories.
Also included are three individual extension rings (Figure 1).
These extension rings are provided to allow multiple visual or
photographic accessories to reach focus. These are designed

2

2a

2b

2c

2d

Grip-ring

Focuser
body

Figure 3:

Removing the focuser.

to thread directly onto the optical tube. It may be useful to
experiment with different combinations during the day before
heading out into the field. Choose a target over ½ mile away
to ensure you are simulating distant focus.

If the focuser drawtube is fully extended and you are still
unable to achieve focus you will need to install one or more
of these extension rings. They are to be installed in-between
the focuser and optical tube. In order to install the necessary
extension ring(s) you will need to first remove the focuser from
the optical tube. Be careful not to cross-thread these pieces
when re-attaching adapters.

1. Remove the focuser by holding the focuser body with one
hand while gently turning the knurled silver grip-ring with
the other (Figure 3). Turn counter-clockwise to loosen.

2. Attach the extension ring of choice to the back end of
the tube. The optical tube has external (male) threads.
Subsequently you will use the end of the ring with internal
(female) threads to attach.

3. The exposed threads on the back of the extension rings
match that on the OTA to install additional extension rings
or to reattach the focuser.

4. Once you have added the desired number of extension
rings re-attach the focuser by aligning the silver grip-ring
over the exposed extension ring threads and tighten by
carefully turning clockwise (Figure 4a-d).

The wide variety of astronomical equipment available will
require that you add or remove some or all of the extension
rings. Individual setups will require different combinations of
extension rings be used. In general, visual applications will
require further extension than imaging. The examples listed
and pictured below are of common scenarios. Some set­ups may require combinations different from those shown in
Figure 4.

To set up any Orion StarShoot Deep Space imagers use all
three (1 x 2" and 2 x 1") of the supplied extension rings to
reach focus. For DSLR and most visual applications use 3" of

Figures 2a-d: Unpacking the Optical Tube.

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