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

  Astroimaging 

demands high contrast and center to edge image 
sharpness.  The  Ritchey-Chrétien  optical  sys-
tem features precision hyperbolic mirrors with an 
impressive reflectivity rating of no less than 94%. 
These highly corrected optics offer virtually coma-
free performance; and multiple knife-edge baffles 
provide images with superb contrast. These design 
features will offer a lifetime of outstanding perfor-
mance  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

Unpacking Your Telescope

Use care when unpacking the shipping carton. We recom-
mend keeping the boxes and all original packaging materi-
als. 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 

Figure 1: 

The Ritchey-Chrétien Optical Tube (6" shown)

Collimating eyepiece

Extension rings

Optical tube

Summary of Contents for 8956 Instruction manual

Page 1: ...lescope com Corporate Offices 831 763 7000 89 Hangar Way Watsonville CA 95076 Orion Ritchey Chrétien Astrographs 8956 6 f 9 Ritchey Chrétien Optical Tube Assembly 8958 8 f 8 Ritchey Chrétien Optical Tube Assembly Providing Exceptional Consumer Optical Products Since 1975 OrionTelescopes com 8956 8958 ...

Page 2: ...ds 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 S...

Page 3: ...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 ...

Page 4: ...sion 1 extension Optical tube Optical tube Optical tube DSLR camera body DSLR Camera Configuration StarShoot Deep Space Imager Configuration Standard Visual Configuration 4a 4b Off axis guider StarShoot CCD Imager Focuser 2 extension Optical tube StarShoot with Off Axis Guider Configuration 4c 4d Figure 4a d Typical visual and imaging configurations for the Ritchey Chrétien optical tube ...

Page 5: ...g a similar bracket Installing a finder scope is very simple 1 Loosen the metal thumbscrew on the side of the dovetail base 2 Insert the bracket into the dovetail from the back of the telescope until it stops 3 When the finder bracket is securely in place retighten the metal thumbscrew Inserting a Star Diagonal A star diagonal is a prism that diverts the light at a right angle to the light path of...

Page 6: ...by a thin white circle on the outer edge You can disregard that for the time being it will be covered in the following section If this is aligned as in Figure 9a no further adjustments will be necessary If it appears as in Figure 9b with the dot of the collimation eyepiece not centered in the secondary center mark adjust the three collimation screws at the front of the secondary mirror holder This...

Page 7: ...r cen tered in your field of view Furthermore seeing conditions will affect the end result Keeping the star precisely centered in the field of view is critical to avoid false negatives It is sug gested that you choose a star close to the zenith straight overhead rather than at the horizon to minimize atmospheric distortions Using Polaris as your target star can be helpful as minimal drift adjustme...

Page 8: ...ey Chrétien Figure Hyperbolic Mirror material BK 7 Mirror Coating Enhanced no less than 94 with SiO2 Overcoat Focuser Machined Aluminum Dual Speed 10 1 Linear Bearing Crayford Accessories Accepts 2 1 25 Baffles 8 knife edge baffles Optical Tube Steel Aperture 150mm 6 Focal Length 1370 mm Focal Ratio f 9 Secondary Mirror Minor Axis 67mm Length 406mm Diameter 193mm Weight 12 4 lbs Specifications 8 f...

Page 9: ...age paid to Orion Warranty Repair 89 Hangar Way Watsonville CA 95076 Proof of purchase such as a copy of the original receipt is required This warranty does not apply if in Orion s judgment the instrument has been abused mishandled or modified nor does it apply to normal wear and tear This warranty gives you specific legal rights and you may also have other rights which vary from state to state Fo...

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