Figure 13. The tilt of the secondary mirror is adjusted with a 2mm Allen wrench on the three setscrews surrounding the center Phillips-head bolt.

Figure 14. The tilt of the primary mirror is adjusted by turning one or more of the three large, spring-loaded collimation knobs. The three thinner thumbscrews lock the primary mirror in place.

of the three alignment set screws by, say, one full turn, and then tighten the other two to take up the slack (Figure 13). Do not loosen the center screw during this process. The goal is to center the primary mirror reflection in the secondary mir- ror, as in Figure 8d. When it is centered, you’re done adjust- ing the secondary mirror. Don’t worry that the reflection of the secondary mirror (the dark circle with the four spider vanes adjoining it) is off-center, since that adjustment is made when aligning the primary mirror in the next step.

Aligning the Primary Mirror

The final collimation adjustment is made to the primary mir- ror. It will need adjustment if, as in Figure 8d, the secondary mirror is centered under the focuser and the reflection of the primary mirror is centered in the secondary mirror, but the reflection of the secondary mirror (dark circle containing the light reflective surface and center black “dot” of the collimation cap) is off-center.

The tilt of the primary mirror is adjusted with three spring- loaded collimation knobs on the back end of the optical tube (bottom of the primary mirror cell); these are the larger knobs (Figure 14). The other three smaller thumbscrews lock the mirror’s position in place; these thumbscrews must be loos- ened before any collimation adjustments can be made to the primary mirror.

To adjust the primary mirror’s tilt, first loosen all three locking (thin) thumbscrews by turning them counterclockwise a cou- ple of turns each. Now, while looking into the focuser through the collimation cap, turn one of the larger collimation knobs a half turn or so in either direction and see if the secondary mirror reflection moves closer to the center of the primary. That is, does the “dot” of the collimation cap appear to move closer to the ring on the center of the primary mirror? If it does, great, keep going until you get it as close as you can. If it doesn’t, try turning the collimation knob in the opposite direction. If turning the one knob does not seem to bring the dot closer to the ring, try using one of the other collimation

knobs. It will take some trial-and-error using all three collima- tion knobs to properly align the primary mirror. Over time you will get the feel for which collimation knobs to turn to move the image in a given direction.

When you have the dot centered as much as possible in the ring, your primary mirror is collimated. Now lightly tighten the three locking thumbscrews to secure the primary mirror in place.

The view through the collimation cap should now resemble Figure 8e. A simple star test will indicate how well the tele- scope optics are collimated.

Star-Testing the Telescope

When it is dark, point the telescope at a bright star and accu- rately center it in the eyepiece’s field of view. (To achieve focus with an eyepiece, you will likely have to use the included 35mm extension adapter, as described previously.) Slowly de-focus the image with the focusing knob. If the telescope is correctly collimated, the expanding disk should be a perfect circle (Figure 15). If the image is unsymmetrical, the scope is out of collimation. The dark shadow cast by the second- ary mirror should appear in the very center of the out-of-focus circle, like the hole in a donut. If the “hole” appears off-center, the telescope is out of collimation.

If you try the star test and the bright star you have selected is not accurately centered in the eyepiece, the optics will always appear out of collimation, even though they may be perfectly aligned. It is critical to keep the star centered, so over time you will need to make slight corrections to the telescope’s position in order to account for the sky’s apparent motion. Point the telescope at Polaris (the north star) if you do not have a mount that tracks.

3. Care & Maintenance

Give your telescope reasonable care and it will last a lifetime. When not in use, keep its dust cover on as well as the dust

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Orion #8297 8 F/3.9, #8296 10 F/3.9 Care & Maintenance, Aligning the Primary Mirror, Star-Testing the Telescope
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#8296 10" F/3.9, #8297 8" F/3.9 specifications

The Orion #8297 8" F/3.9 and #8296 10" F/3.9 reflect the latest innovations in astronomical technology, designed to meet the needs of both amateur and professional astronomers. These telescopes are renowned for their impressive optics, portability, and user-friendly features, making them ideal for deep sky observation and astrophotography.

The Orion #8297 8" F/3.9 features an 8-inch aperture, which allows for a remarkable light-gathering capacity, making it suitable for observing faint celestial objects. With a fast focal ratio of F/3.9, this telescope enables astronomers to capture stunning images of galaxies, nebulae, and star clusters with minimal exposure times. The telescope’s well-constructed primary mirror is made from high-quality glass, ensuring sharp and detailed views of the night sky. Additionally, the dual-speed 2” Crayford-style focuser enhances focusing precision, allowing users to achieve fine adjustments with ease.

On the other hand, the Orion #8296 10" F/3.9 elevates the observational experience with a larger 10-inch aperture. This increased size further enhances light-gathering ability, resulting in even clearer images of distant objects. Like its 8-inch counterpart, the F/3.9 focal ratio makes this telescope particularly advantageous for astrophotography, enabling users to shoot spectacular deep-sky images efficiently. The telescope is constructed with a sturdy, fully adjustable mount that ensures stability while tracking celestial objects, even during high-magnification viewing.

Both models come equipped with adjustable finderscopes, which assist in locating objects in the vast night sky, and they include a set of high-quality eyepieces that provide a range of magnifications to suit different observation needs. Furthermore, the lightweight design of both telescopes allows for easy transport to various observing sites, making them versatile tools for astrophotography enthusiasts and casual observers alike.

In summary, the Orion #8297 8" F/3.9 and #8296 10" F/3.9 are excellent telescopes that combine advanced optics with user-centric design. Their strong performance, portability, and innovative features make them perfect choices for anyone looking to explore the wonders of the universe, from novices to seasoned astronomers.
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