Orion 8296, 8297 User Manual

INSTRUCTION MANUAL

Orion 8" and 10" f/3.9

Newtonian Astrographs

#8297 8" f/3.9, #8296 10" f/3.9

Providing Exceptional Consumer Optical Products Since 1975

OrionTelescopes.com

#8296

Customer Support (800) 676-1343 • E-mail: support@telescope.com

Corporate Offic es (83 1) 763 -70 00 • 89 Hangar Way, Watsonville, CA 95076

IN 406 Rev. A 07/11

9x50 Finder Scope

Finder scope bracket

Focus wheel

2" Accessory collar

Tube rings

Optical tube

Drawtube tensioning thumbscrew

Focus wheel

Figure 1. The Orion 8" f/3.9 Newtonian Astrograph

Fine focus wheel

Congratulations on your purchase of an Orion f/3.9 Newtonian Astrograph! These powerful imaging telescopes feature “fast,” high-quality parabolic optics, a 2" dual-speed Crayford focuser, and excellent mechanical construction with some special features. Optimized for astrophotography with DSLR and astronomical CCD imaging cameras, our f/3.9 Newtonian Astrographs are capable of delivering breathtaking imaging performance – for beginning to advanced astrophotographers.

This instruction manual covers both the 8" and 10" models of f/3.9 Newtonian astrograph. Although they differ in aperture and focal length, physical size, and weight, they are otherwise very similar in mechanical construction and features. So we will use the 8" model to illustrate the features of both astrographs. Any exceptions related to the 10" model will be noted. This instruction manual will help you to set up and properly use your telescope. Please read it through completely before attempting to use the scope and its included accessories.

WARNING: Never look directly at the Sun through your telescope or its finder scope – even for an instant – without a professionally made solar filter that completely covers the front of the instrument, or permanent eye damage could result. Young children should use this telescope only with adult supervision.

Parts List

• Optical tube assembly

• Optical tube dust cap

• 1.25" eyepiece holder

• 9x50 finder scope with bracket

• Pair of hinged tube rings

• 2" thread-on extension adapter, 30mm

• 2" slip-on extrension adapter, 36mm

• Quick collimation cap

• Cooling accelerator fan and battery holder (batteries not

included)

• Starry Night Special Edition CD-ROM and StarTheater DVD

We recommend keeping all of the original packaging. In the unlikely event you should need to ship the telescope back to Orion for warranty repair service, you should use the original

1.25" Eyepiece holder Accessory lock thumbscrews

2" Accessory collar

Eyepiece lock thumbscrews

Drawtube tensioning thumbscrew

Coarse focus wheels

11:1 Fine focus wheel

Figure 2. The 2" dual-speed (11:1) Crayford focuser

packaging to ensure the telescope stays intact during shipping. Take a moment to inspect the telescope and all of its parts.

Before proceeding with the instructions, refer to Figure 1 to familiarize yourself with some of the features and components of the telescope.

1. Getting Started

The telescope arrives nearly fully assembled from the factory, with optics installed, in a single shipping box. The optics were collimated at the factory, however you should check the collimation prior to first use (see “Collimating the Optics”), as it’s not uncommon for Newtonian optics to get bumped slightly out of collimation in the delivery process. Likely only a minor adjustment, if any, may be necessary.

Attaching the Telescope to a Mount

The f/3.9 Newtonian Astrographs each come with a pair of hinged, felt-lined tube rings to hold the optical tube assembly (OTA) on a mount. Each ring has a flat boss on opposing sides. Both bosses have a ¼"-20 threaded hole in the center. One tube ring has a piggyback camera adapter mounted on one of the bosses, which can be used to mount a camera for piggyback astrophotography. That adapter can be removed if you wish to attach an optional dovetail plate to the top of the tube rings for mounting a piggybacked guide scope.

The tube rings should be attached to a dovetail mounting plate (sold separately) compatible with your mount’s equatorial head. Balancing the telescope is achieved by sliding the dovetail mounting plate forward or backward within the mount’s dovetail saddle. You can also move the telescope forward or backward within the tube rings. To do so, loosen the tube ring clamps slightly and slide the telescope tube forward or backward as needed to reach optimum balance,

then retighten the clamps. Rotating the telescope to achieve a comfortable eyepiece or camera angle is done in the same fashion. Simply loosen the tube ring clamps just enough to allow the optical tube to rotate within the tube rings. Retighten the tube ring clamps securely once you have reached the desired eyepiece or camera orientation.

2" Dual-Speed Crayford Focuser

The f/3.9 Newtonian Astrograph features an all-metal, 2" dual-speed (11:1) Crayford-type focuser (Figure 2), which allows very precise, fine focusing. A reinforcing plate inside the optical tube just under the focuser provides added rigidity, minimizing any “flexing” of the focuser housing on the tube due to the weight and moment arm of the imaging camera. If the drawtube slips under the weight of your imaging system or heavy visual accessories, simply increase the drawtube tension by gently tightening the drawtube tensioning thumbscrew as needed.

The smooth focus motion and fine-focus wheel allow precision adjustments for critical focusing of eyepieces and cameras. Once focus is reached, you can lock the drawtube in place by tightening the drawtube tensioning thumbscrew.

The focuser drawtube has a 2" collar on the end of it, with two thumbscrews, for attachment of 2" accessories. The telescope ships with a 1.25" eyepiece holder inserted into the 2" collar.

The focuser drawtube has 38mm of travel.

Fine Focus

The dual-speed Crayford focuser features both coarse and fine focusing wheels. The two large, silver-colored wheels are for coarse focusing. The small black wheel next to the righthand large focus wheel allows ultra-precise focus adjustment at a gear ratio of 11:1, meaning eleven turns of the fine focus wheel equals one turn of the large focus wheel.

Use the large focus wheels to achieve rough focus on your target object, then use the fine focus wheel to home in on the exact focus point. You will be amazed at the amount of detail that careful fine focus adjustment brings in to view on targets such as the lunar surface, planets, double stars, and other celestial objects.

Focuser Reinforcing Plate

You’ll notice that on the inside of the optical tube directly under the focuser is a steel reinforcing plate. This plate was added to provide extra rigidity to the interface between the focuser and tube, to minimize the possibility of flexure at that interface due to the weight of the imaging camera and its positional moment arm. Such flexure could cause undesirable distortion in longexposure astrophotographic images. This reinforcing plate allows use of heavier cameras while minimizing the risk of flexure between the focuser base and tube. It is a design enhancement that other, similar scopes on the market do not have.

Attaching the Finder Scope

The included 9x50 crosshair finder scope (Figure 3a) is useful for locating objects in the sky and centering them in the main telescope’s field of view.

To install it, first remove the O-ring from the bracket and place it over the body of the finder scope until it seats in the narrow groove near the middle of the finder. Unthread the two black nylon alignment screws on the bracket until the screw ends are flush with the inside surface of the bracket. Slide the eyepiece end (narrow end) of the finder scope into the end of the bracket’s cylinder opposite the alignment screws while pulling the chrome, spring-loaded tensioning pin on the bracket with your fingers (Figure 3b). Push the finder scope through the bracket until the O-ring seats just inside the front opening. Release the tensioner and tighten the two black nylon screws a couple of turns each to secure the finder scope in place. The tips of the tensioner and nylon screws should seat into the wide groove on the finder scope’s body.

Now slide the foot of the finder scope bracket into the dovetail base on the main telescope. You’ll first have to back out the thumbscrew lock on the dovetail base a few turns to allow the bracket to slide in. Once the bracket is inserted, tighten the thumbscrew lock.

Aligning the Finder Scope

The finder scope and the main telescope must be aligned so they point to exactly the same spot in the sky. Alignment is easiest to do in daylight. First, insert an eyepiece (a crosshair eyepiece is best) into the eyepiece holder in the telescope’s focuser. Point the telescope at an object such as the top of a telephone pole or a street sign that is at least a quartermile away. Move the telescope so the target object appears in the very center of the field of view when you look into the eyepiece.

Now look through the finder scope. Is the object centered in the finder scope’s field of view? If not, hopefully it will be visible somewhere in the field of view, so that only a minor adjustment of the finder scope’s two alignment screws will be needed to center it. Otherwise you’ll have to make coarser adjustments to redirect the aim of the finder scope.

Once the target object is centered on the crosshairs of the finder scope, look again in the telescope’s eyepiece and see if it is still centered there as well. If it isn’t, repeat the entire process, making sure not to move the telescope while adjusting the alignment of the finder scope. When the target object is centered on the crosshairs of the finder scope and in the telescope’s eyepiece, the finder scope is aligned and ready to be used for locating objects.

The finder scope alignment should be checked before every imaging or observing session. This can easily be done at night, before viewing through the telescope. Choose any bright star or planet, center the object in the telescope eyepiece, and then adjust the bracket’s alignment screws until the star or planet is also centered on the finder’s crosshairs.

Finder scope

Figure 3a. The 9x50 finder scope and bracket

Figure 3b. Pull back the spring tensioning pin and slide the finder

scope into its bracket until the O-ring is seated in the bracket ring.

Focusing the Finder Scope

If the image in the finder scope appears out of focus, you will need to refocus the finder scope for your vision. First, loosen the lock ring located behind the objective lens cell on the body of the finder scope (Figure 3a). Back the lock ring off by a few turns. Then refocus the finder scope on a distant object by rotating the objective lens cell clockwise or counterclockwise. Once the image appears sharp, retighten the lock ring behind the objective lens cell. The finder scope’s focus should not need to be adjusted again.

O-ring (not visible)

Focusing lock ring

Dovetail base

Finder scope bracket

Nylon alignment thumbscrew (2)

Eyepiece

Tensioner pin

2. Operating Your Orion f/3.9 Newtonian Astrograph

Your Orion f/3.9 Newtonian Astrograph is designed primarily for astro-imaging, but it makes a fine visual instrument as well. For visual use, we recommend using high-quality eyepieces to take full advantage of the instrument’s exceptional optical quality. For imaging applications, the telescope is optimized for use with an APS-C or smaller size sensor, found in such cameras as the Orion StarShoot™ Pro, Orion Parsec™, and many DSLRs.

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