Adjusting the Primary Mirror

Figure 14. To center the secondary mirror under the focuser, hold the secondary mirror holder in place with one hand while adjusting the center bolt with a Phillips screwdriver. Do not touch the mirror’s surface!

Figure 15. Adjust the tilt of the secondary mirror by loosening or tightening the three alignment set screws with a 2mm hex key.

Figure 16. The three small thumbscrews that lock the primary mirror in place must first be loosened before any adjustments can be made.

Figure 17. The tilt of the primary mirror is adjusted by turning one or more of the three larger thumbscrews.

possible. It may not be perfectly centered, but that is OK. Now tighten the three small alignment screws equally to secure the secondary mirror in that position. If the entire primary mirror reflection is not visible in the secondary mirror, as in Figure 13c, you will need to adjust the tilt of the secondary mirror. This is done by alternately loosening one of the three align- ment setscrews while tightening the other two, as depicted in Figure 15. The goal is to center the primary mirror reflection in the secondary mirror, as in Figure 13d. Don’t worry that the reflection of the secondary mirror (the smallest circle, with the collimation cap “dot” in the center) is off-center. You will fix that in the next step.

The final adjustment is made to the primary mirror. It will need adjustment if, as in Figure 13d, the secondary mirror is cen- tered under the focuser and the reflection of the primary mirror is centered in the secondary mirror, but the small reflection of the secondary mirror (with the “dot” of the collimation cap) is off-center.

The tilt of the primary mirror is adjusted with three spring- loaded collimation thumbscrews on the back end of the optical tube (bottom of the primary mirror cell); these are the larger

thumbscrews. 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 start, turn the smaller thumbscrews a few turns each (Figure 14). Use a screwdriver in the slots, if necessary.

Now, try tightening or loosening one of the larger collima- tion thumbscrews with your fingers (Figure 17). Look into the focuser and see if the secondary mirror reflection has moved closer to the center of the primary. You can tell this easily with the collimation cap and mirror center mark by simply watching to see if the “dot” of the collimation cap is moving closer or farther away from the ring on the center of the primary mir- ror. When you have the dot centered as much as possible in the ring, your primary mirror is collimated. The view through the collimation cap should resemble Figure 13e. Retighten the locking thumbscrews.

A simple star test will tell you whether the optics are accurately 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. Slowly de-focus

XT10 CLASSIC, XT8 CLASSIC specifications

The Orion XT10 Classic and XT8 Classic telescopes represent a perfect blend of innovative design and advanced optics, making them excellent choices for amateur astronomers. Both models are part of Orion's popular XT Classic series, known for their user-friendly features and high-quality performance.

The Orion XT10 Classic features a large 10-inch aperture, providing exceptional light-gathering capabilities. This allows users to observe faint celestial objects, such as distant galaxies, nebulae, and star clusters, with remarkable clarity and detail. The telescope's Dobsonian mount ensures smooth and stable movement, making it easy to track objects across the night sky.

The XT8 Classic, with its 8-inch aperture, also offers impressive light-gathering ability, delivering crisp views of various astronomical phenomena. Both models are equipped with a parabolic mirror design, which minimizes optical aberrations and enhances image quality. This design is a significant advancement over traditional spherical mirrors, allowing for sharper and more focused images.

One of the standout features of both Telescopes is their simplicity of use. The intuitive Dobsonian mounting system allows users to easily position the telescope and locate celestial objects without the complexity of motorized tracking systems. This makes them ideal for novices as well as experienced astronomers looking for a portable option.

Both models come with a sturdy, pre-assembled base, ensuring stability during observations. The XT10 Classic and XT8 Classic also include high-quality eyepieces, which enhance viewing experiences. Optional accessories, such as additional eyepieces and filters, can further expand the observational capabilities.

The Orion XT10 Classic offers a focal length of 1200mm, while the XT8 Classic has a focal length of 1200mm as well. This allows both telescopes to excel in a variety of observational scenarios, from lunar observations to deep-sky exploration. Additionally, both telescopes feature a single-focal point, which makes them compatible with numerous aftermarket eyepieces.

In summary, the Orion XT10 Classic and XT8 Classic telescopes are distinguished by their user-friendly design, exceptional optical performance, and robust construction. They are perfect for anyone interested in exploring the wonders of the universe, providing a gateway to breathtaking views of the night sky. Whether you choose the larger XT10 Classic or the more compact XT8 Classic, both models are bound to enhance your astronomical experience.