Figure 13. The tilt of the secondary mirror is adjusted with a 2mm Allen wrench on the three setscrews surrounding the center
Figure 14. The tilt of the primary mirror is adjusted by turning one or more of the three large,
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
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
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
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
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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